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Cas Database

100-02-7

100-02-7

Identification

  • Product Name:4-Nitrophenol

  • CAS Number: 100-02-7

  • EINECS:202-811-7

  • Molecular Weight:139.111

  • Molecular Formula: C6H5NO3

  • HS Code:2908.90 Oral rat LD50: 202 mg/kg

  • Mol File:100-02-7.mol

Synonyms:Phenol,p-nitro- (8CI);1-Hydroxy-4-nitrobenzene;4-Hydroxy-1-nitrobenzene;4-Hydroxynitrobenzene;Phenol, 4-nitro-;Niphen;p-Hydroxynitrobenzene;p-Nitrophenol;

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Safety information and MSDS view more

  • Pictogram(s):HarmfulXn,ToxicT,FlammableF

  • Hazard Codes: Xn:Harmful;

  • Signal Word:Warning

  • Hazard Statement:H302 Harmful if swallowedH312 Harmful in contact with skin H332 Harmful if inhaled

  • First-aid measures: General adviceConsult a physician. Show this safety data sheet to the doctor in attendance.If inhaled Fresh air, rest. Refer for medical attention. In case of skin contact Remove contaminated clothes. Rinse and then wash skin with water and soap. Refer for medical attention . In case of eye contact First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention. If swallowed Rinse mouth. Rest. Refer for medical attention . Inhalation or ingestion causes headache, drowsiness, nausea, and blue color in lips, ears, and fingernails (cyanosis). Contact with eyes or skin causes irritation; can be absorbed through skin to give same symptoms as for inhalation. (USCG, 1999) Immediate first aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand-valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR as necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Dinitrophenol and Related Compounds/

  • Fire-fighting measures: Suitable extinguishing media Use water spray, dry chemical, foam, or carbon dioxide. Use water spray to keep fire-exposed containers cool. Approach fire from upwind to avoid hazardous vapors and toxic decomposition products. Fight fire from protected location or maximum possible distance. Special Hazards of Combustion Products: Toxic oxides of nitrogen and fumes of unburned material may form in fires. Behavior in Fire: Decomposes violently at 279°C and will burn even in absence of air. (USCG, 1999) Wear self-contained breathing apparatus for firefighting if necessary.

  • Accidental release measures: Use personal protective equipment. Avoid dust formation. Avoid breathing vapours, mist or gas. Ensure adequate ventilation. Evacuate personnel to safe areas. Avoid breathing dust. For personal protection see section 8. Personal protection: particulate filter respirator adapted to the airborne concentration of the substance. Do NOT let this chemical enter the environment. Sweep spilled substance into covered sealable containers. If appropriate, moisten first to prevent dusting. Carefully collect remainder. Then store and dispose of according to local regulations. Spill or leak procedures: Shovel into suitable dry container.

  • Handling and storage: Avoid contact with skin and eyes. Avoid formation of dust and aerosols. Avoid exposure - obtain special instructions before use.Provide appropriate exhaust ventilation at places where dust is formed. For precautions see section 2.2. Separated from combustible substances, reducing agents and food and feedstuffs. Well closed.... KEEP ALL FLAMMABLES AWAY FROM AREA WHERE OXIDIZING AGENTS ARE STORED. ... AREA ... KEPT COOL & VENTILATED, & SHOULD BE FIREPROOFED.

  • Exposure controls/personal protection:Occupational Exposure limit valuesBiological limit values Handle in accordance with good industrial hygiene and safety practice. Wash hands before breaks and at the end of workday. Eye/face protection Safety glasses with side-shields conforming to EN166. Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU). Skin protection Wear impervious clothing. The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace. Handle with gloves. Gloves must be inspected prior to use. Use proper glove removal technique(without touching glove's outer surface) to avoid skin contact with this product. Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. Wash and dry hands. The selected protective gloves have to satisfy the specifications of EU Directive 89/686/EEC and the standard EN 374 derived from it. Respiratory protection Wear dust mask when handling large quantities. Thermal hazards

Supplier and reference price

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  • Manufacture/Brand:TRC
  • Product Description:4-Nitrophenol
  • Packaging:1g
  • Price:$ 55
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  • Manufacture/Brand:TCI Chemical
  • Product Description:4-Nitrophenol
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  • Manufacture/Brand:TCI Chemical
  • Product Description:4-Nitrophenol
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  • Manufacture/Brand:TCI Chemical
  • Product Description:4-Nitrophenol min. 99.0 %
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  • Manufacture/Brand:TCI Chemical
  • Product Description:4-Nitrophenol
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  • Manufacture/Brand:TCI Chemical
  • Product Description:4-Nitrophenol (0.25% in Water) [for pH Determination]
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  • Manufacture/Brand:Sigma-Aldrich
  • Product Description:4-Nitrophenol certified reference material, TraceCERT
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  • Manufacture/Brand:Sigma-Aldrich
  • Product Description:4-Nitrophenol(Acetaminophen RCF) Pharmaceutical Secondary Standard; Certified Reference Material
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  • Manufacture/Brand:Sigma-Aldrich
  • Product Description:4-Nitrophenol solution 10 mM
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  • Manufacture/Brand:Sigma-Aldrich
  • Product Description:Acetaminophen Related Compound F United States Pharmacopeia (USP) Reference Standard
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Relevant articles and documentsAll total 1912 Articles be found

Catalytic degradation of an organophosphorus agent at Zn-OH sites in a metal-organic framework

Mian, Mohammad Rasel,Islamoglu, Timur,Afrin, Unjila,Goswami, Subhadip,Cao, Ran,Kirlikovali, Kent O.,Hall, Morgan G.,Peterson, Gregory W.,Farha, Omar K.

, p. 6998 - 7004 (2020)

Chemical warfare agents (CWAs), and in particular organophosphorus nerve agents, still pose a significant threat to society due to their continued use despite international bans. While nature has constructed a variety of enzymes that are capable of rapidly hydrolyzing organophosphorus substrates, the poor stability of enzymes outside of buffered solutions has limited their use in practical applications, such as in filters or on protective suits. As a result, we have explored the use of metal-organic frameworks (MOFs) as robust and tunable catalytic materials in which the nodes can be tailored to resemble the active sites found in these enzymes. We identified the Zn-based MOF, MFU-4l, as a promising hydrolysis catalyst due to the presence of Zn(II)-OH groups on the nodes, which are structurally reminiscent of the active sites in carbonic anhydrase (CA), a Zn-based enzyme that has been shown to efficiently catalyze the hydrolysis of phosphate esters. Indeed, MFU-4l can rapidly hydrolyze both the organophosphorus nerve agent, GD, and its simulant, DMNP, with half-lives as low as 1 min, which is competitive with the some of best heterogeneous hydrolysis catalysts reported to date.

Influence of activated carbons on the kinetics and mechanisms of aromatic molecules ozonation

Merle,Pic,Manero,Mathé,Debellefontaine

, p. 166 - 172 (2010)

Companies have been looking for new methods for treating toxic or refractory wastewaters; which can mainly be used prior to or after or in connexion with biological treatment processes. This paper compares conventional ozone oxidation with activated carbo

Biomimicking, metal-chelating and surface-imprinted polymers for the degradation of pesticides

Erdem, Murat,Say, Ridvan,Ers?z, Arzu,Denizli, Adil,Türk, Hayrettin

, p. 238 - 243 (2010)

Molecularly imprinted polymer beads (PIBs) and non-imprinted (control) polymer beads (NIBs) have been prepared from methacryloylhistidine-Co2+, -Ni2+, and -Zn2+ monomers and applied as catalyst in the hydrolysis of paraoxo

A simple DNase model system comprising a dinuclear Zn(II) complex in methanol accelerates the cleavage of a series of methyl aryl phosphate diesters by 1011-1013

Neverov, Alexei A.,Liu, C. Tony,Bunn, Shannon E.,Edwards, David,White, Christopher J.,Melnychuk, Stephanie A.,Brown, R. Stan

, p. 6639 - 6649 (2008)

The di-Zn(II) complex of 1,3-bis[N1,N′1-(1,5,9- triazacyclododecyl)]propane with an associated methoxide (3:Zn(II) 2:-OCH3) was prepared and its catalysis of the methanolysis of a series of fourteen m

Guanidine based self-assembled monolayers on Au nanoparticles as artificial phosphodiesterases

Salvio, Riccardo,Cincotti, Antonio

, p. 28678 - 28682 (2014)

Gold nanoparticles passivated with a long chain alkanethiol decorated with a phenoxyguanidine moiety were prepared and investigated as catalysts in the cleavage of the RNA model compound HPNP and diribonucleoside monophosphates. The catalytic efficiency and the high effective molarity value of the Au monolayer protected colloids points to a high level of cooperation between the catalytic groups.

Structural flexibility enhances the reactivity of the bioremediator glycerophosphodiesterase by fine-tuning its mechanism of hydrolysis

Hadler, Kieran S.,Mitic, Natasa,Ely, Fernanda,Hanson, Graeme R.,Gahan, Lawrence R.,Larrabee, James A.,Ollis, David L.,Schenk, Gerhard

, p. 11900 - 11908 (2009)

The glycerophosphodiesterase from Enterobacter aerogenes (GpdQ) belongs to the family of binuclear metallohydrolases and has attracted recent attention due to its potential in bioremediation. Formation of a catalytically competent binuclear center is prom

A unique nickel system having versatile catalytic activity of biological significance

Chattopadhyay, Tanmay,Mukherjee, Madhupama,Mondal, Arindam,Maiti, Pali,Banerjee, Arpita,Banu, Kazi Sabnam,Bhattacharya, Santanu,Roy, Bappaditya,Chattopadhyay,Mondai, Tapan Kumar,Nethaji, Munirathinam,Zangrando, Ennio,Das, Debasis

, p. 3121 - 3129 (2010)

A new dinuclear nickel(ll) complex, [Ni2(LH2)(H 2O)2(OH)(NO3)](NO3)3 (1), of an "end-off" compartmental ligand 2,6-bis(N-ethylpiperazine- iminomethyl)-4-methyl-phenolato, has been synthesized and structurally characterized. The X-ray single crystal structure analysis shows that the piperazine moieties assume the expected chair conformation and are protonated. The complex 1 exhibits versatile catalytic activities of biological significance, viz. catecholase, phosphatase, and DNA cleavage activities, etc. The catecholase activity of the complex observed is very dependent on the nature of the solvent. In acetonitrile medium, the complex is inactive to exhibit catecholase activity. On the other hand, in methanol, it catalyzes not only the oxidation of 3,5-ditert-buty !catechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very difficult to oxidize, under aerobic conditions. UV-vis spectroscopic investigation shows that TCC oxidation proceeds through the formation of an intermediate. The intermediate has been characterized by an electron spray ionizaton-mass spectrometry study, which suggests a bidentate rather than a monodentate mode of TCC coordination in that intermediate, and this proposition have been verified by density functional theory calculation. The complex also exhibits phosphatase (with substrate p-nitrophenylphosphate) and DNA cleavage activities. The DNA cleavage activity exhibited by complex 1 most probably proceeds through a hydroxyl radical pathway. The bioactivity study suggests the possible applications of complex 1 as a site specific recognition of DNA and/or as an anticancer agent.

Designed four-helix bundle catalysts - The engineering of reactive sites for hydrolysis and transesterification reactions of p-nitrophenyl esters

Baltzer, Lars,Broo, Kerstin S.,Nilsson, Helena,Nilsson, Jonas

, p. 83 - 91 (1999)

Four-helix bundle proteins have been designed that catalyze the hydrolysis and transesterification reactions of p-nitrophenyl esters by a cooperative nucleophilic and general acid mechanism. The catalysts consist of two 42-residue peptides that fold into

Mesoporous zeolites as enzyme carriers: Synthesis, characterization, and application in biocatalysis

Mitchell, Sharon,Pérez-Ramírez, Javier

, p. 28 - 37 (2011)

We study the application of hierarchical ZSM-5 zeolites, combining micropores and intracrystalline mesopores, as carriers for lipase enzymes compared with purely microporous ZSM-5 and mesoporous MCM-41. Strategies to improve enzyme immobilization by modif

Isotope effects and medium effects on sulfuryl transfer reactions

Hoff,Larsen,Hengge

, p. 9338 - 9344 (2001)

Kinetic isotope effects and medium effects have been measured for sulfuryl-transfer reactions of the sulfate ester p-nitrophenyl sulfate (pNPS). The results are compared to those from previous studies of phosphoryl transfer, a reaction with mechanistic si

Organoruthenium(II) compounds with pyridyl benzoxazole/benzthiazole moiety: studies on DNA/protein binding and enzyme mimetic activities

Gomathi, Asaithambi,Vijayan, Paranthaman,Viswanathamurthi, Periasamy,Suresh, Shanmugam,Nandhakumar, Raju,Hashimoto, Takeshi

, p. 1645 - 1666 (2017)

We report herein synthesis and characterization of four new organoruthenium(II) complexes of the type [RuH(CO)(PPh3)2(L1,2)]Cl (1, 3) and [Ru(CO)(Cl)2(AsPh3)(L1,2)] (2, 4) derived from the reaction of [RuHCl(CO)(EPh3)3] (E?=?P or As) with 2-(pyridine-2yl)benzoxazole (L1) and 2-(pyridine-2yl)benzthiazole (L2). Single-crystal X-ray diffraction data of 2 proved octahedral geometry of the complexes with a 1 : 1 ratio between the metal and the coordinated ligands. The binding affinities of 1–4 toward calf-thymus DNA (CT-DNA) and BSA were thoroughly studied by various spectroscopic techniques. Furthermore, the coordination compounds exhibit catecholase-like activities in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone and phosphatase-like activities in the hydrolysis of 4-nitrophenyl phosphate to 4-nitrophenolate ion. The kinetic parameters have been determined using Michaelis–Menten approach. The highest kcat values suggested that coordination compounds exhibit higher rates of catalytic efficacy.

Selective debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate

Zhou, Linna,Wang, Wenjing,Zuo, Li,Yao, Shanyan,Wang, Wei,Duan, Wenhu

, p. 4876 - 4878 (2008)

A new debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate is described. The process proceeds selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, COOMe, aldehyde, ketone, and tosyl.

Iron-catalyzed conversion of unactivated aryl halides to phenols in water

Ren, Yunlai,Cheng, Lin,Tian, Xinzhe,Zhao, Shuang,Wang, Jianji,Hou, Chaodong

, p. 43 - 45 (2010)

Although iron is low-cost and environmentally friendly, there is no report about iron-catalyzed conversion of unactivated aryl halides to phenols. In this Letter, a new method for the present conversion was developed with iron compounds as the catalyst and water as the solvent. The suggested method allowed a series of unactivated aryl bromides and aryl iodides to be converted into the corresponding substituted phenols in moderate to high yields.

Molecular Design of Non-Leloir Furanose-Transferring Enzymes from an α-L-Arabinofuranosidase: A Rationale for the Engineering of Evolved Transglycosylases

Bissaro, Bastien,Durand, Julien,Biarns, Xevi,Planas, Antoni,Monsan, Pierre,O'Donohue, Michael J.,Faur, Rgis

, p. 4598 - 4611 (2015)

The vast biodiversity of glycoside hydrolases (GHs) constitutes a reservoir of readily available carbohydrate-acting enzymes that employ simple substrates and hold the potential to perform highly stereopecific and regioselective glycosynthetic reactions.

Antibody catalyzed modification of amino acids. Efficient hydrolysis of tyrosine benzoate

Benedetti,Berti,Colombatti,Flego,Gardossi,Linda,Peressini

, p. 715 - 716 (2001)

Esterase antibody 522c2, the first example of a catalytic antibody specifically programmed to control the reactivity of functional groups on the side chain of tyrosine, accelerates the hydrolysis of benzoate esters of L-tyrosine and tyrosine-containing dipeptides by a factor of 104 and is moderately active against other benzoate esters.

Parallel Behavior in Kinetic and NMR Effects: Secondary Deuterium Isotope Effects on the Alkaline Hydrolysis of Esters

Matta, Michael S.,Broadway, Dale E.,Stroot, Michele K.

, p. 4916 - 4918 (1987)

β-Deuterium secondary kinetic isotope effects (β-D KIEs) on the alkaline hydrolysis of the p-nitrophenyl esters of acetic, propanoic, butanoic, and pentanoic acids in pH 10.70, 0.20 M carbonate buffer at 25 deg C tend to increase with increasing chain length of the esters up to the pentanoate.The β-D KIEs are respectively 0.975 +/- 0.004, 0.960 +/- 0.002, 0.940 +/- 0.001, and 0.948 +/- 0.004.The activation energies of the esterolyses of the isotopically light esters follow a similar pattern, as do the 13C NMR nuclear shieldings in CDCl3 of the isotopically light parent carboxylic acids (20.9, 27.4, 35.9, and 33.8 (ppm)) and 13C NMR one-bond isotope shifts produced by disubstitution of deuterium for hydrogen at the α-carbons of the acids (0.45, 0.55, 0.60, and 0.59 (ppm)).Correlation of nuclear shieldings and isotope shifts is known from previous work.The possibility is considered that all of the kinetics-based and NMR relationships are linked through the operation of a common ground-state feature of the ester and acid alkyl chains.

Insights into Catalytic Hydrolysis of Organophosphonates at M-OH Sites of Azolate-Based Metal Organic Frameworks

Cao, Ran,Chen, Haoyuan,Farha, Omar K.,Islamoglu, Timur,Kirlikovali, Kent O.,Mian, Mohammad Rasel,Snurr, Randall Q.

, p. 9893 - 9900 (2021)

Organophosphorus nerve agents, a class of extremely toxic chemical warfare agents (CWAs), have remained a threat to humanity because of their continued use against civilian populations. To date, Zr(IV)-based metal organic framework (MOFs) are the most pre

Low ionic liquid concentration in water: A green and simple approach to improve activity and selectivity of lipases

Filice, Marco,Romero, Oscar,Abian, Olga,De Las Rivas, Blanca,Palomo, Jose M.

, p. 49115 - 49122 (2014)

The activity of several commercial and genetically engineered lipases, already immobilized on octyl-Sepharose, in aqueous solutions containing ionic liquids (ILs) in a molar concentration of 0.01 mol L-1 was investigated. Strong variations in t

Influence of Water Structure on Solvolysis in Water-in-Oil Microemulsions

Garcia-Rio, L.,Leis, J. R.,Iglesias, E.

, p. 12318 - 12326 (1995)

The kinetics of solvolysis of diphenylmethyl chloride, 4-nitrophenyl chloroformate, benzoyl chloride, p-anisoyl chloride, and bis(4-nitrophenyl)carbonate in water/AOT/isooctane microemulsions with various water/surfactant mole ratios W (AOT = sodium bis(2-ethylhexyl)sulfosuccinate) were interpreted by using a pseudophase model in which the substrates are assumed to be distributed between the isooctane and interface phases.The W-dependence of the intrinsic rate constants k for solvolysis at the interface depends on the solvolysis mechanism: for SN1 reactions, k decreased with W, which is attributed to decreasing polarity of the interface; contrariwise, SN2 reactions are accelerated by decreasing W, which is attributed to increasing nucleophilicity of interfacial water.

A Dinuclear Dysprosium Complex as an Air-Stable and Recyclable Catalyst: Applications in the Deacetylation of Carbohydrate, Aliphatic, and Aromatic Molecules

Chiu, Ting-Yu,Chin, Wei,Guo, Jiun-Rung,Liang, Chien-Fu,Lin, Po-Heng

, p. 627 - 633 (2019)

Two dinuclear DyIII complexes, [Dy2(hmb)2(OTf)2(H2O)4]?HOTf?2 THF (A?HOTf?2 THF) and [Dy2(hmi)3(H2O)2]?2 HOTf (B?2 HOTf), have been synthesized by the reaction of Dy(OTf)3 and the Schiff-base ligands H2hmb (N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide) or H2hmi ((2-hydroxy-3-methoxyphenyl)methylene isonicotinohydrazine). Disarmed glycosyl trichloroacetimidates can be activated by complex A in the synthesis of 1,2-trans-glycosides with primary and secondary acceptors. This method offers an efficient route to selectively deacetylated monosaccharides and disaccharides in high yields and a green catalyst that can be easily recycled and reused.

Hydrolysis of nitrophenyl esters catalyzed by modified cyclodextrin in water pools in reversed micelles

Nakamura,Sugama

, p. 4682 - 4685 (1984)

-

Parallel synthesis of alkyl methacrylate latexes for use as catalytic media

Miller, Paul D.,Ford, Warren T.

, p. 1151 - 1152 (1998)

Among thirty-two anion exchange latexes prepared by parallel synthesis, those containing 2-ethylhexyl methacrylate units are the most active as catalytic media for alkaline hydrolysis of p-nitrophenyl alkanecarboxylates.

Isolation and characterization of a beta-primeverosidase-like endo-manner beta-glycosidase from Aspergillus fumigatus AP-20.

Yamamoto, Shigeru,Okada, Masamichi,Usui, Taichi,Sakata, Kanzo

, p. 801 - 807 (2002)

A novel beta-glycosidase-producing microorganism was isolated from soil and identified as Aspergillus fumigatus AP-20 based on its taxonomical characteristics. The enzyme was found to be an extracellular protein in the culture of the isolated fungus and w

Kinetic investigation of the phenolysis of phenyl 4-nitrophenyl and phenyl 2,4-dinitrophenyl carbonates

Castro, Enrique A.,Angel, Mauricio,Pavez, Paulina,Santos, Jose G.

, p. 2351 - 2354 (2001)

The reactions of phenyl 4-nitrophenyl carbonate (PDNPC) and phenyl 2,4-dinitrophenyl carbonate (PDNPC) with a homogeneous series of phenoxide anions are subjected to a kinetic investigation in water at 25.0 °C, ionic strength 0.2 mol dm-3 (KCl). Under phenoxide or total phenol excess over the substrate all these reactions obey pseudo first-order kinetics and are first order in phenoxide. The Bronsted-type plots for the nucleophilic rate constants are linear with slopes 0.61 and 0.49 for the phenolysis of PNPC and PDNPC, respectively. The magnitude of these slopes and the absence of curvature in the Brnsted plot at pKa = 7.1 for the PNPC reactions are consistent with concerted mechanisms (one step) for both reaction series. PDNPC is more reactive than PNPC toward phenoxide nucleophiles; this can be explained by the presence of a second nitro group in PDNPC, which (i) leaves its carbonyl carbon more positively charged than that of PNPC, making the former a better electrophile, and (ii) makes 2,4-dinitrophenoxide a better leaving group than 4-nitrophenoxide. The larger nucleophilic rate coefficients found in this work relative to those obtained in the concerted phenolysis of 4-nitrophenyl and 2,4-dinitrophenyl methyl carbonates is explained by a stronger electron withdrawal from PhO compared to MeO. Comparison of the concerted phenolysis of PNPC with the stepwise reactions of quinuclidines with the same substrate indicates that substitution of a quinuclidino group in a zwitterionic tetrahedral intermediate by a phenoxy group greatly destabilises the intermediate.

A strategic approach of enzyme engineering by attribute ranking and enzyme immobilization on zinc oxide nanoparticles to attain thermostability in mesophilic Bacillus subtilis lipase for detergent formulation

Khan, Mohd Faheem,Kundu, Debasree,Hazra, Chinmay,Patra, Sanjukta

, p. 66 - 82 (2019)

The present study envisaged rationalized protein engineering approach to attain thermostability in a mesophilic Bacillus subtilis lipase. Contributing amino acids for thermostability were analyzed from homologous thermophilic-mesophilic protein dataset th

A Mild Strategy for the Preparation of Phenols via the Ligand-Free Copper-Catalyzed O-Arylation of para -Toluenesulfonic Acid

Tan, Bryan Yong-Hao,Teo, Yong-Chua

, p. 1814 - 1819 (2016)

A facile and simple ligand-free copper-catalyzed reaction to synthesize substituted phenols is reported. The reaction presumably proceeds via an O-arylsulfonate intermediate that is hydrolyzed to afford good to excellent yields of up to 88%. This protocol provides an alternative to existing reports which use strong hydroxide salts as the direct hydroxylation partner. Demonstrating a wide substrate scope and functional group tolerance, this protocol can also be applied to inexpensive and commercially available carboxylic acids to yield phenols.

Cellular zwitterionic metabolite analogs simultaneously enhance reaction rate, thermostability, salt tolerance, and substrate specificity of α-glucosidase

Deguchi, Eisuke,Koumoto, Kazuya

, p. 3128 - 3134 (2011)

We investigated the structural effects of metabolite analogs derived from a naturally-occurring zwitterionic metabolite, glycine betaine, on the activity of several hydrolases. The initial velocities of the hydrolases were enhanced by the addition of the

Substrate modulation of the activity of an artificial nanoesterase made of peptide-functionalized gold nanoparticles

Pengo, Paolo,Baltzer, Lars,Pasquato, Lucia,Scrimin, Paolo

, p. 400 - 404 (2007)

Nanozymes with a heart of gold: A functional artificial protein has been prepared by grafting a dodecapeptide onto the surface of gold nanoparticles (see picture). The system catalyzes the hydrolysis of carboxylate esters and features enzyme-like properti

Kinetics and speciation of paraoxon hydrolysis by zinc(II)-azamacrocyclic catalysts

Kennedy, Daniel J.,Mayer, Brian P.,Baker, Sarah E.,Valdez, Carlos A.

, p. 123 - 131 (2015)

Four Zn2+-azamacrocyclic complexes were investigated for their ability to catalyze the hydrolysis of the toxic organophosphate (OP) pesticide diethyl paraoxon. Of the four complexes studied, Zn2+-1,5,9-triazacyclododecane (Zn2+-[12]aneN3) was found to be the most effective catalyst with a pseudo-first order reaction rate of k = 6.08 ± 0.23 × 10-4 min-1. Using 31P nuclear magnetic resonance (NMR) spectroscopy, the two products diethyl phosphate (DEP) and ethyl (4-nitrophenyl) phosphate (E4NPP) were identified for both catalyzed and background hydrolysis of paraoxon. Reaction rate and selectivity for formation of the non-toxic DEP were observed to correlate with catalyst pKa. The rate of formation of toxic E4NPP, however, was independent of both the presence and nature of the catalyst. The potential roles of buffer concentration and product inhibition were also investigated. Background hydrolysis at elevated reaction temperatures (50°C) displayed no preference for DEP over that of E4NPP despite substantial differences between the characteristics (i.e., pKa values) of the two leaving groups (ethoxide vs. 4-nitrophenoxide anions). As with previous observations of these types of metal-catalyzed hydrolyses, we invoke the formation of a trigonal bipyramidal-like transition state involving a Zn-coordinated phosphate bond, with the leaving group at the apical position and the incoming HO- anion approaching from the opposite end. Kinetic rates for catalytic hydrolysis display an overwhelming propensity for DEP formation, and suggest the importance of steric restrictions on transition state structure, namely a concerted arrangement of the azamacrocycle in opposition to the bulky 4-nitrophenoxy group.

Hydrolysis of organophosphate esters: Phosphotriesterase activity of metallo-ss-lactamase and its functional mimics

Tamilselvi,Mugesh, Govindasamy

, p. 8878 - 8886 (2010)

The phosphotriesterase (PTE) activity of a series of binuclear and mononuclear zinc(II) complexes and metallo-β-lactamase (mβl) from Bacillus cereus was studied. The binuclear complex 1, which exhibits good mβl activity, shows poor PTE activity. In contrast, complex 2, a poor mimic of mβl, exhibits much higher activity than 1. The replacement of Cl - ligands by OH- is important for the high PTE activity of complex 2 because this complex does not show any catalytic activi-ty in methanol. The natural enzyme mssl from B. cereus is also found to be an inefficient catalyst in the hydrolysis of phosphotriesters. These observations indicate that the binding of -lactam substrates at the binuclear zinc(II) center is different from that of phosphotriesters. Furthermore, phospho diesters, the products from the hydrolysis of triesters, significantly inhibit the PTE activity of mβl and its functional mimics. Although the mononuclear complexes 3 and 4 exhibited significant mβl activity, these complexes are found to be almost inactive in the hydrolysis of phosphotriesters. These observations indicate that the elimination of phosphodiesters from the reaction site is important for the PTE activity of zinc(II) complexes.

Rationally Designed Double-Shell Dodecahedral Microreactors with Efficient Photoelectron Transfer: N-Doped-C-Encapsulated Ultrafine In2O3 Nanoparticles

Sun, Liming,Li, Rong,Zhan, Wenwen,Wang, Fan,Zhuang, Yuan,Wang, Xiaojun,Han, Xiguang

, p. 3053 - 3060 (2019)

It is desirable but challenging to design efficient micro-/nanoreactors for chemical reactions. In this study, we have fabricated mesoporous double-shelled hollow microreactors composed of N-doped-C-coated ultrafine In2O3 nanoparticles [N-C/In2O3 HD (hollow dodecahedron)] by the thermolysis of a dodecahedral In-based framework in Ar atmosphere. The obtained N-C/In2O3 HD exhibited excellent activity in the photocatalytic oxidative hydroxylation of a series of arylboronic acid substrates. This property can be attributed to its enhanced optical absorption and efficient separation of photo-generated electron–hole pairs, imparted by the unique structure and uniformly coated N-doped C layers. Furthermore, we found O2.? to be the critical active species in the process of photocatalytic oxidative hydroxylation of arylboronic acids, and the formation mechanism of this radical is also proposed. Theoretical calculations further confirmed that the N-doped C layer serves as an electron acceptor and revealed the microscopic charge-carrier migration path through the In2O3/N-doped graphite interfaces. Thus, photo-generated electrons from hybrid states of In2O3, composed of In 5s and 2p orbitals, are transferred into the hybrid states of N-doped graphite, composed of C 2p and N 2p orbitals. The present study may be helpful for understanding and designing carbon-based micro-/nanoreactors for photocatalytic reactions, and may also be useful for investigating related micro-/nanoreactors.

Phenol transformation photosensitised by quinoid compounds

Maurino, Valter,Bedini, Andrea,Borghesi, Daniele,Vione, Davide,Minero, Claudio

, p. 11213 - 11221 (2011)

The phototransformation of phenol in aqueous solution was studied with different quinoid compounds, which are usually detected on atmospheric particulate matter: 2-ethylanthraquinone (EtAQ), benzanthracene-7,12-dione (BAD), 5,12-naphthacenequinone (NQ), 9,10-anthraquinone (AQ), and 2,6-dihydroxyanthraquinone (DAQ). All the studied quinones were able to sensitise the phototransformation of phenol. Under blue-light irradiation the approximated, polychromatic quantum yields for phenol photodegradation were in the order AQ > BAD > EtAQ > NQ > DAQ. Quantum mechanical calculations showed that AQ and DAQ have a very different spin distribution in the triplet state (largely located on the carbonyl oxygen and delocalised over the aromatic ring, respectively) that could account for the difference in reactivity. The spin distribution of EtAQ is similar to that of AQ. Under simulated sunlight, EtAQ induced the highest rate of phenol degradation. Radiation-excited EtAQ would oxidise both ground-state EtAQ and phenol; a kinetic model that excludes the OH radical and singlet oxygen as reactive species is supported by the experimental data. Quinones were also able to oxidise nitrite to nitrogen dioxide, thereby inducing phenol nitration. Such a process is a potential source of nitrogen dioxide and nitrophenols in the atmospheric aerosols. the Owner Societies.

Use of MoO2Cl2(DMF)2 as a precursor for molybdate promoted hydrolysis of phosphoester bonds

Tome, Catia M.,Oliveira, M. Conceicao,Pillinger, Martyn,Goncalves, Isabel S.,Abrantes, Marta

, p. 3901 - 3907 (2013)

Phosphoester bond cleavage of para-nitrophenylphosphate (pNPP), a commonly used model substrate, is accelerated by using the complex MoO2Cl 2(DMF)2 (1) (DMF = dimethylformamide) as a hydrolysis promoting agent, even when c

Lithium pipecolinate as a facile and efficient ligand for copper-catalyzed hydroxylation of aryl halides in water

Jing, Linhai,Wei, Jiangtao,Zhou, Li,Huang, Zhiyong,Li, Zhengkai,Zhou, Xiangge

, p. 4767 - 4769 (2010)

Direct hydroxylation of a wide scope of aryl halides was catalyzed by a combination of CuI and lithium pipecolinate in water with yields up to 92%.

Enzyme shielding in an enzyme-thin and soft organosilica layer

Correro, M. Rita,Moridi, Negar,Schützinger, Hansj?rg,Sykora, Sabine,Ammann, Erik M.,Peters, E. Henrik,Dudal, Yves,Corvini, Philippe F.-X.,Shahgaldian, Patrick

, p. 6285 - 6289 (2016)

The fragile nature of most enzymes is a major hindrance to their use in industrial processes. Herein, we describe a synthetic chemical strategy to produce hybrid organic/inorganic nanobiocatalysts; it exploits the self-assembly of silane building blocks at the surface of enzymes to grow an organosilica layer, of controlled thickness, that fully shields the enzyme. Remarkably, the enzyme triggers a rearrangement of this organosilica layer into a significantly soft structure. We demonstrate that this change in stiffness correlates with the biocatalytic turnover rate, and that the organosilica layer shields the enzyme in a soft environment with a markedly enhanced resistance to denaturing stresses. Important soft skills: Hybrid organic/inorganic nanobiocatalysts were created by the immobilization of enzymes on amino-modified silica nanoparticles and subsequent self-assembly and polycondensation of silane building blocks at the surface of the enzymes. The soft environment of the organosilica layer shielded the enzymes from denaturing stresses; however, the enzymes retained their conformational freedom and thus their catalytic activity (see picture).

Nylon–MOF Composites through Postsynthetic Polymerization

Kalaj, Mark,Denny, Michael S.,Bentz, Kyle C.,Palomba, Joseph M.,Cohen, Seth M.

, p. 2336 - 2340 (2019)

Hybridization of metal–organic frameworks (MOFs) and polymers into composites yields materials that display the exceptional properties of MOFs with the robustness of polymers. However, the realization of MOF–polymer composites requires efficient dispersion and interactions of MOF particles with polymer matrices, which remains a significant challenge. Herein, we report a simple, scalable, bench-top approach to covalently tethered nylon–MOF polymer composite materials through an interfacial polymerization technique. The copolymerization of a modified UiO-66-NH2 MOF with a growing polyamide fiber (PA-66) during an interfacial polymerization gave hybrid materials with up to around 29 weight percent MOF. The covalent hybrid material demonstrated nearly an order of magnitude higher catalytic activity for the breakdown of a chemical warfare simulant (dimethyl-4-nitrophenyl phosphate, DMNP) compared to MOFs that are non-covalently, physically entrapped in nylon, thus highlighting the importance of MOF–polymer hybridization.

Mesoporous Core-Shell Nanostructures Bridging Metal and Biocatalyst for Highly Efficient Cascade Reactions

Gao, Jing,Gao, Shiqi,Jiang, Yanjun,Liu, Yunting,Ma, Li,Wang, Zihan

, p. 1375 - 1380 (2020)

Mesoporous core-shell structured nanocatalysts with a PdPt bimetallic core and enzyme-immobilized polydopamine (PDA) shell were designed, in which the PDA shell worked as a barrier to position the bimetallic core and enzyme in separated locations. The accessible mesoporous structures of both the core and shell significantly facilitate mass transfer and catalyst utilization, improving the synergistic catalytic abilities in cascade reactions. The obtained bifunctional nanocatalysts enabled efficient two-step one-pot cascade reactions of different types: dynamic kinetic resolution of primary amines in organic solvent with high yield and enantioselectivity (up to 99% yield and 98% ee) and degradation of organophosphate nerve agent in aqueous solution with high rate constant and turnover frequency number values (0.8 min-1 and 20 min-1, respectively).

The catalytic serine of meta-cleavage product hydrolases is activated differently for C-O bond cleavage than for C-C bond cleavage

Ruzzini, Antonio C.,Horsman, Geoff P.,Eltis, Lindsay D.

, p. 5831 - 5840 (2012)

meta-Cleavage product (MCP) hydrolases catalyze C-C bond fission in the aerobic catabolism of aromatic compounds by bacteria. These enzymes utilize a Ser-His-Asp triad to catalyze hydrolysis via an acyl-enzyme intermediate. BphD, which catalyzes the hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) in biphenyl degradation, catalyzed the hydrolysis of an ester analogue, p-nitrophenyl benzoate (pNPB), with a kcat value (6.3 ± 0.5 s-1) similar to that of HOPDA (6.5 ± 0.5 s-1). Consistent with the breakdown of a shared intermediate, product analyses revealed that BphD catalyzed the methanolysis of both HOPDA and pNPB, partitioning the products to benzoic acid and methyl benzoate in similar ratios. Turnover of HOPDA was accelerated up to 4-fold in the presence of short, primary alcohols (methanol > ethanol > n-propanol), suggesting that deacylation is rate-limiting during catalysis. In the steady-state hydrolysis of HOPDA, kcat/Km values were independent of methanol concentration, while both kcat and Km values increased with methanol concentration. This result was consistent with a simple model of nucleophilic catalysis. Although the enzyme could not be saturated with pNPB at methanol concentrations of >250 mM, kobs values from the steady-state turnover of pNPB at low methanol concentrations were also consistent with a nucleophilic mechanism of catalysis. Finally, transient-state kinetic analysis of pNPB hydrolysis by BphD variants established that substitution of the catalytic His reduced the rate of acylation by more than 3 orders of magnitude. This suggests that for pNPB hydrolysis, the serine nucleophile is activated by the His-Asp dyad. In contrast, rapid acylation of the H265Q variant during C-C bond cleavage suggests that the serinate forms via a substrate-assisted mechanism. Overall, the data indicate that ester hydrolysis proceeds via the same acyl-enzyme intermediate as that of the physiological substrate but that the serine nucleophile is activated via a different mechanism.

The mechanism by which 4-hydroxy-2,2,6,6-tetramethylpiperidene-1-oxyl (tempol) diverts peroxynitrite decomposition from nitrating to nitrosating species

Bonini, Marcelo G.,Mason, Ronald P.,Augusto, Ohara

, p. 506 - 511 (2002)

Tempol is a stable nitroxide radical that has been shown to protect laboratory animals from the injury associated with conditions of oxidative and nitrosoactive stress. Tempol's protective mechanisms against reactive oxygen species have been extensively studied, but its interactions with reactive nitrogen species remain little explored. Recently, it has been shown that tempol is a potent inhibitor of peroxynitrite-mediated phenol nitration while it increases phenol nitrosation by a complex mechanism [Carrol et al. (2000) Chem. Res. Toxicol. 13, 294]. To obtain further mechanistic insights, we reexamined the interaction of peroxynitrite with tempol in the absence and presence of carbon dioxide. Stopped-flow kinetic studies confirmed that tempol does not react directly with peroxynitrite but levels off the amount of oxygen (monitored with an oxygen electrode) and nitrite (monitored by chemiluminescence) produced from peroxynitrite in the presence and absence of carbon dioxide to about 30% and 70% of the initial oxidant concentration at pH 5.4, 6.4, and 7.4. Tempol inhibited phenol nitration while increasing the amounts of 4-nitrosophenol, that attained yields close to 30% of the peroxynitrite in the presence of carbon dioxide at pH 7.4. Fast-flow EPR experiments showed detectable changes in the instantaneous tempol concentration (maximum of 15%) only in the presence of carbon dioxide. Under these conditions, the instantaneous concentration of the carbonate radical anion was reduced by tempol in a concentration-dependent manner. The results indicate that tempol is oxidized by peroxynitrite-derived radicals (·OH and CO3·-, in the absence and presence of carbon dioxide, respectively) to the oxoammonium cation which, in turn, is reduced back to tempol while oxidizing peroxynitrite to oxygen and nitric oxide. The latter reacts rapidly with peroxynitrite-derived nitrogen dioxide to produce the nitrosating species, dinitrogen trioxide. Overall, the results support a role for peroxynitrite and its derived radicals in the tissue pathology associated with inflammatory conditions.

Solvent effects on reactions of hydroxide and oximate ions with phosphorus(V) esters

Bunton, Clifford A.,Gillitt, Nicholas D.,Kumar, Anurag

, p. 221 - 228 (1997)

Second-order rate constants of reactions of OH-, 2,3-butanedionemonooximate and 2-hydroxybenzaldoximate ions with aryl phosphate, phosphinate and thioarylphosphinate esters go through minima with decreasing water content of aqueous acetonitrile, tert-butyl alcohol and N-methyl-2-pyrrolidone. For reactions in H2O-MeCN the solvent effects are analyzed in terms of activity coefficients of the anionic nucleophiles and transition states. In the drier solvents partial desolvation of the nucleophiles increases rates. Nucleophilicities of several oximates and inorganic anions are compared in water.

Inhibition of Yersinia protein tyrosine phosphatase by phosphonate derivatives of calixarenes

Vovk, Andriy I.,Kononets, Lyudmyla A.,Tanchuk, Vsevolod Yu.,Cherenok, Sergiy O.,Drapailo, Andriy B.,Kalchenko, Vitaly I.,Kukhar, Valery P.

, p. 483 - 487 (2010)

Inhibition of Yersinia protein tyrosine phosphatase by calix[4]arene mono-, bis-, and tetrakis(methylenebisphosphonic) acids as well as calix[4]arene and thiacalix[4]arene tetrakis(methylphosphonic) acids have been investigated. The kinetic studies reveal

Motif-guided identification of a glycoside hydrolase family 1 α-L-arabinofuranosidase in bifidobacterium adolescentis

Suzuki, Hirokazu,Murakami, Ayano,Yoshida, Ken-Ichi

, p. 1709 - 1714 (2013)

Members of glycoside hydrolase family 1 (GH1) cleave glycosidic linkages with a variety of physiological roles. Here we report a unique GH1 member encoded in the genome of Bifidobacterium adolescentis ATCC 15703. This enzyme, BAD0156, was identified from

Functional characterization of salt-tolerant microbial esterase WDEst17 and its use in the generation of optically pure ethyl (R)-3-hydroxybutyrate

Wang, Yilong,Xu, Yongkai,Zhang, Yun,Sun, Aijun,Hu, Yunfeng

, p. 769 - 776 (2018)

The two enantiomers of ethyl 3-hydroxybutyrate are important intermediates for the synthesis of a great variety of valuable chiral drugs. The preparation of chiral drug intermediates through kinetic resolution reactions catalyzed by esterases/lipases has been demonstrated to be an efficient and environmentally friendly method. We previously functionally characterized microbial esterase PHE21 and used PHE21 as a biocatalyst to generate optically pure ethyl (S)-3-hydroxybutyrate. Herein, we also functionally characterized one novel salt-tolerant microbial esterase WDEst17 from the genome of Dactylosporangium aurantiacum subsp. Hamdenensis NRRL 18085. Esterase WDEst17 was further developed as an efficient biocatalyst to generate (R)-3-hydroxybutyrate, an important chiral drug intermediate, with the enantiomeric excess being 99% and the conversion rate being 65.05%, respectively, after process optimization. Notably, the enantio-selectivity of esterase WDEst17 was opposite than that of esterase PHE21. The identification of esterases WDEst17 and PHE21 through genome mining of microorganisms provides useful biocatalysts for the preparation of valuable chiral drug intermediates.

Guanidine-based polymer brushes grafted onto silica nanoparticles as efficient artificial phosphodiesterases

Savelli, Claudia,Salvio, Riccardo

, p. 5856 - 5863 (2015)

Polymer brushes grafted to the surface of silica nanoparticles were fabricated by atom-transfer radical polymerization (ATRP) and investigated as catalysts in the cleavage of phosphodiesters. The surfaces of silica nanoparticles were functionalized with an ATRP initiator. Surface-initiated ATRP reactions, in varying proportions, of a methacrylate moiety functionalized with a phenylguanidine moiety and an inert hydrophilic methacrylate species afforded hybrid nanoparticles that were characterized with potentiometric titrations, thermogravimetric analysis, and SEM. The activity of the hybrid nanoparticles was tested in the transesterification of the RNA model compound 2-hydroxypropyl para-nitrophenylphosphate (HPNP) and diribonucleoside monophosphates. A high catalytic efficiency and a remarkable effective molarity, thus overcoming the effective molarities previously observed for comparable systems, indicate the existence of an effective cooperation of the guanidine/guanidinium units and a high level of preorganization in the nanostructure. The investigated system also exhibits a marked and unprecedented selectivity for the diribonucleoside sequence CpA. The results presented open up the way for a novel and straightforward strategy for the preparation of supramolecular catalysts.

β-D-GLUCOSIDASE-CATALYSED TRANSFER OF THE GLYCOSYL GROUP FROM ARYL β-D-GLUCO- AND β-D-XYLO-PYRANOSIDES TO PHENOLS

Aerts, Guido M.,Opstal, Omer Van,Bruyne, Clement K. De

, p. 221 - 234 (1982)

The effect of phenols on the hydrolysis of substituted phenyl β-D-gluco- and β-D-xylo-pyranosides by β-D-glucosidase from Stachybotrys atra has been investigated.Depending on the glycon part of the substrate and on the phenol substituent, the hydrolysis is either inhibited or activated.With aryl β-D-glucopyranosides, such transfer does not occur when phenols are used as acceptors, but it does occur with anilines.A two-steps mechanism, in which the first step is partially reversible, is proposed to explain these observations.A qualitative analysis of the various factors determing the overall effect of the phenol is given.

Participation of an Extended p-Oxo Ketene Intermediate in the Dissociative Alkaline Hydrolysis of Aryl 4-Hydroxycinnamates

Cevasco, Giorgio,Thea, Sergio

, p. 6274 - 6278 (1994)

The alkaline hydrolysis of 4-hydroxycinnamate esters of acidic phenols follows an E1cB mechanism and involves the participation of an "extended" p-oxo ketene intermediate.The apparent bimolecular rate constant (kaKa/Kw) for the hydrolysis of the 2,4-dinitrophenyl ester is some 2500-fold larger than that determined from the Hammett relationship for the BAc2 alkaline hydrolysis of substituted 2,4-dinitrophenyl cinnamates.The positive value of entropy of activation for the hydrolysis of 2,4-dinitrophenyl 4'-hydroxycinnamate and trapping experiments with nitrogen nucleophiles are consistent with the dissociative pathway.A change from a E1cB to a BAc2 mechanism is expected for esters with leaving groups having pKa higher than ca. 6.7.The higher E1cB reactivity of 2,4-dinitrophenyl 4'-hydroxycinnamate compared to that of the corresponding 4'-hydroxybenzoate is due to the vinylene group that further favors the dissociative route, probably increasing the stability of the unsaturated intermediate.

Evolution of metal complex-catalysts by dynamic templating with transition state analogs

Matsumoto, Masaomi,Estes, Deven,Nicholas, Kenneth M.

, p. 1847 - 1852 (2010)

The elicitation of hydrolytic catalysts from a dynamic library of imine-zinc(II) complexes (and their precursor aldehydes and amines) via templating with pro-transition state analogs (pro-TSA) is described. pro-TSA (2-pyridyl)phosphonate 2 amplifies a ben

A Simple Method for the Selective Deprotection of p-Methoxybenzyl Ethers by Cerium(III) Chloride Heptahydrate and Sodium Iodide

Cappa, Anna,Marcantoni, Enrico,Torregiani, Elisabetta,Bartoli, Giuseppe,Bellucci, Maria Cristina,Bosco, Marcella,Sambri, Letizia

, p. 5696 - 5699 (1999)

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Isoenzymes of pig-liver esterase reveal striking differences in enantioselectivities

Hummel, Anke,Bruesehaber, Elke,Boettcher, Dominique,Trauthwein, Harald,Doderer, Kai,Bornscheuer, Uwe T.

, p. 8492 - 8494 (2007)

(Graph Presented) An esterase toolbox: A set of isoenzymes of pig liver esterases (PLE) is identified, cloned, and overexpressed in E. coli. They show striking differences in enantioselectivity and enantiopreference in the kinetic resolution of acetates o

Characterization of alkaline phosphatase PhoK from Sphingomonas sp. BSAR-1 for phosphate monoester synthesis and hydrolysis

Lukesch, Michael,Tasnádi, Gábor,Ditrich, Klaus,Hall, Mélanie,Faber, Kurt

, (2020)

The biocatalytic activity of a so far underexploited alkaline phosphatase, PhoK from Sphingomonas sp. BSAR-1, was extensively studied in transphosphorylation and hydrolysis reactions. The use of high-energy phosphate donors and oligophosphates as suitable

Highly efficient phosphate diester transesterification by a calix[4]arene-based dinuclear zinc(II) catalyst

Molenveld,Kapsabelis,Engbersen,Reinhoudt

, p. 2948 - 2949 (1997)

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Influence of hydrogen bonding in the activation of nucleophiles: PhSH- (catalytic) KF in N-methyl-2-pyrrolidone as an efficient protocol for selective cleavage of alkyl/aryl esters and aryl alkyl ethers under nonhydrolytic and neutral conditions

Chakraborti, Asit K.,Sharma, Lalima,Nayak, Mrinal K.

, p. 2541 - 2547 (2002)

The nucleophilicity of arenethiols can be augmented via hydrogen bonding with 'naked' halide anion. The activity of the halide anions follow the order F- ?Cl- ~ Br- ~ I- and is dependent on the countercation (Bu4N ~ Cs ~ K > Na ?Li). The solvent plays an important role in nucleophilic activation as well as regeneration of the effective nucleophile (e.g. ArS-) and those with high dielectric constant, high molecular polarizability, high donor number (DN), and low acceptor number (AN) are the most effective. Selective deprotection of alkyl/aryl esters and aryl alkyl ethers can be achieved under nonhydrolytic and neutral conditions by the treatment with thiophenol in 1-methyl-2-pyrrolidone (NMP) in the presence of a catalytic amount of KF. Aryl esters are selectively deprotected in the presence of alkyl esters and alkyl methyl ethers during intramolecular competitions.

Rates of Reaction in the p-Nitrophemol-Triethylamine System in Acetonitrile

Marshall, David B.,Strohbusch, Frank,Eyring, Edward M.

, p. 2270 - 2273 (1981)

The rate constants of proton transfer between p-nitrophenol (AH) and triethylamine (B) in acetonitrile (ionic strength μ1.3E-4 M, 25.0 deg C) were measured by the electric field jump relaxation method with spectrophotometric detection.This acid-base syst

Colorimetric Determination of Sulfate via an Enzyme Cascade for High-Throughput Detection of Sulfatase Activity

Ortiz-Tena, Jose G.,Rühmann, Broder,Sieber, Volker

, p. 2526 - 2533 (2018)

High-throughput screening (HTS) methods have become decisive for the discovery and development of new biocatalysts and their application in numerous fields. Sulfatases, a broad class of biocatalysts that hydrolyze sulfate esters, are involved in diverse r

Rapid photocatalytic degradation of nitrobenzene under the simultaneous illumination of UV and microwave radiation fields with a TiO2 ball catalyst

Jeong, Sangmin,Lee, Heon,Park, Hyunwoong,Jeon, Ki-Joon,Park, Young-Kwon,Jung, Sang-Chul

, p. 65 - 72 (2018)

To use the microwave/ML/TiO2 hybrid system as an advanced treatment of nitrobenzene (NB), a series of experiments were performed to examine the effects of microwave irradiation and auxiliary oxidants. The degradation of NB was carried out using different combinations of five-unit treatment techniques. The NB degradation rate increased with increasing microwave intensity. The circulation fluid velocity, concentration of H2O2, and the rate of O2 gas injection showed the highest rate of degradation under optimal conditions. A significant synergistic effect was observed when H2O2 addition was combined with the microwave/ML/TiO2 hybrid process.

A facile, selective KF/Al2O3 mediated method for the deprotection of aryl silyl ethers and preparation of aryl SEM ethers

Blass, Benjamin E.,Harris, Cheryl L.,Portlock, David E.

, p. 1611 - 1613 (2001)

A selective, solvent dependent KF/Al2O3 mediated method for the cleavage of aryl silyl ethers and the preparation of SEM aryl ethers is reported.

Promotion of phosphoester hydrolysis by MoO2Cl2L (L = bipyridine derivatives, H2O, no ligand), MoO2(CH 3)2L (L = bipyridine derivatives) and related inorganic-organic hybrids in aqueous med

Gomes, Ana C.,Pillinger, Martyn,Nunes, Patrique,Gon?alves, Isabel S.,Abrantes, Marta

, p. 42 - 47 (2014)

The compounds MoO2Cl2L (L = 2,2′-bipyridine (bipy) (1); 4,4′-di-tert-butyl-2,2′-bipyridine (di- tBu-bipy) (2)), [MoO2Cl2(H2O) 2]·(diglyme)2 (3), MoO2Cl

-

Eberhardt

, p. 1913,1914-1916 (1975)

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Phosphate Ester Hydrolysis Facilitated by Mineral Phases

Baldwin, Darren S.,Beattie, James K.,Coleman, Lynette M.,Jones, David R.

, p. 1706 - 1709 (1995)

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Reactivity of benzohydrazide derivatives towards acetylation reaction. Experimental and theoretical studies

Campodónico, Paola R.,Aliaga, Margarita E.,Santos, José G.,Castro, Enrique A.,Contreras, Renato

, p. 86 - 89 (2010)

We herein report an experimental and theoretical study on the acetylation reaction of benzohydrazide derivatives towards p-nitrophenyl acetate (NPA). The kinetic data are consistent with a stepwise mechanism with the nucleophilic attack as the rate determ

Exclusive Free Radical Dediazoniation of Benzenediazonium Ions by β-Cyclodextrin

Fukunishi, Koushi,Kazumura, Hideki,Yamanaka, Hiroki,Nomura, Mototeru,Kojo, Shosuke

, p. 799 - 800 (1982)

Dediazoniation of substituted benzenediazonium ions is accelerated by β-cyclodextrin and proceeds through a radical pathway, forming X-C6H4-H whatever the substituent (X) or the atmosphere (N2 or O2).

Thermal Decomposition of Peroxydisulfate in Aqueous Solutions of Benzene-Nitrobenzene-Benzonitrile Mixtures. Formation of OH Radicals from Benzene Radical Cations and Water at Room Temperature

Eberhardt, Manfred K.,Martinez, Gines A.,Rivera, Juana I.,Fuentes-Aponte, Anselmo

, p. 7069 - 7073 (1982)

The thermal decomposition of Na2S2O8 in aqueous solutions of benzene and nitrobenzene at 80 deg C, 40 deg C, and room temperature gives phenol, biphenyl, and o- and p-nitrophenol.In the absence of benzene no nitrophenols were formed under otherwise identical conditions.We have previously suggested a dissociation of the intermediate hydroxycyclohexadienyl radicals to OH radical and benzene.On the basis of kinetics of the reactions involved and the Ea and A values for the dissociation of the hydroxycyclohexadienyl radicals, we have estimated that under our reaction conditions even at room temperature a considerable fraction of hydroxycyclohexadienyl radicals dissociates to OH radicals and benzene.In addition to nitrobenzene we have used benzonitrile as a scavenger for OH radicals.The results of competition experiments between benzene, nitrobenzene, and benzonitrile are consistent with the formation of free OH radicals.

New functional aspects of the atypical protein tyrosine phosphatase VHZ

Kuznetsov, Vyacheslav I.,Hengge, Alvan C.

, p. 8012 - 8025 (2013)

LDP3 (VHZ) is the smallest classical protein tyrosine phosphatase (PTP) known to date and was originally misclassified as an atypical dual-specificity phosphatase. Kinetic isotope effects with steady-state and pre-steady-state kinetics of VHZ and mutants

Surface-mediated highly efficient regioselective nitration of aromatic compounds by bismuth nitrate

Samajdar,Becker,Banik

, p. 8017 - 8020 (2000)

Montmorillonite impregnated with bismuth nitrate was found to be an excellent reagent for aromatic nitration in high yield. (C) 2000 Elsevier Science Ltd.

A very simple copper-catalyzed synthesis of phenols employing hydroxide salts

Tlili, Anis,Xia, Ning,Monnier, Florian,Taillefer, Marc

, p. 8725 - 8728 (2009)

Cheap and cheerful: The direct coppercatalyzed hydroxylation of activated and unactivated aryl iodides or bromides has been achieved using metal hydroxide salts (MOH). Selective hydroxylation in a H20/ co-solvent system avoids formation of the related biaryl ether by-product and the low cost of the copper catalytic system makes this method very competitive.

Remarkable enhancement of the hydrolyses of phosphoesters by dinuclear centers: Streptomyces aminopeptidase as a 'natural model system'

Ercan,Hyun Ik Park,Ming

, p. 2501 - 2502 (2000)

The transition-state analogues bis(p-nitrophenyl)phosphate and p-nitrophenyl phenylphosphonate for peptide hydrolysis are shown to be very effectively hydrolyzed by Streptomyces dinuclear aminopeptidase and its Co2+, Ni2+, Mn2+

TiO2-SiO2 mixed oxide supported MoO3 catalyst: Physicochemical characterization and activities in nitration of phenol

Kemdeo,Sapkal,Chaudhari

, p. 70 - 77 (2010)

12 wt% MoO3/TiO2-SiO2 solid acid catalyst was prepared and calcined at various temperatures. The calcined catalyst was characterized by XRD, FT-IR, BET, SEM, NH3-TPD and pyridine adsorbed FT-IR methods. The effect of calcination temperature on activity of catalyst was studied by choosing liquid phase nitration of phenol as a model reaction. For the same reaction effect of various solvents, effect of reaction time and reusability of the catalyst was also studied. Catalyst calcined at 500 °C temperature showed highest phenol conversion whereas greater o-nitrophenol selectivity is claimed over catalyst calcined at 700 °C. It was observed that high phenol conversion co-relates with the presence of greater number of strong Bro?nsted acid sites over the catalyst surface whereas the selectivity of o-nitrophenol is related to the pore size of the catalysts. No use of sulfuric acid along with the nitric acid used in its diluted form in the reaction makes the process safe and environmentally friendly.

Supramolecular oxidation of anilines using hydrogen peroxide as stoichiometric oxidant

Marinescu, Lavinia,Molbach, Merete,Rousseau, Cyril,Bols, Mikael

, p. 17578 - 17579 (2005)

6A,6D-Di-O-(propan-2-on-1,3-diyl) α-cyclodextrin-6A,6D-dicarboxylate (2α) and 6A,6D-di-O-(propan-2-on-1,3-diyl) β-cyclodextrin-6A,6D-dicarboxylate (2β) were found to catalyze the oxidation of aromatic amines in the presence of hydrogen peroxide. The products were the corresponding nitro compounds or in some cases azo-, azoxy-, or other dimerization products. The catalysis was found to follow enzyme kinetics giving a rate increase (kcat/kuncat) of up to 1100 in the best case. Copyright

Target-specific control of lymphoid-specific protein tyrosine phosphatase (Lyp) activity

Walton, Zandra E.,Bishop, Anthony C.

, p. 4884 - 4891 (2010)

Lymphoid-specific protein tyrosine phosphatase (Lyp), a member of the protein tyrosine phosphatase (PTP) superfamily of enzymes, is an important mediator of human-leukocyte signaling. Lyp has also emerged as a potential anti-autoimmune therapeutic target,

Metal ion promoted transesterifications of carboxylate esters. A structure/activity study of the efficacy of Zn2+ and La3+ to catalyze the methanolysis of some aryl and aliphatic esters

Neverov, Alexei A.,Sunderland,Brown, R. Stan

, p. 65 - 72 (2005)

The methanolysis of various aryl and aliphatic carboxylate esters promoted by methoxide, 1,5,9-triazacyclododecane: Zn2+(-OCH 3) and La3+(-OCH3), were studied and the derived rate constants (kOCH3, kcat 3:Zn(OCH3) and kcatLa(OCH3)) correlated in various ways. The metal ion catalyzed reactions are very much faster than the background reactions in some cases reaching up to 7 × 106-fold acceleration when present at concentrations of 5 mmol dm-3. The data for both metals exhibit non-linear Bronsted correlations with the pK a of the leaving group which are analyzed in terms of a change in rate limiting step from formation to breakdown of a metal-coordinated tetrahedral intermediate as the pKa increases above values of ~14.7. Plots of the log kOCH3 reaction vs. the log k cat, values for each metal ion indicate low sensitivity for aryl esters and a higher sensitivity for the aliphatic esters. A mechanistic rationale for the observations is presented.

Green Photoorganocatalytic Synthesis of Phenols from Arylboronic Acids

Sideri, Ioanna K.,Voutyritsa, Errika,Kokotos, Christoforos G.

, p. 1324 - 1328 (2018)

A green and cheap protocol for the photocatalytic hydroxylation of arylboronic acids is presented. 2,2-Dimethoxy-2-phenylacetophenone proved to be the best photoinitiator, among a range of organocatalysts in promoting this reaction. This photocatalytic protocol can be expanded into a wide substrate scope of aromatic boronic acids bearing various functional groups, leading to the corresponding phenols in good to high yields under mild reaction conditions, which include water as solvent, light irradiation provided from standard light-bulbs at room temperature.

The molecular details of WPD-loop movement differ in the protein-tyrosine phosphatases YopH and PTP1B

Brandao, Tiago A.S.,Johnson, Sean J.,Hengge, Alvan C.

, p. 53 - 59 (2012)

The movement of a conserved protein loop (the WPD-loop) is important in catalysis by protein tyrosine phosphatases (PTPs). Using kinetics, isotope effects, and X-ray crystallography, the different effects arising from mutation of the conserved tryptophan

Thermosensitive imidazole-containing polymers as catalysts in hydrolytic decomposition of p-nitrophenyl acetate

Okhapkin, Ivan M.,Bronstein, Lyudmila M.,Makhaeva, Elena E.,Matveeva, Valentina G.,Sulman, Esther M.,Sulman, Mikhail G.,Khokhlov, Alexei R.

, p. 7879 - 7883 (2004)

Poly(N-vinylcaprolactam-co-1-vinylimidazole) (PVCL-Vim) and poly(N-isopropylacrylamide-co-1-vinylimidazole) (PNIPA-Vim) are thermosensitive in water and water-2-propanol solutions. These copolymers are soluble at room temperature; however, they undergo ph

Kinetic and spectroscopic characterization of intermediates and component interactions in reactions of methane monooxygenase from Methylococcus capsulatus (Bath)

Liu, Katherine E.,Valentine, Ann M.,Wang, Danli,Huynh, Boi Hanh,Edmondson, Dale E.,Salifoglou, Athanasios,Lippard, Stephen J.

, p. 10174 - 10185 (1995)

We describe mechanistic studies of the soluble methane monooxygenase (sMMO) enzyme system from Methylococcus capsulatus (Bath). Interactions among the three sMMO components, the hydroxylase (H), reductase (R), and protein B (B), were investigated by monit

α-galactosidase/sucrose kinase (AgaSK), a novel bifunctional enzyme from the human microbiome coupling galactosidase and kinase activities

Bruel, Laetitia,Sulzenbacher, Gerlind,Tison, Marine Cervera,Pujol, Ange,Nicoletti, Cendrine,Perrier, Josette,Galinier, Anne,Ropartz, David,Fons, Michel,Pompeo, Frederique,Giardina, Thierry

, p. 40814 - 40823 (2011)

α-Galactosides are non-digestible carbohydrates widely distributed in plants. They are a potential source of energy in our daily food, and their assimilation by microbiota may play a role in obesity. In the intestinal tract, they are degraded by microbial glycosidases, which are often modular enzymes with catalytic domains linked to carbohydrate-binding modules. Here we introduce a bifunctional enzyme from the human intestinal bacterium Ruminococcus gnavus E1, α-galactosidase/sucrose kinase (AgaSK). Sequence analysis showed that AgaSK is composed of two domains: one closely related to α-galactosidases from glycoside hydrolase family GH36 and the other containing a nucleotide-binding motif. Its biochemical characterization showed that AgaSK is able to hydrolyze melibiose and raffinose to galactose and either glucose or sucrose, respectively, and to specifically phosphorylate sucrose on the C6 position of glucose in the presence of ATP. The production of sucrose-6-P directly from raffinose points toward a glycolytic pathway in bacteria, not described so far. The crystal structures of the galactosidase domain in the apo form and in complex with the product shed light onto the reaction and substrate recognition mechanisms and highlight an oligomeric state necessary for efficient substrate binding and suggesting a cross-talk between the galactose and kinase domains.

Tetraacuo-bis-(N,N-dimethylacetamide-O)magnesium(II) chloride dihydrate. An option to improve magnesium effect on phosphatase stimulation and albumin binding

Echeverría, Gustavo A.,Ferrer, Evelina G.,Franca, Carlos A.,Martini, Nancy,Parente, Juliana E.,Piro, Oscar E.,Restrepo-Guerrero, Gonzalo,Williams, Patricia A. M.

, (2021)

Magnesium compounds became relevant since the discovery that this element is essential and its deficiency causes several diseases. From these findings, magnesium supplementation became a pharmacologically important issue that prompted the search for new d

Water-soluble cyclopalladated aryl oxime: A potent 'green' catalyst

Bezsoudnova, Ekaterina Yu.,Ryabov, Alexander D.

, p. 38 - 42 (2001)

Orthopalladated aryl oxime with a 15-crown-5 motif is prepared in a 72% yield by the exchange of cyclopalladated ligands from oxime of 4′-acetylbenzo-15-crown-5 and orthometalated N,N-dimethylbenzylamine, [Pd(o-C6H4CH2NMe

Transesterification of phosphotriester paraoxon catalyzed by ZnCl 2 supported on silica gel

Kady, Ismail O.

, p. 744 - 745 (2008)

ZnCl2 supported on silica gel has shown to be an effective catalyst for transesterification of the organophosphate insecticide, paraoxon, in the presence of 2-phenylethanol. The kinetics of the reaction in acetonitrile was studied. Formation of

The kinetics of p-nitrophenyl-β-d-cellobioside hydrolysis and transglycosylation by Thermobifida fusca Cel5Acd

Dingee, John W.,Anton, A. Brad

, p. 2507 - 2515 (2010)

The hydrolysis of p-nitrophenyl-β-1,4-cellobioside (pNP-G2) by the catalytic domain of the retaining-family 5-2 endocellulase Cel5A from Thermobifida fusca (Cel5Acd) was studied. The dominant reaction pathway involves hydrolysis of the aglyconic bond, pro

Functional genomic analysis of Arabidopsis thaliana glycoside hydrolase family 35

Ahn, Young Ock,Zheng, Meiying,Bevan, David R.,Esen, Asim,Shiu, Shin-Han,Benson, Jonas,Peng, Hsiao-Ping,Miller, Joseph T.,Cheng, Chi-Lien,Poulton, Jonathan E.,Shih, Ming-Che

, p. 1510 - 1520 (2007)

Catalysing the hydrolysis of terminal β-galactosyl residues from carbohydrates, galactolipids, and glycoproteins, glycoside hydrolase family 35 (β-galactosidases; BGALs) are widely distributed in plants and believed to play many key roles, including modification of cell wall components. Completion of the Arabidopsis thaliana genome sequencing project has, for the first time, allowed an examination of the total number, gene structure, and evolutionary patterns of all Family 35 members in a representative (model) angiosperm. Reiterative database searches established a multigene family of 17 members (designated BGAL1-BGAL17). Using these genes as query sequences, BLAST and Hidden Markov Model searches identified BGAL genes among 22 other eukaryotes, whose genomic sequences are known. The Arabidopsis (n = 17) and rice (n = 15) BGAL families were much larger than those of Chlamydomonas, fungi, and animals (n = 0-4), and a lineage-specific expansion of BGAL genes apparently occurred after divergence of the Arabidopsis and rice lineages. All plant BGAL genes, with the exception of Arabidopsis BGAL17 and rice Os 9633.m04334, form a monophyletic group. Arabidopsis BGAL expression levels are much higher in mature leaves, roots, flowers, and siliques but are lower in young seedlings. BGAL8, BGAL11, BGAL13, BGAL14, and BGAL16 are expressed only in flowers. Catalytically active BGAL4 was produced in the E. coli and baculoviral expression systems, purified to electrophoretic homogeneity, and partially characterized. The purified enzyme hydrolyzed p- and o-nitrophenyl-β-d-galactosides. It also cleaved β-(1,3)-, β-(1,4)-, and β-(1,6)-linked galactobiosides and galactotriosides, showing a marked preference for β-(1,3)- and β-(1,4)-linkages.

OXIDATION OF TRIS(p-NITROPHENYL)METHANE BY OXYGEN IN THE PRESENCE OF KOH IN DIMETHOXYETHANE

Beletskaya, I. P.,Grinfel'd, A. A.,Artamkina, G. A.

, p. 2367 (1981)

-

Sol-gel materials as efficient enzyme protectors: Preserving the activity of phosphatases under extreme pH conditions

Frenkel-Mullerad, Hagit,Avnir, David

, p. 8077 - 8081 (2005)

By entrapment in (surfactant modified) silica sol-gel matrixes, alkaline phosphatase (AIP) - naturally with optimum activity at pH 9.5 - was kept functioning at extreme acidic environments as low as pH 0.9, and acid phosphatase (AcP) - naturally with opti

Distance between Metal Centres Affects Catalytic Efficiency of Dinuclear CoIII Complexes in the Hydrolysis of a Phosphate Diester

Bencze, Eva Szusanna,Zonta, Cristiano,Mancin, Fabrizio,Prins, Leonard J.,Scrimin, Paolo

, p. 5375 - 5381 (2018)

Dinuclear CoIII complex catalysed hydrolysis of bis-p-nitrophenylphosphate, a DNA model substrate, is reported. The catalysts were designed in such a way that the two CoIII ions cannot be contemporaneously involved in the complexation of the substrate or transition state. Experimental evidence of the involvement of such a remote metal centre in the catalysis of the hydrolysis of a phosphate diester is provided. This contribution amounts to a ca. 64-fold rate acceleration for the second-order rate constants of the best dinuclear complex over the mononuclear one, which is apparently due to general acid or H-bonding catalysis. Furthermore, there is significant distance dependence for this catalytic contribution and, in this case, it appears that the best distance (as estimated by DFT calculations) is ca. 7.7 ?. This may indicate that the presence of metal centres in close proximity, as required for mechanism proposals in which all metals are directly involved in transition-state coordination, is not the only option for rate acceleration in natural phosphate hydrolysis.

The use of isocyanide-based multicomponent reaction for covalent immobilization of: Rhizomucor miehei lipase on multiwall carbon nanotubes and graphene nanosheets

Mohammadi, Mehdi,Ashjari, Maryam,Garmroodi, Maryam,Yousefi, Maryam,Karkhane, Ali Asghar

, p. 72275 - 72285 (2016)

We describe here a novel and simple method for making bioconjugation and immobilization of Rhizomucor miehei lipase (RML) on carboxylated multiwall carbon nanotubes (MWCNT-COOH) and carboxylated graphene nanosheets (Gr-COOH) by using an isocyanide-based f

Metal-Catalyzed Intramolecular Hydrolysis of Phosphate Esters

Kady, Ismail O.,Tan, Biao

, p. 4031 - 4034 (1995)

A tridentate water-soluble phosphotriester ligand has been synthesized.Kinetic studies have shown that divalent metal ions dramatically enhance the rate of hydrolysis of such phosphotriester at 25 degC and pH 8.0 via intramolecular nucleophilic attack by

Catalysis by mont K-10 supported silver nanoparticles: A rapid and green protocol for the efficient ipso-hydroxylation of arylboronic acids

Begum, Tahshina,Gogoi, Ankur,Gogoi, Pradip K.,Bora, Utpal

, p. 95 - 97 (2015)

A mild and efficient methodology has been developed for the ipso-hydroxylation of arylboronic acids using montmorillonite K-10 supported silver nanoparticles (AgNPs) as catalyst and aqueous H2O2 as oxidant. The reactions were performed at room temperature within short reaction time under solvent- and base-free conditions. This catalyst shows good reusability.

A New Semysynthetic Esterase

Zemel, Haya

, p. 1875 - 1876 (1987)

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Mobilized lipase enzymatic biosensor for the determination of Chlorfenvinphos and Malathion in contaminated water samples: A voltammetric study

Gangadhara Reddy,Madhavi,Kumara Swamy

, p. 181 - 186 (2014)

Concentration levels of organophosphorus pesticides like Chlorfenvinphos and Malathion were determined by lipase enzyme inhibition method. The developed enzymatic method was purely based on in situ generation of p-Nitrophenol by enzymatic hydrolysis of p-

Immobilization of lipase from Burkholderia cepacia into calcium carbonate microcapsule and its use for enzymatic reactions in organic and aqueous media

Fujiwara, Masahiro,Shiokawa, Kumi,Yotsuya, Koji,Matsumoto, Kazutsugu

, p. 94 - 100 (2014)

We disclosed a useful procedure for the immobilization of a lipase from Burkholderia cepacia based on its encapsulation into vaterite calcium carbonate microcapsule. The immobilized enzyme had an adequate activity for the hydrolysis of 4-nitrophenyl aceta

Purification and characterization of thermostable α-galactosidase from Ganoderma lucidum

Sripuan, Thida,Aoki, Kazuhiro,Yamamoto, Kenji,Tongkao, Dararat,Kumagai, Hidehiko

, p. 1485 - 1491 (2003)

α-Galactosidase was purified from a fresh fruiting body of Ganoderma lucidum by precipitation with ammonium sulfate and column chromatographies with DEAE-Sephadex and Con A-Sepharose. The purified enzyme was homogeneous on polyacrylamide gel electrophoresis. Its N-terminal amino acid sequence was similar to that of Mortierella vinacea α-galactosidase. The molecular mass of the enzyme was about 56 kDa by SDS-polyacrylamide gel electrophoresis, and about 249 kDa by gel filtration column chromatography. The optimum pH and temperature were 6.0 and 70°C, respectively. The enzyme was fully stable to heating at 70°C for 30 min. It hydrolyzed p-nitrophenyl-α-D- galactopyranoside (Km = 0.4 mM) but hydrolyzed little o-nitrophenyl-α-D-galactopyranoside. It also hydrolyzed melibiose, raffinose, and stachyose. The enzyme catalyzed the transgalactosylation reaction which synthesized melibiose. The product was confirmed by various analyses.

Characterization of one novel microbial esterase WDEst9 and its use to make l-methyl lactate

Wang, Yilong,Xu, Shan,Li, Renqiang,Sun, Aijun,Zhang, Yun,Sai, Ke,Hu, Yunfeng

, p. 190 - 200 (2019)

Chiral lactic acids and their ester derivatives are crucial building blocks and intermediates for the synthesis of a great variety of valuable functional materials and pharmaceuticals. Before our study, the reports about the enantioselective preparation of pure L-lactic acid and its ester derivatives through direct hydrolysis of racemic substrate were quite rare. Herein, we heterologously expressed and functionally characterized one novel microbial esterase WDEst9 from Dactylosporangium aurantiacum, which exhibited high resistance to diverse metal ions, organic solvents, surfactants, NaCl and KCl. We further utilized WDEst9 as a green biocatalyst in the kinetic resolution of (±)-methyl lactate through direct hydrolysis and generated L-methyl lactate with high enantiomeric excess (e.e. >99%) and high yield (>86%) after process optimization. Notably, the enantioselectivity of WDEst9 was opposite than that of two previously reported esterases PHE14 and BSE01701 that can generate D-methyl lactate though kinetic resolution of (±)-methyl lactate. Microbial esterase WDEst9 is a promising green biocatalyst in the preparation of valuable chiral chemicals and opens the door for the identification of useful industrial enzymes and biocatalysts from the genus Dactylosporangium.

Supramolecular catalytic systems based on anionic amphiphiles and polyethyleneimine for hydrolytic cleavage of phosphorus ester bonds

Zakharova,Valeeva,Ibragimova,Voronin,Kudryavtseva,Syakaev,Kazakova,Morozova,Makarova,Mel'Nikova,Zemnyakova,Konovalov

, p. 374 - 382 (2008)

Self-organization in individual and binary systems based on polyethyleneimine (PEI) and amphiphilic sulfonatocalix[4]resorcinarene was studied by conductometry, tensiometry, dynamic light scattering, and 1H NMR spectroscopy. The critical concen

A facile and selective deprotection of tert-butyldimethylsilyl ethers of phenols using triethylamine N-oxide

Zubaidha,Bhosale,Hashmi

, p. 7277 - 7279 (2002)

Aryl TBS ethers can be cleaved selectively in high yields in the presence of alkyl TBS ethers by employing triethylamine N-oxide.

Huebner,Hall

, p. 1221 (1875)

Asymmetric hydrolysis of dimethyl-3-phenylglutarate in sequential batch reactor operation catalyzed by immobilized Geobacillus thermocatenulatus lipase

Guajardo, Nadia,Bernal, Claudia,Wilson, Lorena,Cabrera, Zaida

, p. 21 - 26 (2015)

Abstract The main goal of this work was to study the stereoselective behavior of immobilized Geobacillus thermocatenulatus lipase (BTL2) in a sequential batch reactor using the partial and asymmetric hydrolysis of dimethyl-3 phenylglutarate (DMFG) as a mo

Regio-selective mono nitration of phenols with ferric nitrate in room temperature ionic liquid

Rajagopal,Srinivasan

, p. 961 - 966 (2003)

The mono nitration of phenols with ferric nitrate has been achieved in high regio-selectivities in 1-3 h at 30-60°C using the ionic liquid 1,3-di-n-butylimidazolium tetraflouroborate [bbim]BF4 as the solvent. In particular, excellent para selectives of the order of 76-86% for unsubstituted, ortho and meta-substituted phenols were observed.

Microwave-assisted copper-catalyzed hydroxylation of aryl halides in water

Ke, Fang,Chen, Xiaole,Li, Zhengkai,Xiang, Haifeng,Zhou, Xiangge

, p. 22837 - 22840 (2013)

A simple and efficient protocol for microwave-assisted copper-catalyzed hydroxylation of aryl halides is developed. A variety of phenols can be obtained in moderate to excellent yields of up to 95%. Its application is performed to synthesize 2,3-dihydroxy-1,4-naphthoquinone, which displays significant anti-proliferation effect.

Purification and characterization of a highly selective glycyrrhizin-hydrolyzing β-glucuronidase from Penicillium purpurogenum Li-3

Zou, Shuping,Liu, Guiyan,Kaleem, Imdad,Li, Chun

, p. 358 - 363 (2013)

A novel β-glucuronidase from filamentous fungus Penicillium purpurogenum Li-3 was purified to electrophoretic homogeneity by ultrafiltration, ammonium sulfate precipitation, DEAE-cellulose ion exchange chromatography, and Sephadex G-100 gel filtration wit

Effect of Acyl Substituents on the Reaction Mechanism for Aminolyses of 4-Nitrophenyl X-Substituted Benzoates

Um, Ik-Hwan,Min, Ji-Sook,Ahn, Jung-Ae,Hahn, Hyun-Joo

, p. 5659 - 5663 (2000)

Second-order rate constants (kN) have been measured spectrophotometrically for the reaction of 4-nitrophenyl X-substituted benzoates with a series of alicyclic secondary amines in H2O containing 20 mol % dimethyl sulfoxide at 25.0°C.

Microwave-assisted activation and modulator removal in zirconium MOFs for buffer-free CWA hydrolysis

Kalinovskyy,Cooper,Main,Holder,Blight

, p. 15704 - 15709 (2017)

A novel, facile and efficient method was developed for the activation of acetic acid modulated zirconium MOFs. The protocol involves briefly heating the material in water using microwave irradiation. MOF-808, DUT-84 and UiO-66 were all activated in this manner to remove the modulator and organic solvent from the framework post synthesis, with retention of MOF integrity post activation. The degree of activation was characterised by the use of TGA and NMR. The catalytic activity of the activated MOFs and their non-activated counterparts was investigated for chemical warfare agent (CWA) hydrolysis. Upon activation, an increase in the rate of hydrolysis was observed in the degradation of CWA simulant dimethyl 4-nitrophenyl phosphate (DMNP). MOF-808 and DUT-84 were also screened as catalysts for the hydrolysis of the V-series agent VM, with remarkable half-lives obtained for MOF-808 in the absence of any buffers. Currently employed MOF activation procedures involve the use of additional organic solvents post synthesis; we believe this method to be ideally efficacious for the organic desolvation of zirconium MOFs and removing modulator additives.

Variants of Phosphotriesterase for the Enhanced Detoxification of the Chemical Warfare Agent VR

Bigley, Andrew N.,Mabanglo, Mark F.,Harvey, Steven P.,Raushel, Frank M.

, p. 5502 - 5512 (2015)

The V-type organophosphorus nerve agents are among the most hazardous compounds known. Previous efforts to evolve the bacterial enzyme phosphotriesterase (PTE) for the hydrolytic decontamination of VX resulted in the identification of the variant L7ep-3a,

Green catalysts derived from agricultural and industrial waste products: The preparation of phenols from CsOH and Aryl iodides using CuO on mesoporous silica

Chan, Chien-Ching,Chen, Yan-Wun,Su, Chi-Shen,Lin, Hong-Ping,Lee, Chin-Fa

, p. 7288 - 7293 (2011)

The synthesis of CuO catalysts supported on mesoporous silica derived from rice husks and semiconductor copper from chemical mechanical planarization (Cu-CMP) wastewater is described. These catalysts are active for the coupling reaction of CsOH with aryl iodides. Low catalyst loading (1 mol-%) without the need for ancillary ligands make these very attractive "green" catalysts. The synthesis of CuO catalysts supported on mesoporous silica derived from rice husks and semiconductor copper from chemical mechanical planarization (Cu-CMP) wastewater is described. These catalysts are active for the coupling reaction of CsOH with aryl iodides. Low catalyst loading (1 mol-%) without the need for ancillary ligands make these very attractive "green" catalysts. Copyright

Dramatic hyperactivation of lipase of Thermomyces lanuginosa by a cationic surfactant: Fixation of the hyperactivated form by adsorption on sulfopropyl-sepharose

Moreno-Perez, Sonia,Ghattas, Nesrine,Filice, Marco,Guisan, Jose M.,Fernandez-Lorente, Gloria

, p. 199 - 203 (2015)

Soluble lipase from Thermomyces lanuginosa (TLL) was dramatically hyper-activated by a cationic surfactant, cetyltrimethylammonium bromide (CTAB). The greatest hyperactivation (above 340-fold) was observed with 0.005% CTAB. In addition to that, very high

MIL-101(Cr) with incorporated polypyridine zinc complexes for efficient degradation of a nerve agent simulant: spatial isolation of active sites promoting catalysis

Zhang, Kai,Cao, Xingyun,Zhang, Zhiyan,Cheng, Yong,Zhou, Ying-Hua

, p. 1995 - 2000 (2021)

Development of an efficient catalyst for degradation of organophosphorus toxicants is highly desirable. Herein, an MIL-101(Cr)LZn catalyst was fabricated by incorporating polypyridine zinc complexes into a MOF to achieve the spatial isolation of active si

Tuning the properties of cyclen based lanthanide complexes for phosphodiester hydrolysis; the role of basic cofactors

Fanning, Ann-Marie,Plush, Sally E.,Gunnlaugsson, Thorfinnur

, p. 3791 - 3793 (2006)

The synthesis of several cyclen based lanthanide [Eu(iii) and La(iii)] complexes is described; these metallo ribonuclease mimics are based on the use of alkyl amines as pendent arms, which give rise to fast hydrolysis within the physiological pH range of

-

Pictet

, p. 815 (1893)

-

Redox regulation of protein tyrosine phosphatase 1B by peroxymonophosphate (=O3POOH)

LaButti, Jason N.,Chowdhury, Goutam,Reilly, Thomas J.,Gates, Kent S.

, p. 5320 - 5321 (2007)

Reversible phosphorylation of tyrosine residues serves as a biochemical "switch" that alters the functional properties of many proteins involved in cellular signal transduction processes. Protein tyrosine phosphatases (PTPs) catalyze the removal of phosph

A mild, highly selective and remarkably easy procedure for deprotection of aromatic acetates using ammonium acetate as a neutral catalyst in aqueous medium

Ramesh,Mahender,Ravindranath,Das, Biswanath

, p. 1049 - 1054 (2003)

Ammonium acetate was found to catalyze efficiently the selective deprotection of aromatic acetates in the presence of various sensitive functionalities in aqueous methanol under neutral conditions at room temperature to yield the corresponding phenols in excellent yields. The method has been utilized for deprotection of acetates of several naturally occurring bioactive phenolic compounds and for preparation of venkatasin, a natural coumarino-lignan, from the anticancer compound cleomiscosin A.

Deprotection of tetrahydropyranyl ethers with montmorillonite K-10 clay in methanol

Taniguchi, Takahiko,Kadota, Kohei,Elazab, Adel S.,Ogasawara, Kunio

, p. 1247 - 1248 (1999)

A variety of tetrahydropyranyl (THP) ethers are removed by Montmorillonite K-10 clay in methanol at room temperature to give alcohols. It has been shown that the THP ethers carrying epoxy, methoxymethoxy (MOMO), tertbutyldiphenylsiloxy (TBDP-SO-), acetoxy (AcO-) and benzoyloxy (BzO-) functionalities are stable under the conditions, while the ethers carrying ketal, tertbutyldimethylsioxy (TBSO-) and β,β,β-trichloroethylimidoxy [CCl3C(=NH)O-] functionalities are unstable.

Functional and structural characterization of an α-?-arabinofuranosidase from Thermothielavioides terrestris and its exquisite domain-swapped β-propeller fold crystal packing

Camargo, Suelen,Mulinari, Evandro J.,de Almeida, Leonardo R.,Bernardes, Amanda,Prade, Rolf A.,Garcia, Wanius,Segato, Fernando,Muniz, Jo?o R.C.

, (2020)

The fungus Thermothielavioides terrestris plays an important role in the global carbon cycle with enzymes capable of degrading polysaccharides from biomass, therefore an attractive source of proteins to be investigated and understood. From cloning to a three-dimensional structure, we foster a deeper characterization of an α-?-arabinofuranosidase, a glycoside hydrolase from the family 62 (TtAbf62), responsible to release arabinofuranose from non-reducing ends of polysaccharides. TtAbf62 was tested with synthetic (pNP-Araf) and polymeric substrates (arabinan and arabinoxylan), showing optimal temperature and pH (for pNP-Araf) of 30 °C and 4.5–5.0, respectively. Kinetic parameters revealed different specific activity for the three substrates, with a higher affinity for pNP-Araf (KM: 4 ± 1 mM). The hydrolyzing activity of TtAbf62 on sugarcane bagasse suggests high efficiency in the decomposition of arabinoxylan, abundant hemicellulose presented in the sugarcane cell wall. The crystal packing of TtAbf62 reveals an exquisite domain swapping, located at the supramolecular arrangement through a disulfide bond. All crystallographic behaviors go against its monomeric state in solution, indicating a crystal-induced artifact. Structural information will form the basis for further studies aiming the development of optimized enzymatic properties to be used in biotechnological applications.

Acceptor-induced modification of regioselectivity in CGTase-catalyzed glycosylations of p-nitrophenyl-glucopyranosides

Strompen, Simon,Miranda-Molina, Alfonso,López-Munguía, Agustín,Castillo, Edmundo,Saab-Rincón, Gloria

, p. 46 - 54 (2015)

Cyclodextrin glycosyltransferases (CGTase) are reported to selectively catalyze α(1→4)-glycosyl transfer reactions besides showing low hydrolytic activity. Here, the effect of the anomeric configuration of the glycosyl acceptor on the regioselectivity of

A Water-Bridged Cysteine-Cysteine Redox Regulation Mechanism in Bacterial Protein Tyrosine Phosphatases

Bertoldo, Jean B.,Rodrigues, Tiago,Dunsmore, Lavinia,Aprile, Francesco A.,Marques, Marta C.,Rosado, Leonardo A.,Boutureira, Omar,Steinbrecher, Thomas B.,Sherman, Woody,Corzana, Francisco,Terenzi, Hernán,Bernardes, Gon?alo J.L.

, p. 665 - 677 (2017)

The emergence of multidrug-resistant Mycobacterium tuberculosis (Mtb) strains highlights the need to develop more efficacious and potent drugs. However, this goal is dependent on a comprehensive understanding of Mtb virulence protein effectors at the mole

Kinetics and mechanism of the aminolysis of methyl 4-nitrophenyl, methyl 2,4-dinitrophenyl, and phenyl 2,4-dinitrophenyl carbonates

Castro, Enrique A.,Aliaga, Margarita,Campodonico, Paola,Santos, Jose G.

, p. 8911 - 8916 (2002)

The reactions of methyl 4-nitrophenyl carbonate (MNPC) with a series of secondary alicyclic amines (SAA) and quinuclidines (QUIN), methyl 2,4-dinitrophenyl carbonate (MDNPC) with QUIN and 1-(2-hydroxyethyl)piperazinium ion (HPA), and phenyl 2,4-dinitrophe

Ketene-forming eliminations from aryl bis(4′-chlorophenyl)acetates promoted by R2NH-R2NH2+ in aqueous MeCN. Change of mechanism

Pyun, Sang Yong,Lee, Dong Choon,Kim, Ju Chang,Cho, Bong Rae

, p. 2734 - 2738 (2003)

Elimination reactions of (4′-ClC6H4) 2CHCO2C6H3-2-X-4-NO2 promoted by R2NH-R2NH2+ in 70 mol% MeCN (aq.) have been studied kinetically.

-

Hawthorne,Hammond

, p. 2549 (1955)

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Activity of Candida rugosa lipase immobilized on γ-Fe2O3 magnetic nanoparticles

Dyal, Ansil,Loos, Katja,Noto, Mayumi,Chang, Seung W.,Spagnoli, Chiara,Shafi, Kurikka V. P. M.,Ulman, Abraham,Cowman, Mary,Gross, Richard A.

, p. 1684 - 1685 (2003)

We report the stability and enzymatic activity of Candida rugosa Lipase (E.C.3.1.1.3) immobilized on γ-Fe2O3 magnetic nanoparticles. The immobilization strategies were either reacting the enzyme amine group with a nanoparticle surfac

Purification and partial characterization of acetic acid esterase from malted finger millet (Eleusine coracana, indaf-15)

Madhavi Latha,Muralikrishna

, p. 895 - 902 (2007)

Acetic acid esterase (EC 3.1.1.6) cleaves the acetyl groups substituted at O-2/O-3 of the xylan backbone of arabinoxylans and is known to modulate their functional properties. To date, this enzyme from cereals has not received much attention. In the present study, acetic acid esterase from 72 h ragi malt was isolated and purified to apparent homogeneity by a four-step purification, i.e., ammonium sulfate precipitation, DEAE-cellulose, Sephacryl S-200, and phenyl-Sepharose column chromatography, with a recovery of 0.36% and a fold purification of 34. The products liberated from a-NA and PNPA by the action of purified ragi acetic acid esterase were authenticated by ESI-MS and 1H NMR. The pH and temperature optima of the enzyme were found to be 7.5 and 45 °C, respectively. The enzyme is stable in the pH range of 6.0-9.0 and temperature range of 30-40 °C. The activation energy of the enzymatic reaction was found to be 7.29 kJ mor-1. The apparent Km and Vmax of the purified acetic acid esterase for a-NA were 0.04 μM and 0.175 μM min-1 mL-1, respectively. The molecular weight of the native enzyme was found to be 79.4 kDa by GPC whereas the denatured enzyme was found to be 19.7 kDa on SDS, indicating it to be a tetramer. EDTA, citric acid, and metal ions such as Fe+3 and Cu +2 increased the activity while Ni+2, Ca+2, Co+2, Ba+2, Mg+2, Mn+2, Zn +2, and AI +3 reduced the activity. Group-specific reagents such as eserine and PCMB at 25 mM concentration completely inhibited the enzyme while iodoacetamide did not have any effect. Eserine was found to be a competitive inhibitor.

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Loebl,Stein,Weiss

, p. 2074 (1949)

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Phosphoester hydrolysis promoted by quinoline functionalized Ni(II) and Zn(II) complexes

Junaid, Qazi Mohammad,Sureshbabu, Popuri,Sabiah, Shahulhameed

, p. 1550 - 1562 (2021)

A quinoline functionalized nitrogen-based bidentate ligand (L) was synthesized and used for the preparation of mononuclear Ni(II) and Zn(II) complexes which differ only by the halide ion attached to the respective metal center. All complexes of this serie

Nitration of phenolic compounds and oxidation of hydroquinones using tetrabutylammonium chromate and dichromate under aprotic conditions

Pourali, Ali Reza,Goli, Arezou

, p. 63 - 67 (2011)

In this work, we have reported a mild, efficient and selective method for the mononitration of phenolic compounds using sodium nitrite in the presence of tetrabutylammonium dichromate (TBAD) and oxidation of hydroquinones to quinones with TBAD in CH2Cl2. Using this method, high yields of nitrophenols and quinones were obtained under neutral aprotic conditions. Tetrabutylammonium chromate (TBAC) can also be used as oxidant at same conditions. Indian Academy of Sciences.

Purification and characterization of purple acid phosphatase PAP1 from dry powder of sweet potato

Kusudo, Tatsuya,Sakaki, Toshiyuki,Inouye, Kuniyo

, p. 1609 - 1611 (2003)

Purple acid phosphatase (PAP) was purified from sweet potato dry powder, which is used as a food additive. Spectrometric and enzymatic analyses, and analysis of the amino-terminal sequence indicated that the purified purple acid phosphatase was PAP1. High

A kinetic analysis of hepatic microsomal activation of parathion and chlorpyrifos in control and phenobarbital-treated rats.

Ma,Chambers

, p. 63 - 68 (1995)

A kinetic analysis of cytochrome P450-mediated desulfuration (activation) or dearylation (detoxication) showed that rat hepatic microsomes have a greater capacity to detoxify and a lower capacity to activate chlorpyrifos compared to parathion. Kinetic curves for the desulfuration of both parathion and chlorpyrifos were biphasic; Kmapps of 0.23 and 71.3 microM were calculated for parathion, and 1.64 and 50.4 microM for chlorpyrifos. While phenobarbital (PB) exposure seemed to generally lower the Kmapps for desulfuration except for the low Km activity on chlorpyrifos, the results were not statistically significant. While the low Km activity contributed 44 and 60% of the control Vmax for parathion and chlorpyrifos, respectively, it contributed 50 and 17% in PB-treated rats. These studies have indicated the presence of a low Km activity capable of functioning at very low substrate concentrations. A single dearylation Kmapp was calculated, 56.0 and 9.8 microM for parathion and chlorpyrifos, respectively. Phenobarbital exposure seemed to raise the Kmapps of dearylation; however, again, the results were not statistically significant. While numerous biochemical factors contribute to the overall toxicity levels of phosphorothionate insecticides, the in vitro efficiencies of hepatic microsomal desulfuration and dearylation of parathion and chlorpyrifos correspond to the acute toxicity levels.

Structural studies of a thermophilic esterase from a new Planctomycetes species, Thermogutta terrifontis

Sayer, Christopher,Isupov, Michail N.,Bonch-Osmolovskaya, Elizaveta,Littlechild, Jennifer A.

, p. 2846 - 2857 (2015)

Thermogutta terrifontis esterase (TtEst), a carboxyl esterase identified in the novel thermophilic bacterium T. terrifontis from the phylum Planctomycetes, has been cloned and over-expressed in Escherichia coli. The enzyme has been characterized biochemic

Solvent Effect on Activation Parameters for the Neutral Hydrolysis of Phenyl Trifluoroacetates in Aqueous Acetonitrile

Neuvonen, Helmi

, p. 1723 - 1726 (1987)

Rates of neutral hydrolysis of phenyl, 4-nitrophenyl, and 2,4-dinitrophenyl trifluoroacetates in acetonitrile-water mixtures(xMeCN=0.39-0.97) have been measured.The free energies of activation increase smoothly upon increasing the acetonitrile content of the medium while the enthalpies and entropies of activation show a more complex but partially compensating behaviour.For phenyl trifluoroacetate both ΔH and ΔS pass through an inflexion point around xMeCN=0.6.For 4-nitrophenyl and 2,4-dinitrophenyl trifluoroacetates a minimum value possibly occurs both in ΔH and ΔS around xMeCN=0.9-0.95, but it is clearly observed in ΔH at xCN=0.92 for the former ester and in ΔS at xMeCN=0.94 for the latter ester.The activation parameters are discussed in terms of solvent structure.The extreme values are mainly attributed to changes in the thermodynamic functions of transfer of the transition state of the hydrolysis reaction from water to acetonitrile-water mixtures.

Transition-State Properties and Rate-Limiting Processes in the Acetylation of Acetylcholinesterase by Natural and Unnatural Substrates

Hogg, John L.,Elrod, James P.,Schowen, Richard L.

, p. 2082 - 2086 (1980)

The acetylation of acetylcholinesterase at pH 7.5 and 25.00 deg C proceeds at the same rate to within a few percent for acetylcholine, CD3CO2CH2CH2N(CH3)3+, CH3CO2CD2CH2N(CH3)3+, and CH3CO2CH2CD2N(CH3)3+ and possibly sligh

Sodium trimethyl silanoate. A hydroxyl synthon for fluoride S(n)Ar type displacements from anthracene-9,10-diones, benz[g]isoquinoline-5-10-diones and nitrobenzenes

Krapcho, A. Paul,Waterhouse, David

, p. 3415 - 3422 (1998)

Treatment of fluoroanthracene-9,10-diones, fluorobenz[g]isoquinoline- 5,10-diones and 1- or 4-fluoronitrobenzenes with sodium trimethylsilanoate in THF followed by acidification readily yields the corresponding hydroxyl analogues.

A fast radical chain mechanism in the polyfluoroalkoxylation of aromatics through NO2 group displacement. Mechanistic and theoretical studies

Tejero, Ismael,Huertas, Imma,Gonzalez-Lafont, Angels,Lluch, Jose M.,Marquet, Jordi

, p. 1718 - 1727 (2005)

(Chemical Equation Presented) Introduction of polyfluoroalkoxy and polyfluoroalkylthio substituents in aromatic rings can be achieved with mild conditions and short times thorough reaction of concentrated solutions of dinitrobenzenes in DMF with polyfluor

Micellar Activation of Nucleophilic Cu(2+)-complexes of Surfactant Imidazole Ligands by Co-surfactants for the Hydrolysis of p-Nitrophenyl Picolinate. Importance of the Charge Site on Surfactant Ligand

Ogino, Kenji,Yoshida, Toshiharu,Nishi, Kazuyoshi,Fujita, Tsunehisa,Tagaki, Waichiro

, p. 341 - 344 (1991)

The micellar activation of the nucleophilic Cu(2+)-complexes of four surfactant imidazole ligands has been examined for the hydrolysis of p-nitrophenyl picolinate.A dramatic difference in the effect of co-surfactant was observed between the ligands having

Purification and characterization of alkaline phosphatase from lactic acid bacteria

Chu, Yu-Hao,Yu, Xin-Xin,Jin, Xing,Wang, Yu-Tang,Zhao, Duo-Jia,Zhang, Po,Sun, Guang-Mei,Zhang, Ying-Hua

, p. 354 - 360 (2019)

Alkaline phosphatase (ALP) excreted from lactic acid bacteria (LAB) showed the ability to degrade organophosphorus pesticides. This study reported the first purification and characterization of ALP from LAB. The molecular weight of ALP was estimated to be

Pressure effects on the hydrolysis of p-nitrophenyl and 2-naphthyl acetates catalyzed by cyclodextrins

Taniguchi, Yoshihiro,Makimoto, Syoichi,Suzuki, Keizo

, p. 3469 - 3472 (1981)

The rates of the hydrolysis of p-nitrophenyl acetate (PNPA) and 2-naphthyl acetate (2-NaA) catalyzed by α-, β-, and γ-cyclodextrins (CDs) were measured at pressures up to 2 kbar at 25°C and pH 8.3 in 0.02 M Tris buffer solution. At 1 bar, the rate of PNPA followed the enzymatic kinetics for α- and β-CDs and that of 2-NaA followed those for β- and γ-CDs. The substrate binding constant, K, for the 2-NaA-β-CD system decreased with increasing pressure up to 1 kbar, but the K values for other systems were constant regardless of the magnitude of pressure. The rate constants of the acylation process, k2, for all systems up to 2 kbar increased monotonously up to 2 kbar. From the pressure dependence of K, the volume changes, ΔV, accompanying the formation of the inclusion complexes at 1 bar were 0 ± 2 cm3/mol, except for 10 ± 2 cm3/mol for 2-NaA-β-CD. The activation volumes, ΔV*, for the cleavages of ester molecules in the acylation process were in the range from -17.5 ± 2 cm3/mol for 2-NaA-β-CD to -13 ± 2 cm3/mol for PNPA-β-CD. The volume changes accompanying the formation of the inclusion complexes were explained either by the hydrophobic interaction between substrates and CD or by the conformational change of CD molecules in the inclusion process. It is suggested from the activation volumes in the acylation that the reaction process is classified into two types, one involving loose inclusion complexes for PNPA-β-CD and 2-NaA-γ-CD and the other involving tight complexes for PNPA-α-CD and 2-NaA-β-CD. The tight complexes seemed to be more solvated than the loose ones.

Novel properties of cooperative dinuclear zinc(II) ions: The selective recognition of phosphomonoesters and their P-O ester bond cleavage by a new dinuclear zinc(II) cryptate

Koike, Tohru,Inoue, Masaki,Kimura, Eiichi,Shiro, Motoo

, p. 3091 - 3099 (1996)

A propanol-bridged octaazacryptand (26-hydroxy-1,4,7,10,13,16,19,22-octaazabicyclo[11.11.3]heptacosane, HL) has been synthesized from diethylenetriamine and [2-oxo-6-(aminomethyl)morpholyl]-N,N',N'-triacetic acid triethyl ester by refluxing in MeOH follow

Convenient reduction of nitrobenzenes to anilines using electrochemically generated nickel

Yasuhara,Kasano,Sakamoto

, p. 2301 - 2303 (1999)

The reduction of nitrobenzenes with electrogenerated nickel in DMF gave anilines without affecting the alkenyl, alkynyl, halo, acetyl, methoxy, cyano, ethoxycarbonyl, formyl, benzyloxy, and phenylsulfonylamino groups at room temperature in a short time. The nickel was easily prepared by electrolysis in 0.3 M Et4NBF4-DMF solution under an argon atmosphere at a constant current (10 mA/cm2) and can be stored under argon at -20 °C for at least a week. The reduction of nitrobenzenes with electrogenerated nickel in DMF gave anilines without affecting the alkenyl, alkynyl, halo, acetyl, methoxy, cyano, ethoxycarbonyl, formyl, benzyloxy, and phenylsulfonylamino groups at room temperature in a short time. The nickel was easily prepared by electrolysis in 0.3 M Et4NBF4-DMF solution under an argon atmosphere at a constant current (10 mA/cm2) and can be stored under argon at -20 °C for at least a week.

Telluroxides exhibit hydrolysis capacity

Dong, Zeyuan,Li, Xiangqiu,Liang, Kai,Mao, Shizhong,Huang, Xin,Yang, Bing,Xu, Jiayun,Liu, Junqiu,Luo, Guimin,Shen, Jiacong

, p. 606 - 609 (2007)

It has long been known that tellurium compounds are rather toxic to living organisms, and tellurium has not been found in natural biomacromolecules to date. The principles of telluride toxicity in biological processes are still controversial partly because of the lack of information on the biochemical features of tellurium. In this contribution, we report our finding for the first time that telluroxides exhibit hydrolysis capacity. For instance, 6,6′-telluroxy-bis(6-deoxy-β-cyclodextrin) acts as a hydrolase mimic and shows a significant rate acceleration of 106 000 for the hydrolysis of 4,4′-dinitrodiphenyl carbonate.

Nanoisozymes: The Origin behind Pristine CeO2 as Enzyme Mimetics

Tan, Zicong,Chen, Yu-Cheng,Zhang, Jieru,Chou, Jyh-Pin,Hu, Alice,Peng, Yung-Kang

, p. 10598 - 10606 (2020)

It is known that the interplay between molecules and active sites on the topmost surface of a solid catalyst determines its activity in heterogeneous catalysis. The electron density of the active site is believed to affect both adsorption and activation o

Heterogeneous Palladium–Chitosan–CNT Core–Shell Nanohybrid Composite for Ipso-hydroxylation of Arylboronic Acids

Shin, Eun-Jae,Kim, Han-Sem,Joo, Seong-Ryu,Shin, Ueon Sang,Kim, Seung-Hoi

, (2019)

Abstract: A novel palladium-nanohybrid (Pd–Chitosan–CNT) catalytic composite has been developed using CNT–chitosan nanocomposite and palladium nitrate. The prepared catalytic platform displays excellent catalytic reactivity for the ipso-hydroxylation of various arylboronic acids with a mild oxidant aqueous H2O2 at room temperature, affording the corresponding phenols in excellent yields. Significantly, the easy recovery and reusability by simple manipulation demonstrate the green credentials of this catalytic platform. Graphical Abstract: [Figure not available: see fulltext.]

Efficient syntheses of artificial nucleases containing mono-, di- and tri-[12]aneN3 ligating units through click chemistry

Zan, Ju,Yan, Hao,Guo, Zhi-Fo,Lu, Zhong-Lin

, p. 1054 - 1056 (2010)

Mono-, di-, and tri-nucleating [12]aneN3 ligands 3-5 have been efficiently prepared through the copper-mediated click reactions between propargyl modified [12]aneN3 2 and mono-, bis-, and tri-azido compounds. Their corresponding zinc

RECENT DEVELOPMENTS IN CHEMICAL DEPROTECTION OF ESTER FUNCTIONAL GROUPS

Salomon, Claudio J.,Mata, Ernesto G.,Mascaretti, Oreste A.

, p. 3691 - 3734 (1993)

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Metal-Organocatalyst for Detoxification of Phosphorothioate Pesticides: Demonstration of Acetylcholine Esterase Activity

Singh, Amanpreet,Raj, Pushap,Singh, Ajnesh,Dubowski, Jan J.,Kaur, Navneet,Singh, Narinder

, p. 9773 - 9784 (2019)

In recent years, transition metal complexes have been developed for catalytical degradation of a phosphate ester bond, particularly in RNA and DNA; however, less consideration has been given for development of complexes for the degradation of a phosphorot

Thermal and Mechanical Stability of Immobilized Candida antarctica Lipase B: an Approximation to Mechanochemical Energetics in Enzyme Catalysis.

Pérez-Venegas, Mario,Tellez-Cruz, Miriam M.,Solorza-Feria, Omar,López-Munguía, Agustín,Castillo, Edmundo,Juaristi, Eusebio

, p. 803 - 811 (2020)

Very recently, several successful enzymatic processes performed with mechanical activation have been disclosed; that is, despite the mechanical stress caused by High-Speed Ball-Milling, immobilized enzymes can retain activity. In the present study, the effect of thermal and mechanical stress was examined as potential inducers of enzymatic denaturation, when using either free, immobilized, or ground immobilized enzyme. The recorded observations show a remarkable stability of ground immobilized enzyme. Moreover, ground biocatalyst turns out to exhibit an increase of one order of magnitude in the efficiency of the catalytic process, maintaining excellent enantiodiscrimination, without significant activity loss even after four milling cycles. These observations rule out enzyme inactivation as direct consequence of the milling process. Additionally, boosted enzyme efficiency was used to optimize a relatively inefficient chiral amine resolution reaction, achieving a 25 % faster biotransformation (in 45 min) and yielding essentially enantiopure products (ee>99%, E>500).

Novel change in rate-determining step within an E1cB mechanism during aminolysis of a sulfamate ester in acetonitrile

Spillane, William J.,McGrath, Paul,Brack, Chris,Barry, Keith

, p. 1017 - 1018 (1998)

The observation of biphasic Bronsted plots (β1 ca. 0.7 and β2 ca. 0) in the aminolysis (alicyclic amines, pyridines) of 4-nitrophenyl N-benzylsulfamate 1a in MeCN is interpreted as being due to a mechanistic change from (ElcB)ir

Electrochemical-induced hydroxylation of aryl halides in the presence of Et3N in water

Ke, Fang,Lin, Chen,Lin, Mei,Long, Hua,Wu, Mei,Yang, Li,Zhuang, Qinglong

, p. 6417 - 6421 (2021)

A thorough study of mild and environmentally friendly electrochemical-induced hydroxylation of aryl halides without a catalyst is presented. The best protocol consists of hydroxylation of different aryl iodides and aryl bromides by water solution in the presence of Et3N under air, affording the target phenols in good isolated yields. Moreover, aryl chlorides were successfully employed as substrates. This methodology also provides a direct pathway for the formation of deoxyphomalone, which displayed a significant anti-proliferation effect.

Mechanism of Arene Hydroxylation by Vanadium Picolinato Peroxo Complexes

Bonchio, Marcella,Conte, Valeria,Di Furia, Fulvio,Modena, Giorgio,Moro, Stefano

, p. 6262 - 6267 (1994)

The mechanism of the reaction of VO(O2)PIC(H2O)2 (PIC = picolinic acid anion) with benzene and substituted benzenes in CH3CN, affording the corresponding phenols together with dioxygen, has been further investigated.The reaction is a radical chain process whose initiation produces the actual oxidant which may be described as a radical anion derived from the peroxovanadium complex, possessing, however, a marked electrophilic character.In the propagation steps such species react either with the original peroxo complex yielding dioxygen or with the aromatic substrates affording phenols via the formation of an intermediate.

Optimization of immobilization conditions of Thermomyces lanuginosus lipase on styrene-divinylbenzene copolymer using response surface methodology

Aybastier, Oender,Demir, Cevdet

, p. 170 - 178 (2010)

Microbial lipase from Thermomyces lanuginosus (formerly Humicola lanuginosa) was immobilized by covalent binding on a novel microporous styrene-divinylbenzene polyglutaraldehyde copolymer (STY-DVB-PGA). The response surface methodology (RSM) was used to o

The method of integrated kinetics and its applicability to the exo-glycosidase-catalyzed hydrolyses of p-nitrophenyl glycosides

Borisova, Anna S.,Reddy, Sumitha K.,Ivanen, Dina R.,Bobrov, Kirill S.,Eneyskaya, Elena V.,Rychkov, Georgy N.,Sandgren, Mats,St?lbrand, Henrik,Sinnott, Michael L.,Kulminskaya, Anna A.,Shabalin, Konstantin A.

, p. 43 - 49 (2015)

In the present work we suggest an efficient method, using the whole time course of the reaction, whereby parameters kcat, Km and product KI for the hydrolysis of a p-nitrophenyl glycoside by an exo-acting glycoside hydrola

SELECTIVE FUNCTIONALISATION PART 10. THE NITRATION OF PHENOLS BY PYRIDDINE DERIVATIVES CARRYING A TRANSFERABLE NITRO GROUP

Pervez,Humayun,Onyiriuka, Samuel O.,Rees, Lilias,Rooney, James R.,Suckling, Colin J.

, p. 4555 - 4568 (1988)

Pyridinium salts bearing carboxylate side chains and pyridones are shown to react with nitronium tetrafluoroborate or nitrogen dioxide to yield activated intermediates capable of selectively nitrating phenol ortho to the hydroxyl group with virtually comp

Hydrolysis of p-Nitrophenyl Esters by Histidine-containing Linear and Cyclic Peptides

Kodaka, Masato

, p. 3857 - 3858 (1983)

Hydrolysis of p-nitrophenyl acetate (PNPA) and p-nitrophenyl hexanoate (PNPH) catalyzed by several linear and cyclic peptides containing histidine and other amino acid residues was studied.The catalytic activity of the peptides was less than that of imida

Purification and properties of a β-galactosidase from carambola fruit with significant activity towards cell wall polysaccharides

Balasubramaniam, Sumathi,Lee, Heng Chin,Lazan, Hamid,Othman, Roohaida,Ali, Zainon Mohd.

, p. 153 - 163 (2005)

β-Galactosidase (EC. 3.2.1.23) from ripe carambola (Averrhoa carambola L. cv. B10) fruit was fractionated through a combination of ion exchange and gel filtration chromatography into four isoforms, viz. β-galactosidase I, II, III and IV. This β-galactosid

MONONITRATION DE PHENOLS PAR DES NITRATES METALLIQUES

Poirier, Jean-Marie,Vottero, Catherine

, p. 1415 - 1422 (1989)

A new and practical route to mononitrphenol in high yields is described using commercially aviable hydrated metallic nitrates.According to the metallic nitrate used, this reaction can yield regiospecifically the ortho-nitrophenol or regioselectively the para-nitrophenol.This method is successfully applied to some phenolic derivatives, in particular to the preparation of 2-nitroestrone.Sodium nitrate with ferric chloride or with titane tetrachloride allows mononitration of phenol.

Spectroscopic investigations on the interaction between cadmium telluride semiconductor nanoparticle and bovine alkaline phosphatase

Babaknejad, Nasim,Shareghi, Behzad,Saboury, Ali Akbar

, p. 81 - 90 (2019)

The interaction of enzymes with nanoparticles is important in the field of biotechnology and medicine. Due to the various uses of cadmium telluride nanoparticle in protein science, biotechnology and biophysical chemistry, drug delivery, and cellular imagi

Alkaline-earth metal complexes of thiol-pendant crown ethers as turnover catalysts of ester cleavage

Breccia, Perla,Cacciapaglia, Roberta,Mandolini, Luigi,Scorsini, Carla

, p. 1257 - 1261 (1998)

Methanolysis of pNPOAc under moderately alkaline conditions is catalysed by the alkaline-earth metal ion (Ca, Sr, Ba) complexes of 2-(mercaptomethyl)-18-crown-6 according to biphasic kinetics in which an initial burst of pNPOH release is followed by a zer

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Stoochnoff,B.A.,Benoiton,N.L.

, p. 21 - 24 (1973)

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Role of metal cations and oxyanions in the regulation of protein arginine phosphatase activity of YwlE from Bacillus subtilis

Huang, Biling,Huang, Chenyang,Huang, Shaohua,Liao, Xinli,Liu, Yan,Zhang, Yumeng,Zhao, Mingxiao,Zhao, Yufen,Zhao, Zhixing

, (2020)

Protein arginine phosphorylation (pArg) is a relatively novel posttranslational modification. Protein arginine phosphatase YwlE negatively regulates arginine phosphorylation and consequently induces the expression of stress-response genes that are crucial for bacterial stress tolerance and pathogenic homolog Staphylococcus aureus virulence. However, little is known about the factors that affect the enzymatic activity of YwlE with the exception of the effect of oxidative stress. Herein, based on the hydrolysis of the chromogenic substrate p-nitrophenyl phosphate (pNPP) by YwlE, we investigate the role of metal cations and oxyanions in the regulation of YwlE activity. Interestingly, among the various cations that we tested, Ca2+ activates YwlE, while other cations, including Ag+, Co2+, Cd2+, and Zn2+, are inhibitory. Furthermore, as chemical analogues of phosphate, oxyanions play multiple roles in phosphatase activity. The regulatory switch Cys within the catalytic site regulates YwlE activity. Specifically, the thiol of this Cys could be alkylated by IAM (iodoacetamide) or oxidized by H2O2, resulting in enzymatic inhibition. Conversely, reducing reagents, such as DTT (dithiothreitol), β-me (β-mercaptoethanol), and TCEP (tris(2-carboxyethyl)phosphine) enhance YwlE activity. Additionally, as a stable analogue to pArg, pAIE binds to YwlE with a Kd of 149.1 nM and a binding stoichiometry n of 1.2 and inhibits YwlE with an IC50 of 316.3 ± 12.73 μM. The inhibition and activation of YwlE may have broad implications for the physiology, pharmacology and toxicology of metal cations and oxyanions.

Bio-based green solvent for the catalyst free oxidation of arylboronic acids into phenols

Gupta, Surabhi,Chaudhary, Priyanka,Seva, Lavudi,Sabiah, Shahulhameed,Kandasamy, Jeyakumar

, p. 89133 - 89138 (2015)

A bio-based green solvent, lactic acid, is found to be an efficient reaction medium for the catalyst free oxidation of arylboronic acids into phenols with aqueous hydrogen peroxide. Various substituted arylboronic acids have undergone ipso-hydroxylation smoothly at room temperature to provide corresponding phenols in excellent yields. Remarkably, the oxidation susceptible functional groups such as sulphide, ketone, aldehyde and olefin are tolerated under the reaction conditions. Over all, lactic acid showed higher efficiency as a solvent medium when compared with conventional acetic acid.

Paraoxon, 4-nitrophenyl phosphate and acetate are substrates of α- But not of β-, γ- And ζ-carbonic anhydrases

Innocenti, Alessio,Supuran, Claudiu T.

, p. 6208 - 6212 (2010)

Carbonic anhydrases (CAs, EC 4.2.1.1) belonging to α-, β-, γ- and ζ-classes and from various organisms, ranging from the bacteria, archaea to eukarya domains, were investigated for their esterase/phosphatase activity with 4-nitrophenyl acetate, 4-nitrophe

Burst kinetics and turnover in an esterase mimic

Breslow, Ronald,Nesnas, Nasri

, p. 3335 - 3338 (1999)

A catalyst combining a cyclodextrin binding group with a bound zinc cation and an oxime anion cleaves bound esters in a two step process.

Two key amino acids variant of α-l-arabinofuranosidase from bacillus subtilis str. 168 with altered activity for selective conversion ginsenoside rc to rd

Guo, Zi Yu,Luo, Zhi Yong,Tan, Shi Quan,Tian, Liang Yu,Weng, Pei,Zhang, Bian Ling,Zhang, Ru

, (2021)

α-L-arabinofuranosidase is a subfamily of glycosidases involved in the hydrolysis of L-arabinofuranosidic bonds, especially in those of the terminal non-reducing arabinofuranosyl residues of glycosides, from which efficient glycoside hydrolases can be screened for the transformation of ginsenosides. In this study, the ginsenoside Rc-hydrolyzing α-L-arabinofuranosidase gene, BsAbfA, was cloned from Bacilus subtilis, and its codons were optimized for efficient expression in E. coli BL21 (DE3). The recombinant protein BsAbfA fused with an N-terminal His-tag was overexpressed and purified, and then subjected to enzymatic characterization. Site-directed mutagenesis of BsAbfA was performed to verify the catalytic site, and the molecular mechanism of BsAbfA catalyzing ginsenoside Rc was analyzed by molecular docking, using the homology model of sequence alignment with other β-glycosidases. The results show that the purified BsAbfA had a specific activity of 32.6 U/mg. Under optimal conditions (pH 5, 40?C), the kinetic parameters Km of BsAbfA for pNP-α-Araf and gin-senoside Rc were 0.6 mM and 0.4 mM, while the Kcat /Km were 181.5 s?1 mM?1 and 197.8 s?1 mM?1, respectively. More than 90% of ginsenoside Rc could be transformed by 12 U/mL purified BsAbfA at 40?C and pH 5 in 24 h. The results of molecular docking and site-directed mutagenesis suggested that the E173 and E292 variants for BsAbfA are important in recognizing ginsenoside Rc effectively, and to make it enter the active pocket to hydrolyze the outer arabinofuranosyl moieties at C20 position. These remarkable properties and the catalytic mechanism of BsAbfA provide a good alternative for the effective biotransformation of the major ginsenoside Rc into Rd.

Ogata,Akada

, p. 15,16-18 (1972)

A mild chemoselective and rapid regeneration of alcohols from O-allyl ethers by LiCl/NaBH4

RajaRam,Purushothama Chary,Salahuddin,Iyengar

, p. 133 - 137 (2002)

An efficient chemoselective cleavage of O-allyl protected is developed employing LiCl/NaBH4.

CATALYTIC PROPERTIES OF DIMETHYL-β-CYCLODEXTRIN BEARING IMIDAZOLYLETHYL GROUP. pH DEPENDENCE AND REGIOSELECTIVITY OF THE HYDROLYSIS OF NITROPHENYL ACETATES

Ikeda, Hiroshi,Kojin, Ryoichi,Yoon, Chul-Joong,Ikeda, Tsukasa,Toda, Fujio

, p. 311 - 312 (1988)

Catalytic properties of dimethyl-β-cyclodextrin bearing imidazolylethyl group (2) were demonstrated. pKa of 2 was 7.28. (kcat)max for the hydrolysis of p-nitrophenyl acetate was 3x1E-2 s-1. 2 showed para-selectivity for the hydrolysis of nitrophenyl acetates and caused 921-fold acceleration.

Metal ion induced allosteric transition in the catalytic activity of an artificial phosphodiesterase

Takebayashi, Shinji,Ikeda, Masato,Takeuchi, Masayuki,Shinkai, Seiji

, p. 420 - 421 (2004)

An artificial phosphodiesterase (1) bearing two kinds of metal binding sites, a catalytic site and a regulatory bipyridine site showed a unique allosteric transition in the catalytic activity against the metal concentration.

Carboxy ester hydrolysis catalysed by a dinuclear, hexaazamacrocyclic zinc(II) complex. A model for zinc(II) aminopeptidases

Wendelstorf, Carsten,Warzeska, Sabine,Koevari, Endre,Kraemer, Roland

, p. 3087 - 3092 (1996)

In order to investigate a mimic of aminopeptidase enzymes a novel macrocyclic dizinc complex was prepared. A protonated form of the dinucleating hexaazamacrocycle L, [H4L][NO3]4·2H2O, was characterized by X-ray

Nitrogen Oxides and Nitric Acid Enable the Sustainable Hydroxylation and Nitrohydroxylation of Benzenes under Visible Light Irradiation

Hofmann, Laura Elena,Mach, Leonard,Heinrich, Markus R.

, p. 431 - 436 (2018)

A new type of waste recycling strategy is described in which nitrogen oxides or nitric acid are directly employed in photocatalyzed hydroxylations and nitrohydroxylations of benzenes. Through these transformations, otherwise costly denitrification can be combined with the synthesis of valuable compounds for various applications.

Enhancing catalytic performance of porcine pancreatic lipase by covalent modification using functional ionic liquids

Jia, Ru,Hu, Yi,Liu, Luo,Jiang, Ling,Zou, Bin,Huang, He

, p. 1976 - 1983 (2013)

Various functional ionic liquids (ILs) composed of different cations and anions were activated with carbonyldiimidazole and then covalently linked onto porcine pancreatic lipase (PPL) through lysine coupling. Catalytic performances, such as activity, thermostability, and enantioselectivity were improved successfully, as was investigated in p-nitrophenyl palmitate (pNPP) hydrolysis and racemic 1-phenethyl acetate hydrolysis reaction. The correlation between catalytic performance and modification of IL was studied by catalytic and spectroscopic data, which showed improvement of catalytic performances to a different extent. Hydrolytic activity was enhanced by ILs with chaotropic cations and kosmotropic anions (e.g., more than 4-fold with [choline][H 2PO4]). Modifications by ILs bearing kosmotropic cations and chaotropic anions contribute to lipase thermostability and enantioselectivity (e.g., modification with [HOOCBMIm][Cl] showed a 12-fold thermostability increase at 60 C and more than 7-fold enantioselectivity enhancement than native enzyme). The Matrix-assisted laser desorption/ ionization-time-of-flight mass spectrometry experiments suggest that ILs bind with lipase protein. Conformation changes were confirmed by fluorescence spectroscopy, and circular dichroism spectroscopy.

Polyether catalysis of ester aminolysis - A computational and experimental study

Zipse, Hendrik,Wang, Li-Hsing,Houk, Kendall N.

, p. 1511 - 1522 (1996)

Model systems for the reaction of amines with esters were investigated with ab initio methods. Ammonia and methylamine were used as models for primary amines, and formic acid, methyl acetate, phenyl acetate, and p-nitrophenyl acetate were chosen to repres

Size-tunable ZnO nanotapes as an efficient catalyst for oxidative chemoselective C–B bond cleavage of arylboronic acids

Phukan, Shreemoyee,Mahanta, Abhijit,Rashid, Md. Harunar

, p. 58 - 66 (2018)

Herein, we report a simple but effective chemical approach for the synthesis of size-tunable ZnO nanotapes by precipitation method in the presence of phytochemicals present in the flower extract of Lantana camara plant. The electron microscopic study confirmed that the size of ZnO nanotapes can be systematically controlled by varying the concentration of either flower extract or metal ions and the flower extract played the key role in controlling the growth of ZnO nanotapes. The phase and crystalline analysis was carried out by X-ray diffraction method which indicated that ZnO nanostructures are highly crystalline in nature and are free from any impurities. The synthesized ZnO nanostructures exhibited interesting optical properties as investigated by UV–vis absorption and photoluminescence spectroscopy. Further the surface functionalities affect the optical properties of ZnO nanostructures which possess relatively strong UV emissions; a blue emission and a green emission. The synthesized ZnO nanostructures showed excellent catalytic properties in the ipso-hydroxylation of different aryl/ hetero-arylboronic acid to phenol in a relatively greener reaction conditions. These catalysts are highly stable and are re-usable upto six cycles of ipso-hydroxylation without losing its catalytic properties.

The development of a Cu(I)/pyrazolylpyridineamine catalyst system for the hydroxylation of aryl halides

Marais, Lindie,Vosloo, Hermanus C.M.,Swarts, Andrew J.

, (2020)

A catalyst system comprising of pyrazolylpyridineamine/Cu(I)/CsOH is reported. for the hydroxylation of aryl iodides and bromides with moderate to outstanding yields, without the use of an inert atmosphere. A comprehensive parameter optimisation study established optimum component concentrations: [Cu(MeCN)4]BF4 and 2-(1H-pyrazol-1-yl)-N-(pyridine-2-ylmethyl)ethan-1-amine (L01) (2 mol %), substrate (1 mmol), CsOH (4 mmol) and DMSO:H2O (1:1, 3 mL). Monitoring substrate conversion as a function of time revealed an induction period of 90 min, which could be eliminated through the initial in situ formation of the proposed [(L01)Cu-OH] intermediate. Eliminating the induction period resulted in complete conversion within one hour, with turnover numbers exceeding that of the benchmark catalyst system operating at an optimal catalyst loading of 0.05 mol %.

Silica-acetate complex of N2O4: A heterogeneous reagent for the selective nitration of phenols and nitrosation of thiols

Iranpoor,Firouzabadi,Heydari

, p. 703 - 710 (2003)

Complexation of gaseous N2O4 with acylated silica gel affords an addition compound, which is an efficient heterogeneous reagent for the selective mono- and dinitration of phenol, substituted phenols and nitrosation of thiols.

ISOLATION OF β-N-ACETYL-D-HEXOSAMINIDASES FROM LUPIN SEED

Farlane, Ernest F. Mc,Farlane, Dallas R. Mc,Kennedy, Ivan R.

, p. 2431 - 2434 (1984)

A rapid procedure for the isolation of β-N-acetyl-D-hexosiminidase from lupin seed meal is described.This involves affinity chromatography of a seed extract on concanavalin A, followed by chromatography on DEAE-Sepharose.The purified enzyme was obatined i

Cloning, expression, purification, and characterization of a thermostable esterase from the archaeon Sulfolobus solfataricus P1

Nam, Jae-Kyung,Park, Young-Jun,Lee, Hee-Bong

, p. 95 - 103 (2013)

A genomic library of the thermoacidophilic archaeon Sulfolobus solfataricus P1 was constructed using 3.5 kb BamHI-fragments into pUC118 vector and the recombinant plasmids were hosted in Escherichia coli. One positive clone showing thermostable esterase a

Mild and rapid hydroxylation of aryl/heteroaryl boronic acids and boronate esters with N-oxides

Zhu, Chen,Wang, Rui,Falck

, p. 3494 - 3497 (2012)

Aryl and heteroaryl boronic acids and boronate esters are rapidly, often within minutes, transformed into the corresponding phenols by N-oxides in an open flask at ambient temperature. This transformation has broad compatibility with a variety of functional groups.

1,3,4-Oxadiazole-2(3H)-thione and its analogues: A new class of non-competitive nucleotide pyrophosphatases/phosphodiesterases 1 inhibitors

Khan, Khalid M.,Fatima, Naheed,Rasheed, Maimona,Jalil, Saima,Ambreen, Nida,Perveen, Shahnaz,Choudhary, M. Iqbal

, p. 7816 - 7822 (2009)

A series of 1,3,4-oxadiazole-2 (3H)-thiones and 1,3,4-thiadiazole-2 (3H)-thiones were synthesized and evaluated for their inhibitory activities against the two nucleotide pyrophosphatase phosphodiesterase 1 enzymes. Dixon, as well as Lineweaver-Burk plots

Self-Assembled Peptide Nano-Superstructure towards Enzyme Mimicking Hydrolysis

Chen, Yu,Dong, Hao,Gazit, Ehud,Haimov, Elvira,Ju, Meiting,Makam, Pandeeswar,Orr, Asuka A.,Redko, Boris,Rencus-Lazar, Sigal,Shimon, Linda J. W.,Tamamis, Phanourios,Wang, Yannan,Yang, Yuqin

, p. 17164 - 17170 (2021)

The structural arrangement of amino acid residues in native enzymes underlies their remarkable catalytic properties, thus providing a notable point of reference for designing potent yet simple biomimetic catalysts. Herein, we describe a minimalistic appro

A β-D-FUCOSIDASE FROM ASCLEPIAS CURASSAVICA LATEX

Giordani, Roger,Lafon, Laurence

, p. 1327 - 1332 (1993)

A β-D fucosidase was isolated from Asclepias curassavica latex by anion exchange and gel filtration chromatography.The enzyme was purified 136-fold.The enzyme is a monomer and its Mr is close to 50000.It shows optimal activity at pH 5.5 and at

SbCl5-wet acetonitrile: A new system for chemoselective O-desilylation

Glória, Paulo M. C.,Prabhakar, Sundaresan,Lobo, Ana M.,Gomes, Mário J. S.

, p. 8819 - 8821 (2003)

A new efficient method for deprotection of TBDMS derivatives of phenols, primary alcohols, carboxylic acids and secondary amines, consisting of SbCl 5 and MeCN with 0.1% water (w/v), is reported. It effects inter alia desilylation of a CH2OTBDMS group in the presence of a ketal function.

Synthesis of short chain alkyl esters using cutinase from Burkholderia cepacia NRRL B2320

Dutta, Kasturi,Dasu, Veeranki Venkata

, p. 150 - 156 (2011)

Short chain alkyl esters are well appreciated for fruity flavors they provide. These are mainly applied to the fruit-flavored products like jam, jelly, beverages, wine and dairy. Cutinase from Burkholderia cepacia NRRL B 2320 was found to be active in catalyzing the synthesis of alkyl esters in organic solvent. The optimal temperature range for the enzyme catalyzed synthesis was found to be from 35 °C to 40 °C. The maximum conversion (%) during synthesis of ester was obtained for butyric acid (C4) and valeric acid (C5) with butanol reflecting the specificity of the enzyme for short-chain length fatty acids. In case of alcohol specificity, butanol was found to be most preferred substrate by the enzyme and conversion (%) decreased with increasing carbon chain length of alcohol used in the esterification reaction. The kinetic analysis for the synthesis of butyl butyrate by varying concentration of one substrate at a time (butanol or butyric acid), showed that Ping-Pong Bi Bi model with acid inhibition and influence of initial water is most suitable model for the prediction of the reaction kinetics.

Galactofuranosidase from JHA 19 Streptomyces sp.: subcloning and biochemical characterization

Seni?ar, Mateja,Legentil, Laurent,Ferrières, Vincent,Eliseeva, Svetlana V.,Petoud, Stéphane,Takegawa, Kaoru,Lafite, Pierre,Daniellou, Richard

, p. 35 - 41 (2019)

Despite the crucial role of the rare galactofuranose (Galf) in many pathogenic micro-organisms and our increased knowledge of its metabolism, there is still a lack of recombinant and efficient galactofuranoside hydrolase available for chemo-enzymatic synthetic purposes of specific galactofuranosyl-conjugates. Subcloning of the Galf-ase from JHA 19 Streptomyces sp. and its further overexpression lead us to the production of this enzyme with a yield of 0.5 mg/L of culture. It exhibits substrate specificity exclusively towards pNP β-D-Galf, giving a KM value of 250 μM, and the highest enzymatic efficiency ever observed of 14 mM?1 s?1. It proved to be stable to temperature up to 60 °C and to at least 4 freeze-thaw's cycles. Thus, Galf-ase demonstrated to be an efficient and stable biocatalyst with greatly improved specificity toward the galactofuranosyl entity, thus paving the way to the further development of transglycosylation and thioligation reactions.

Paraoxonase Mimic by a Nanoreactor Aggregate Containing Benzimidazolium Calix and l-Histidine: Demonstration of the Acetylcholine Esterase Activity

Singh, Amanpreet,Saini, Sanjeev,Mayank,Kaur, Navneet,Singh, Ajnesh,Singh, Narinder,Jang, Doo Ok

, p. 5737 - 5744 (2021)

An anion-mediated preorganization approach was used to design and synthesize the benzimidazolium-based calix compound R1?2 ClO4?. X-ray crystallography analysis revealed that the hydrogen-bonding interactions between the benzimidazol

X-ray crystallographic analysis of the 6-aminohexanoate cyclic dimer hydrolase: Catalytic mechanism and evolution of an enzyme responsible for nylon-6 byproduct degradation

Yasuhira, Kengo,Shibata, Naoki,Mongami, Go,Uedo, Yuki,Atsumi, Yu,Kawashima, Yasuyuki,Hibino, Atsushi,Tanaka, Yusuke,Lee, Young-Ho,Kato, Dai-Ichiro,Takeo, Masahiro,Higuchi, Yoshiki,Negoro, Seiji

, p. 1239 - 1248 (2010)

We performed x-ray crystallographic analyses of the 6-aminohexanoate cyclic dimer (Acd) hydrolase (NylA) from Arthrobacter sp., an enzyme responsible for the degradation of the nylon-6 industry byproduct. The fold adopted by the 472-amino acid polypeptide generated a compact mixed α/β fold, typically found in the amidase signature superfamily; this fold was especially similar to the fold of glutamyl-tRNAGln amido-transferase subunit A (z score, 49.4) and malonamidase E2 (z score, 44.8). Irrespective of the high degree of structural similarity to the typical amidase signature superfamily enzymes, the specific activity of NylA for glutamine, malonamide, and indoleacetamide was found to be lower than 0.5% of that for Acd. However, NylA possessed carboxylesterase activity nearly equivalent to the Acd hydrolytic activity. Structural analysis of the inactive complex between the activity-deficient S174A mutant of NylA and Acd, performed at 1.8 A resolution, suggested the following enzyme/substrate interactions: a Ser174-cis-Ser150-Lys72 triad constitutes the catalytic center; the backbone N in Ala171 and Ala172 are involved in oxyanion stabilization; Cys316-Sγ forms a hydrogen bond with nitrogen (Acd-N7) at the uncleaved amide bond in two equivalent amide bonds of Acd. A single S174A, S150A, or K72A substitution in NylA by site-directed mutagenesis decreased the Acd hydrolytic and esterolytic activities to undetectable levels, indicating that Ser174-cis-Ser150-Lys72 is essential for catalysis. In contrast, substitutions at position 316 specifically affected Acd hydrolytic activity, suggesting that Cys316 is responsible for Acd binding. On the basis of the structure and functional analysis, we discussed the catalytic mechanisms and evolution of NylA in comparison with other Ser-reactive hydrolases.

Hydrolysis of Some Chromogenic Substrates and Adenosine Triphosphate Catalyzed by Phosphodiesterase-phosphomonoesterase from Fusarium moniliforme

Yoshida, Hiroshi,Kawai, Masayuki,Okimura, Chiseko,Hirama, Nobuyuki,Konno, Osamu

, p. 549 - 553 (1983)

For comparison with known phosphodiesterases, the mode of action of phosphodiesterase-phosphomonoesterase from Fusarium moniliforme toward some key substrates was examined.The enzyme catalyzed the hydrolysis of either thymidine 3'-(4-nitrophenylphosphate)

Photocatalytic Molecular Oxygen Activation by Regulating Excitonic Effects in Covalent Organic Frameworks

Qian, Yunyang,Li, Dandan,Han, Yulan,Jiang, Hai-Long

, p. 20763 - 20771 (2020)

Excitonic effects caused by Coulomb interactions between electrons and holes play subtle and significant roles on photocatalysis, yet have been long ignored. Herein, porphyrinic covalent organic frameworks (COFs, specifically DhaTph-M), in the absence or presence of different metals in porphyrin centers, have been shown as ideal models to regulate excitonic effects. Remarkably, the incorporation of Zn2+ in the COF facilitates the conversion of singlet to triplet excitons, whereas the Ni2+ introduction promotes the dissociation of excitons to hot carriers under photoexcitation. Accordingly, the discriminative excitonic behavior of DhaTph-Zn and DhaTph-Ni enables the activation of O2 to 1O2 and O2?-, respectively, under visible light irradiation, resulting in distinctly different activity and selectivity in photocatalytic terpinene oxidation. Benefiting from these results, DhaTph-Ni exhibits excellent photocatalytic activity in O2?-engaged hydroxylation of boronic acid, while DhaTph-Zn possesses superior performance in 1O2-mediated selective oxidation of organic sulfides. This work provides in-depth insights into molecular oxygen activation and opens an avenue to the regulation of excitonic effects based on COFs.

Di and tetranuclear Cu(II) complexes with simple 2-aminoethylpyridine: Magnetic properties, phosphodiester hydrolysis, DNA binding/cleavage, cytotoxicity and catecholase activity

Sureshbabu, Popuri,Junaid, Qazi Mohammad,Upadhyay,Victoria,Pitchavel, Vidhyapriya,Natarajan, Sakthivel,Sabiah

, p. 202 - 218 (2019)

Di and tetranuclear Cu(II) complexes, [Cu2(2-AEP)4(μ-Cl)](ClO4)3 (1) and [Cu4(μ3-OH)2(μ2-OH)2(2-AEP)4(μ2-ClO4)2]

Kinetic and crystallographic analyses of the catalytic domain of chitinase from Pyrococcus furiosus- the role of conserved residues in the active site

Tsuji, Hiroaki,Nishimura, Shigenori,Inui, Takashi,Kado, Yuji,Ishikawa, Kazuhiko,Nakamura, Tsutomu,Uegaki, Koichi

, p. 2683 - 2695 (2010)

The hyperthermostable chitinase from the hyperthermophilic archaeon Pyrococcus furiosus has a unique multidomain structure containing two chitin-binding domains and two catalytic domains, and exhibits strong crystalline chitin hydrolyzing activity at high

Efficient chemoenzymatic synthesis of 4-nitrophenyl β-d-apiofuranoside and its use in screening of β-d-apiofuranosidases

Kis, Peter,Potocká, Elena,Mastihuba, Vladimír,Mastihubová, Mária

, p. 48 - 53 (2016)

4-Nitrophenyl β-d-apiofuranoside as a chromogenic probe for detection of β-d-apiofuranosidase activity was prepared in 61% yield from 2,3-isopropylidene-α,β-d-apiofuranose through a sequence of five reactions. The synthesis involves one regioselective enz

A novel extracellular cold-active esterase of Pseudomonas sp. TB11 from glacier No.1: Differential induction, purification and characterisation

Dong, Juan,Zhao, Wei,Gasmalla, Mohammed A.A.,Sun, Jingtao,Hua, Xiao,Zhang, Wenbin,Han, Liang,Fan, Yuting,Feng, Yinghui,Shen, Qiuyun,Yang, Ruijin

, p. 53 - 63 (2015)

The production, purification, characterization and application of a novel cold active esterase by Pseudomonas sp. TB11 are described herein. A new finding regarding the production of extracellular esterase activity depending upon single cream as an induce

Metallomicelles as Catalysts of the Hydrolysis of Carboxylic and Phosphoric Acid Esters

Scrimin, Paolo,Tecilla, Paolo,Tonellato, Umberto

, p. 161 - 166 (1991)

Lipophilic ligands 2-4 have been synthesized.In the presence of Cu(II) ions, they form metallomicelles that are catalytically active in the cleavage of the p-nitrophenyl esters of acetic, hexanoic, and dodecanoic acids.Catalysis was also observed in the cleavage of p-nitrophenyl diphenyl phosphate.The apparent pKa of the Cu(II)-coordinated hydroxyl of ligand 2a, in the micellar aggregate, is 7.7, as estimated from the rate vs pH profiles for both classes of esters: this suggests that the hydroxyl is involved as a nucleophile in the hydrolytic cleavage, which proved to be a really catalytic process.The ligand bearing the free hydroxyl (2a) is more effective in the cleavage of carboxylate esters than ligands with the methylated alcoholic group (2b) or devoid of it (4); the opposite behaviour is observed in the cleavage of the phosphate triester.A rationale is offered that calls for the difference in the coordination ability to the metal center of phosphate and carboxylate esters.

Can Acyl Transfer Occur via a Concerted Mechanism ? Direct Evidence from Heavy-Atom Isotope Effects

Hengge, Alvan

, p. 6575 - 6576 (1992)

-

Questioning the paradigm of metal complex promoted phosphodiester hydrolysis: [Mo7O24]6- polyoxometalate cluster as an unlikely catalyst for the hydrolysis of a DNA model substrate

Cartuyvels, Els,Absillis, Gregory,Parac-Vogt, Tatjana N.

, p. 85 - 87 (2008)

The first example of a phosphodiester bond cleavage promoted by a highly negatively charged polyoxometalate cluster has been discovered: the hydrolysis of the phosphodiester bond in a DNA model substrate bis(p-nitrophenyl)phosphate (BNPP) is promoted by t

Significantly enhanced photocatalytic performance of In2O3 hollow spheres: via the coating effect of an N,S-codoped carbon layer

Sun, Liming,Yuan, Yusheng,Li, Rong,Zhan, Wenwen,Wang, Xiao-Jun,Zhao, Yanli,Han, Xiguang

, p. 25423 - 25432 (2019)

A typical catalytic process generally consists of diffusion, adsorption and surface reaction, which should be fully taken into account for the catalyst design. In this article, we synthesized hollow spheres (N,S-C/In2O3 HSs) assembled from N,S-codoped carbon layer coated In2O3 nanoparticles, in which the porous architecture could provide diffusion channels for reactant molecules, the N,S-codoped carbon layer could enhance the separation efficiency of photogenerated carriers, and the hollow structure could improve the amount of active sites and enhance the light utilization efficiency. The obtained N,S-C/In2O3 HS exhibits extraordinary photocatalytic oxidative hydroxylation of arylboronic acids under blue-light irradiation. From the theoretical calculations, it was found that the carbon layer not only strengthens the adsorption of arylboronic acid reactants, but also activates the boron atom in arylboronic acids. The present work indicates that the carbon layer could be used as a medium between inorganic semiconductor photocatalysts and organic reactant molecules, thus promoting the application scope of inorganic semiconductor photocatalysts in the field of selective organic synthesis.

Catalytic properties of diblock copolymers of N-vinylcaprolactam and N-vinylimidazole

Barabanova,Blagodatskikh,Vyshivannaya,Klimova,Grinberg,Burova,Muranov,Lozinskii,Grinberg,Peregudov,Khokhlov

, p. 253 - 256 (2015)

Thermoresponsive diblock copolymers of N-vinylcaprolactam (VCL) with N-vinylimidazole (NVI) have been synthesized for the first time through two-stage controlled reversible addition-fragmentation chain transfer (RAFT) polymerization. The resulting diblock

The lipase/lipoxygenase bienzyme system in AOT reversed micelles in octane

Pavlenko,Kuptsova,Klyachko,Levashov

, p. 44 - 49 (2002)

In this work it is shown that the bienzyme lipase/lipoxygenase system can function in reversed micelles of bis(2-ethyl)hexyl sulfosuccinate (AOT) in octane. As a lipase substrate, a fish fat preparation (fat of sea mammals) with a high content of polyunsa

Metallomicelle catalysis: Hydrolysis of p-nitrophenyl picolinate induced by schiff base Co(II) complexes in a gemini surfactant micellar solution

Jiang, Weidong,Xu, Bin,Li, Jianzhang,Lin,Zeng, Xiancheng,Chen, Hua

, p. 672 - 680 (2007)

Two Schiff base cobalt(II) complexes containing crowned substituents have been synthesized and employed to promote the hydrolysis of p-nitrophenyl picolinate (PNPP) in a buffered micellar solution formed by a cationic Gemini surfactant, bis(hexadecyldimet

A single amino acid residue determines the ratio of hydrolysis to transglycosylation catalyzed by β-glucosidases

Frutuoso,Marana

, p. 102 - 106 (2013)

The propensity to catalysis of transglycosylation of the β-glucosidase Tmβgly is higher than for Sfβgly. Moreover the propensity to catalysis of transglycosylation is directly proportional to the substrate concentration for Tmβgly, whereas for Sfβgly it is constant. For instance, 60% of a Tmβgly sample catalyzes transglycosylation reactions at 40 mM p-nitrophenyl β-glucoside, whereas only 40% is engaged in hydrolysis of this substrate. For Sfβgly the fraction involved in transglycosylation is only 30 %. In addition, 48 % of a Tmβgly sample catalyzes transglycosylation reactions at 8 mM methylumbelliferyl β-glucoside, whereas Sfβgly does not catalyze transglycosylation using this substrate. Interestingly, these Tmβgly properties were grafted into Sfβgly by a single replacement of a residue forming a channel involved in supplying the catalytic water molecules for attack on the covalent intermediate present in the reaction catalyzed by β-glucosidases. Hence a single residue determines the ratio of hydrolysis to transglycosylation reactions catalyzed by these β-glucosidases.

Molecular engineering of organophosphate hydrolysis activity from a weak promiscuous lactonase template

Meier, Monika M.,Rajendran, Chitra,Malisi, Christoph,Fox, Nicholas G.,Xu, Chengfu,Schlee, Sandra,Barondeau, David P.,Hoecker, Birte,Sterner, Reinhard,Raushel, Frank M.

, p. 11670 - 11677 (2013)

Rapid evolution of enzymes provides unique molecular insights into the remarkable adaptability of proteins and helps to elucidate the relationship between amino acid sequence, structure, and function. We interrogated the evolution of the phosphotriesteras

Reactivity of α-amino acids in the N-acylation with benzoic acid esters in aqueous dioxane

Ishkulova,Oparina,Kochetova,Kustova,Kalinina,Kuritsin

, p. 964 - 967 (2010)

The effect of the nitro group as a substituent in the phenoxide part of phenyl benzoate on the rate of N-acylation of glycine, L-proline,and L-valine in the water (40 wt %)-dioxane solvent was studied. The activation parameters of glycine reactions with the esters were measured. The existence of compensation effect and the linear relation of the logarithms of the acylation constants to the Hammett constants were revealed. The energy of the LUMO of esters can serve as the descriptors of the easters reactivity. Pleiades Publishing, Ltd., 2010.

Diffusion-Controllable Biomineralization Conducted in Situ in Hydrogels Based on Reversibly Cross-Linked Hyperbranched Polyglycidol

Gosecki, Mateusz,Kazmierski, Slawomir,Gosecka, Monika

, p. 3418 - 3431 (2017)

We present biocompatible hydrogel systems suitable for biomineralization processes based on hyperbranched polyglycidol cross-linked with acrylamide copolymer bearing carbonyl-coordinated boronic acid. At neutral pH, diol functional groups of HbPGL react w

Effects of Pressure on Hydrolysis of p-Nitrophenyl Acetate in Aerosol OT Reversed Micelles

Tamura, Katsuhiro,Yoshinari, Mami

, p. 2073 - 2075 (1989)

Kinetic studies were mad on imidazole-catalyzed hydrolysis of p-nitrophenyl acetate in Aerosol OT (AOT) reversed micelles (AOT/H2O/heptane) at high pressure.The rate of the reaction was found to increase with increase in the size of the aqueous core in th

A remarkable rate-accelerating metal ion effect on the intramolecular transesterification reaction of a phosphodiester in acetonitrile

Kondo, Shin-Ichi,Yoshida, Kitaro,Yano, Yumihiko

, p. 106 - 107 (1999)

The intramolecular transesterification reaction of 2-hydroxypropyl 4- nitrophenyl phosphate is greatly accelerated (105-106 fold) by the addition of divalent metal ions such as Zn2+ and Cu2+ in MeCN without a ba

Processing of soybean products by semipurified plant and microbial α-galactosidases

Falkoski, Daniel L.,Guimaraes, Valeria M.,Callegari, Carina M.,Reis, Angelica P.,De Barros, Everaldo G.,De Rezende, Sebastiao T.

, p. 10184 - 10190 (2006)

Galactooligosaccharides (GO) are responsible for intestinal disturbances following ingestion of legume-derived products. Enzymatic reduction of GO level in these products is highly desirable to improve their acceptance. For this purpose, plant and microbial semipurified α-galactosidases were used for GO hydrolysis in soybean flour and soy molasses. α-Galactosidases from soybean germinating seeds, Aspergillus terreus, and Penicillium griseoroseum presented maximal activities at pH 4.0-5.0 and 45-65°C. The K M,app values determined for raffinose by the soybean, A. terreus, and P. griseoroseum α-galactosidases were 3.44, 19.39, and 20.67 mM, respectively. The enzymes were completely inhibited by Ag+ and Hg2+, whereas only soybean enzyme was inhibited by galactose. A. terreus α-galactosidase was more thermostable than the enzymes from the other two sources. This enzyme maintained about 100% of its original activity after 3 h at 60°C. The microbial a-galactosidases were more efficient for reducing GO in soybean flour and soy molasses than soybean enzyme.

Friedburg, L. H.,Mandel, J. A.

, p. 7 (1890)

Immobilization of a novel cold active esterase onto Fe3O4~cellulose nano-composite enhances catalytic properties

Rahman, Mohammad Asadur,Culsum, Umma,Kumar, Ashok,Gao, Haofeng,Hu, Nan

, p. 488 - 497 (2016)

A novel esterase, EstH was cloned, purified and characterized from the marine bacterium Zunongwangia sp. The purified EstH showed optimum activity at 30 °C and pH 8.5 with ~50% of original activity at 0 °C. EstH was stable in high salt conditions (0-4.5 M

Copper(II) complexes of N-methylated derivatives of ortho- and meta-xylyl-bridged bis(1,4,7-triazacyclononane) ligands: Synthesis, X-ray structure and reactivity as artificial nucleases

Belousoff, Matthew J.,Graham, Bim,Spiccia, Leone

, p. 4133 - 4139 (2008)

Two new binucleating ligands, 1,3-bis[(4,7-dimethyl-1,4,7-triazacyclononan- 1-yl)methyl]benzene (Lmemx) and 1,2-bis-[(4,7-dimethyl-1,4,7- triazacyclononan-1-yl)methyl]benzene (Lmeox), have been prepared from 1,4,7-triazatricyclo-[5.2

A minimalist approach to understanding the efficiency of mononuclear Zn(ii) complexes as catalysts of cleavage of an RNA analog

Mathews, Ryan A.,Rossiter, Clifford S.,Morrow, Janet R.,Richard, John P.

, p. 3804 - 3811 (2007)

Mononuclear complexes between Zn2+ and the following four macrocycles were prepared: 1,4,7,10-tetraazacyclododecane (1), 1-oxa-4,7,10-triazacyclododecane (2), 1,5,9-triazacyclododecane (3) and 1-hydroxyethyl-1,4,7-triazacyclononane (4). The pH

Copper(II) and Zinc(II) Complexes of Conformationally Constrained Polyazamacrocycles as Efficient Catalysts for RNA Model Substrate Cleavage in Aqueous Solution at Physiological pH

Bím, Daniel,Svobodová, Eva,Eigner, Václav,Rulí?ek, Lubomír,Hoda?ová, Jana

, p. 10426 - 10437 (2016)

As part of a quest for efficient artificial catalysts of RNA phosphodiester bond cleavage, conformationally constrained mono- and bis-polyazamacrocycles in which tri- or tetraazaalkane chains link the ortho positions of a benzene ring were synthesized. The catalytic activities of mono- and dinuclear copper(II) and zinc(II) complexes of these polyazamacrocycles towards cleavage of the P?O bond in 2-hydroxypropyl-4-nitrophenylphosphate (HPNP) in aqueous solution at pH 7 have been determined. Only the complexes of the ligands incorporating three nitrogen atoms in a macrocycle proved to be capable of efficiently catalyzing HPNP transesterification. The dinuclear complexes were found to be approximately twice as efficient as their mononuclear counterparts, and exhibited Michaelis–Menten saturation kinetics with calculated rate constants of kcat≈10?4s?1. By means of quantum chemical calculations (DFT/COSMO-RS), several plausible reaction coordinates were described. By correlating the calculated barriers with the experimental kinetic data, two possible reaction scenarios were revealed, with activation free energies of 20–25 kcal mol?1.

Exploring the catalytic mechanism of a novel β-glucosidase BGL0224 from Oenococcus oeni SD-2a: Kinetics, spectroscopic and molecular simulation

Zhang, Jie,Zhao, Ning,Xu, Junnan,Qi, Yiman,Wei, Xinyuan,Fan, Mingtao

, (2021)

The β-glucosidase derived from microorganisms has attracted worldwide interest for their industrial applications, but studies on β-glucosidases from Oenococcus oeni are rare. In this paper, catalytic mechanism of a novel β-glucosidase BGL0224 of Oenococcu

A Dual-Function Highly Crystalline Covalent Organic Framework for HCl Sensing and Visible-Light Heterogeneous Photocatalysis

Addicoat, Matthew A.,Nailwal, Yogendra,Pal, Santanu Kumar,Wonanke, A. D. Dinga

, p. 6595 - 6604 (2021)

Covalent organic frameworks (COFs) offer great potential for various advanced applications such as photocatalysis, sensing, and so on because of their fully conjugated, porous, and chemically stable unique structural architecture. In this work, we have designed and developed a truxene-based ultrastable COF (Tx-COF-2) by Schiff-base condensation between 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 5,5,10,10,15,15-hexamethyl-10,15-dihydro-5H-diindeno(1,2-a:1′,2′-c)fluorene-2,7,12-tricarbaldehyde (Tx-CHO) for the first time. The resulting COF possesses excellent crystallinity, permanent porosity, and high Brunauer-Emmett-Teller (BET) surface areas (up to 1137 m2 g-1). The COF was found to be a heterogeneous, recyclable photocatalyst for efficient conversion of arylboronic acids to phenols under visible-light irradiation, an environmentally friendly alternative approach to conventional metal-based photocatalysis. Besides, Tx-COF-2 provides an immediate naked-eye color change (1 s) and fluorescence "turn-on"phenomena upon exposure to HCl. The response is highly sensitive, with an ultralow detection limit of up to 4.5 nmol L-1.

-

Merz,Waters

, p. 2427,2428, 2432 (1949)

-

Investigation of a general base mechanism for ester hydrolysis in C-C hydrolase enzymes of the α/β-hydrolase superfamily: A novel mechanism for the serine catalytic triad

Li, Jian-Jun,Bugg, Timothy D. H.

, p. 507 - 513 (2007)

Previous mechanistic and crystallographic studies on two C-C hydrolase enzymes, Escherichia coli MhpC and Burkholderia xenovorans BphD, support a general base mechanism for C-C hydrolytic cleavage, rather than the nucleophilic mechanism expected for a ser

High paraoxon-hydrolyzing activity in organophosphorous insecticide-resistant mosquitoes

Watanabe,Takebe,Kobashi

, p. 980 - 985 (1991)

We found a strong paraoxon-hydrolyzing activity (23.4±8.50 nmol/h/individual and 137±86.2 nmol/h/mg protein) in the crude extract from larvae of Culex tritaeniorhynchus Toyama 89, which is markedly resistant to organophosphorous insecticides. The activity

A photoresponsive glycosidase mimic

Samanta, Mousumi,Siva Rama Krishna,Bandyopadhyay, Subhajit

, p. 10577 - 10579 (2014)

Azobenzene-3,3′-dicarboxylic acid exists in photoisomerizable (E) and (Z)-forms. Deprotonation of the carboxylic acid groups from the (E)-form occurs simultaneously, whereas in the (Z)-form it occurs in a stepwise fashion. The mono anionic form of the (Z)

A simple and practical copper-catalyzed approach to substituted phenols from aryl halides by using water as the solvent

Yang, Daoshan,Fu, Hua

, p. 2366 - 2370 (2010)

Water surprise! A simple and practical copper-catalyzed approach to substituted phenols by hydroxylation of aryl halides has been developed by using environmentally benign water as the solvent (see scheme). The method proceeds under mild conditions and is tolerant towards various functional groups in the substrates.

Antibody-catalyzed formation of a 14-membered ring lactone

Pungente, Michael D.,Weiler, Larry,Ziltener, Hermann J.

, p. 1643 - 1645 (2002)

Monoclonal antibody (MAb) F123, raised against a macrocyclic phosphonate transition-state analogue, catalyzed an intramolecular transesterification of the corresponding hydroxy ester to give a 14-membered ring lactone. The MAb reaction displayed enzyme-like Michaelis-Menten kinetics with a Km of 255 μM and a kcat of 0.01 min-1 based on p-nitrophenol release and calculated on an active-site basis. Substrate specificity and competitive inhibition by a transition state analogue (Ki = 3 μM) demonstrated that the catalytic activity was associated with binding in the anti-body-combining site. The lactone product was isolated from a large-scale catalytic experiment through ether extraction and identified by gas chromatography - mass spectroscopy.

Inclusion effects of cyclomaltohexa- and heptaose (α- and β-cyclodextrins) on the acidities of several phenol derivatives

Hamai, Sanyo,Satoh, Noriko

, p. 229 - 237 (1997)

By means of spectrophotometry, equilibrium constants for the formation of 1:1 inclusion complexes of cyclomaltohexaose (α-cyclodextrin, α-CD) or cyclomaltoheptaose (β-CD) in aqueous solutions have been evaluated for neutral and anionic species of 3-cyanophenol, 4-cyanophenol, 3-nitrophenol, 4-nitrophenol, 4-bromophenol, and 4-methoxyphenol. Using the equilibrium constants of the neutral and anionic species, pK(a) values have been determined for the phenols bound to the α- and β-CD cavities. These phenols, which are accommodated in the α-CD cavity, have been found to be stronger acids than the free, uncomplexed ones, except for 4-methoxyphenol. On the other hand, 4-cyanophenol, 3-nitrophenol, and 4-methoxyphenol bound to the β-CD cavity are weaker acids than the uncomplexed ones, although,3-cyanophenol, 3-nitrophenol, and 3-bromophenol bound to β-CD show the same trend as those bound to α-CD. The different influences of α- and β-CDs on the pK(a) values are likely due to the difference in the magnitudes of the induced dipole moments of the guest caused by α- and β-CDs; depending on the magnitude of the induced dipole moment, the inclusion complexes are stabilized through the dipole-dipole interaction between the host and guest.

Kinetics and mechanism of the aminolysis of 4-methylphenyl and 4-chlorophenyl 4-nitrophenyl carbonates in aqueous ethanol

Castro, Enrique A.,Andujar, Monica,Toro, Alejandra,Santos, Jose G.

, p. 3608 - 3613 (2003)

Reactions of 4-methylphenyl 4-nitrophenyl carbonate (MPNPC) and 4-chlorophenyl 4-nitrophenyl carbonate (CIPNPC) with a series of quinuclidines (QUIN) and the latter carbonate with a series of secondary alicyclic amines (SAA) are subjected to a kinetic investigation in 44 wt % ethanol-water, at 25.0°C and an ionic strength of 0.2 M. The reactions were followed spectrophotometrically at 330 or 400 nm (4-nitrophenol or 4-nitrophenoxide anion appearance, respectively). Under excess amine, pseudo-first-order rate coefficients (kobsd) are found. For all these reactions, plots of kobsd vs free amine concentration at constant pH are linear, the slope (kN) being independent of pH. The Broensted-type plots (log kN vs pKa of the conjugate acids of the amines) for the reactions of the series of QUIN with MPNPC and ClPNPC are linear with slopes (βN) 0.88 and 0.87, respectively, which are explained by a stepwise process where breakdown of a zwitterionic tetrahedral intermediate (T±) to products is rate limiting. The Broensted-type plot for the reactions of the series of SAA with ClPNPC is biphasic with slopes β1 = 0.2 (high pKa region) and β2 = 0.9 (low pKa region) and a curvature center at pKa0 = 10.6. This plot is in accordance with a stepwise mechanism through T± and a change in the rate-determining step, from T± breakdown to T± formation as the basicity of the SAA increases. Two conclusions arise from these results: (i) QUIN are better leaving groups from T± than isobasic SAA, and (ii) the nonleaving group effect on kN for these reactions is small, since βnlg ranges from -0.2 to - 0.3. From these values, it is deduced that ClPNPC is ca. 70% more reactive than MPNPC toward SAA and QUIN, when expulsion of the leaving group from T± is the rate determining step.

Ionic complex of N2O4 with 18-crown-6: A highly efficient and selective reagent for nitration of phenols

Iranpoor,Firouzabadi,Heydari

, p. 3295 - 3302 (1999)

Interaction of gaseous N2O4 with 18-crown-6 affords the stable crystalline complex of NO+ · 18-crown-6 · H(NO3)2· This ionic complex is an efficient nitrating agent for the selective mono-, di-, and trinitration of phenol and also for the selective mono-, and dinitration of substituted phenols.

Comparative evaluation of D-glucosyl thiouronium, glucosylthio heterocycles, Daonil, and insulin as inhibitors for hepatic glycosidases

El Din Awad, Olfat M.,Attia, Wafaa E.,El Ashry, El Sayed H.

, p. 469 - 476 (2004)

Comparison of the in vivo and in vitro effects of S-(2,3,4,6-tetra-O- acetyl-β-D-glucopyranosyl)thiuronium bromide (1), 2-(2,3,4,6-tetra-O- acetyl-β-D-glucopyranosylthio-1,3,4-thiadiazolin-5-thione (2), and 2-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosylthio

β-D-GLUCOSIDASES OF SCLEROTIUM ROLFSII. SUBSTRATE SPECIFICITY AND MODE OF ACTION

Sadana, Jai C.,Shewale, Jaiprakash G.,Patil, Rajukmar V.

, p. 205 - 214 (1983)

The substrate specificity and mode of action of the four pure β-D-glucosidase enzymes (EC 3.2.1.21) from Sclerotium rolfsii were studied and their contribution to cellulolysis is discussed.The enzymes are specific for substrates having the β-D-configuration.The specificity of the enzymes is not restricted to the β-D-(14) linkage, as all four β-D-glucosidases hydrolized substrates having β-D-(16)-,-(13) and -(12) linkages.The enzymes require strictly a D-gluco configuration for activity.The β-D-glucosidases had no action on highly ordered cellulose, such as Avicel, but slowly hydrolized disordered cellulose (phosphoric acid-swollen Avicel) and carboxymethylcellulose, and rapidly cellodextrins, removing D-glucose residues from the nonreducing end.The pure enzymes behaved rather as exo-β-D-glucan glucohydrolase.The Km values of all four β-D-glucosidases decreased with increase in the chain length of cellodextrins.Cellopentaose was the preferred substrate for all four enzymes.The major route of D-glucose formation from cellulose by hydrolysis with S.rolfsii β-D-glucosidases proceeds through higher-molecular weight cellodextrins.

Catalysis and inhibition of ester hydrolysis in the presence of resorcinarene hosts functionalized with dimethylamino groups

Cevasco, Giorgio,Thea, Sergio,Vigo, Daniele,Williams, Andrew,Zaman, Flora

, p. 630 - 636 (2006)

Complexation and catalysis of two calixresorcinarene (RES) derivatives with nucleophilic N,N-dimethylamino functions attached to their upper rims in the hydrolysis of carboxylate and sulfonate esters of 4-nitrophenol and 2,4-dinitrophenol have been investigated. Rate constants obey the complexation equation: kobs = kb × Ks + k c[Host]/Ks + [Host] Values of the dissociation constant (Ks) of the complexes are within the range exhibited by other systems such as cyclodextrins-ester complexes. The reactions of sulfonate esters only exhibit inhibition by the macrocyclic hosts. The reactions of the carboxylate esters exhibit catalysis and inhibition depending on the pH of the system. It is proposed that the dimethylamino function in RES3 and RES5 behaves as a nucleophile to form a reactive acylammonium species which subsequently decomposes and regenerates the catalytic amine. In the reaction of substituted phenyl acetates with RES3 the effective charge on the leaving oxygen in the complexed state (+0.88) is slightly more positive than that in the free ester (+0.70). The effective charge on the leaving oxygen in the transition structure is substantially more positive (+0.04 units) than in a model intramolecular reaction of tertiary dimethylamines with aryl esters (-0.53 units). The influence of the host on the reaction in the complex includes an electronic component which is ascribed to solvation of the transition structure of the rate-limiting step by water molecules located within the cavity of the host. It is suggested that this solvation is stronger than that occurring in the transition state for the model intramolecular reaction. Copyright

Solution or solid-it doesn't matter: Visible light-induced CO release reactivity of zinc flavonolato complexes

Anderson, Stacey N.,Larson, Michael T.,Berreau, Lisa M.

, p. 14570 - 14580 (2016)

Two types of zinc flavonolato complexes ([(6-Ph2TPA)Zn(flavonolato)]ClO4 and Zn(flavonolato)2) of four extended flavonols have been prepared, characterized, and evaluated for visible light-induced CO release reactivity. Zi

Clay entrapped Cu(OH)x as an efficient heterogeneous catalyst for ipso-hydroxylation of arylboronic acids

Dar, Bashir Ahmad,Bhatti, Prince,Singh,Lazar, Anish,Sharma, Parduman R.,Sharma, Meena,Singh, Baldev

, p. 60 - 67 (2013)

A remarkably active, selective and stable montmorilonite-KSF entrapped Cu(OH)x catalyst, has been prepared for the ipso-hydroxylation of arylboronic acids under ambient conditions without requirement of any ligand or base. This catalyst shows excellent reusability without leaching and any significant loss in catalytic activity. The catalyst was characterized using, XRD, SEM, TPR, IR, XPS and BET surface area measurement techniques.

A semisynthetic metalloenzyme based on a protein cavity that catalyzes the enantioselective hydrolysis of ester and amide substrates

Davies, Ronald R.,Distefano, Mark D.

, p. 11643 - 11652 (1997)

In an effort to prepare selective and efficient catalysts for ester and amide hydrolysis, we are designing systems that position a coordinated metal ion within a defined protein cavity. Here, the preparation of a protein-1,10-phenanthroline conjugate and the hydrolytic chemistry catalyzed by this construct are described. Iodoacetamido-1,10-phenanthroline was used to modify a unique cysteine residue in ALBP (adipocyte lipid binding protein) to produce the conjugate ALBP-Phen. The resulting material was characterized by electrospray mass spectrometry, UV/vis and fluorescence spectroscopy, gel filtration chromatography, and thiol titration. The stability of ALBP-Phen was evaluated by guanidine hydrochloride denaturation experiments, and the ability of the conjugate to bind Cu(II) was demonstrated by fluorescence spectroscopy. ALBP-Phen-Cu(II) catalyzes the enantioselective hydrolysis of several unactivated amino acid esters under mild conditions (pH 6.1, 25°C) at rates 32-280-fold above the background rate in buffered aqueous solution. In 24 h incubations 0.70 to 7.6 turnovers were observed with enantiomeric excesses ranging from 31% ee to 86% ee. ALBP-Phen-Cu(II) also promotes the hydrolysis of an aryl amide substrate under more vigorous conditions (pH 6.1, 37°C) at a rate 1.6 x 104-fold above the background rate. The kinetics of this amide hydrolysis reaction fit the Michaelis-Menten relationship characteristic of enzymatic processes. The rate enhancements for ester and amide hydrolysis reported here are 102-103 lower than those observed for free Cu(II) but comparable to those previously reported for Cu(II) complexes.

Synthesis of UDP-activated oligosaccharides with commercial β-galactosidase from Bacillus circulans under microwave irradiation

Kamerke, Claudia,Pattky, Martin,Huhn, Carolin,Elling, Lothar

, p. 27 - 34 (2012)

We report here on the synthesis of nucleotide activated oligosaccharides by transglycosylation with β-galactosidase from Bacillus circulans applying microwave irradiation (MWI) and conventional heating. The presented products could serve as novel inhibito

Synthesis of a Zr-Based Metal-Organic Framework with Spirobifluorenetetrabenzoic Acid for the Effective Removal of Nerve Agent Simulants

Park, Hea Jung,Jang, Jin Kyu,Kim, Seo-Yul,Ha, Jong-Woon,Moon, Dohyun,Kang, In-Nam,Bae, Youn-Sang,Kim, Suhkmann,Hwang, Do-Hoon

, p. 12098 - 12101 (2017)

A new microporous Zr(IV)-based metal-organic framework (MOF) containing 4,4′,4″,4t″-(9,9′-spirobi[fluorene]-2,2′,7,7′-tetrayl)tetrabenzoic acid (Spirof-MOF) was synthesized, characterized, and size-controlled for the adsorption and decomposition of a nerve agent simulant, dimethyl 4-nitrophenylphosphate (DMNP). Spirof-MOF showed a hydrolysis half-life (t1/2) of 7.5 min to DMNP, which was confirmed by using in situ 31P NMR spectroscopy. Additionally, size-controlled Spirof-MOFb (~1 μm) exhibited a half-life of 1.8 min and 99% removal within 18 min for DMNP. The results show that Spirof-MOF is a new active material in removing nerve agent simulants by adsorption and hydrolytic decomposition.

Decreased stability in liposomal suspensions: Accelerated loss of p-nitrophenyl acetate

Pejaver,Notari

, p. 1167 - 1171 (1985)

The goal of this investigation was to determine the reason for the previously reported increase in the rate of hydrolysis of p-nitrophenyl acetate to p-nitrophenol in the presence of positively charged liposomes. When this charge was due to incorporation

Purification and characterization of a mesophilic organic solvent tolerant lipase produced by Acinetobacter sp. K5b4

Al-Limoun, Muhamad O.,Khleifat, Khaled M.,Alsharafa, Khalid Y.,Qaralleh, Haitham N.,Alrawashdeh, Suddam A.

, p. 139 - 151 (2019)

The extracellular lipase produced by Acinetobacter sp. K5b4 was purified to homogeneity using ultrafiltration (cutoff 30 KDa) followed by gel filtration chromatography on Sephadex G-50. The enzyme was purified to homogeneity with an apparent molecular mas

Microheterogeneous solvation for aminolysis reactions in AOT-based water-in-oil microemulsions

Garcia-Rio, Luis,Mejuto, Juan Carlos,Perez-Lorenzo, Moises

, p. 4361 - 4373 (2005)

A kinetic study was carried out on the aminolysis of p-nitrophenyl acetate (NPA) by n-decylamine (DEC), piperazine (PIP) and sarcosine (SAR) in AOT/isooctane/water (w/o) microemulsions. By using the pseudophase model both the rate constants at the interfa

Bis (tributyltin) oxide. A mild, neutral and selective reagent for cleavage of esters. Scope and limitation of the reaction

Salomon, Claudio J.,Mata, Ernesto G.,Mascaretti, Oreste A.

, p. 4239 - 4242 (1991)

Bis(tributyltin)oxide acts as a mild, neutral and chemoselective ester cleavage reagent for a variety of carboxylic esters with good to excellent yields. The acyl-oxygen cleavage mechanism of (-)-(1R) menthyl acetate is discussed.

A simple, fast and excellent protocol for the synthesis of phenols using CuFe 2O 4 magnetic nanoparticles

Chutia, Rituparna,Chetia, Bolin

, (2019)

Abstract: This paper describes a very mild, quick and simple protocol for the synthesis of phenols using CuFe 2O 4 magnetic nanoparticles as a catalyst. The nanosized catalyst has an average diameter of 17.63 nm. The magnetic nanoparticles were characterized by SEM, EDX, VSM, XRD and TEM analysis. The synthesis of phenols from phenylboronic acids using H 2O 2 as an oxidant proceeded very well with excellent yields. Heterogeneous catalyst, easy recyclability, mild reaction conditions, short reaction time added as an advantage for the present protocol. Graphical Abstract: A very mild, quick and efficient protocol has been designed for the preparation of phenols from phenyl boronic acids using CuFe 2O 4 Magnetic Nanoparticles (MNPs) as a catalyst. Heterogeneous catalyst, easy recyclability added as an advantage for the protocol.[Figure not available: see fulltext.].

Controlled autocatalytic nitration of phenol in a microreactor

Ducry, Laurent,Roberge, Dominique M.

, p. 7972 - 7975 (2005)

(Chemical Equation Presented) Scaled-down approach: The nitration of phenol is an autocatalytic, strongly exothermic reaction and is thus difficult to handle on an industrial scale. Continuous nitration in a microreactor (see picture) affords higher yield

Hydrolysis of phosphoric acid ester across an enzyme membrane: Potato acid phosphatase immobilized on a Na-perfluorocarboxylate ionomer membrane for recovery of reaction product

Nomura, Kazuo,Liu, Mo

, p. 343 - 347 (2006)

Acid phosphatase from potato was immobilized onto the surface of the external solution side of a perfluorocarboxylate ionomer membrane using a cross-linking reagent. Based on the distinct difference in membrane permeabilities to 4-nitrophenol and 4-nitrop

Kinetics and mechanism of the reactions of polyallylamine with aryl acetates and aryl methyl carbonates

Castro, Enrique A.,Echevarria, Gerardo R.,Opazo, Alejandra,Robert, Paz S.,Santos, Jose G.

, p. 129 - 135 (2006)

The reactions of polyallylamine (PAA) with 4-nitrophenyl acetate (NPA), 2,4-dinitrophenyl acetate (DNPA), 2,4,6-trinitrophenyl acetate (TNPA), 4-nitrophenyl methyl carbonate (NPC), 2,4-dinitrophenyl methyl carbonate (DNPC) and 2,4,6-trinitrophenyl methyl carbonate (TNPC) at pH 7.0-11.5 were subjected to a kinetic investigation in aqueous solution at 25.0°C and an ionic strength of 0.1 M (KC1). Potentiometric titration curves were obtained at different polymer concentrations under the same conditions as for the kinetic measurements. The degree of dissociation (a) and pKapp values for PAA at each pH were found from the titration curves. The shape of these curves shows a conformational change of the polymer at α > 0.7. Similar behavior was observed through the dependence of logkN on either pH or a, where kN is the second-order rate constant for the title reactions. The KN value is influenced by the electrostatic interactions in the polymer chain and the conformational changes that PAA undergoes in solution. The Bronsted-type plots (logkN vs pkapp) are linear with slopes (β values) of 0.5, 0.4, 0.5, 0.7, 0.6 and 0.7 for the reactions of PAA with NPA, DNPA, TNPA, NPC, DNPC and TNPC, respectively. These data are consistent with concerted mechanisms. The k N values increase in the sequence TNPA > DNPA > NPA and TNPC > DNPC > NPC. These results are in accordance with those found for the reactions with monomeric amines, which are due to the increasing nucleofugality of the leaving groups, and also the increasing electrophilic character of the carbonyl carbon, as more nitro groups are added to the substrate. Acetates are more reactive than the corresponding methyl carbonates, which can be explained by the larger electron-releasing effect exerted by MeO relative to Me. PAA destabilizes the putative tetrahedral intermediate relative to the monomeric amines and the stability of tetrahedral intermediates would decrease in the sequence pyridines > anilines > secondary alicyclic amines > quinuclidines > PAA. Copyright

Hydrolysis of 4-Nitrophenyl Phosphate by (Amino Acidato)zinc Complexes

Viladkar, Sushama,Kamaluddin,Nath, Mala

, p. 2922 - 2926 (1993)

Simple zinc complexes of glycine, histidine, and cysteine are proposed as evolutionary models for hydrolytic enzymes.Catalytic activity of (amino acidato)zinc complexes has been studied towards hydrolysis of 4-nitrophenyl phosphate at 40 deg C over the pH

Molecular Characterization and Potential Synthetic Applications of GH1 β-Glucosidase from Higher Termite Microcerotermes annandalei

Arthornthurasuk, Siriphan,Jenkhetkan, Wantha,Suwan, Eukote,Chokchaichamnankit, Daranee,Srisomsap, Chantragan,Wattana-Amorn, Pakorn,Svasti, Jisnuson,Kongsaeree, Prachumporn T.

, p. 877 - 894 (2018)

A novel β-glucosidase from higher termite Microcerotermes annandalei (MaBG) was obtained via a screening method targeting β-glucosidases with increased activities in the presence of glucose. The purified natural MaBG showed a subunit molecular weight of 55?kDa and existed in a native form as a dimer without any glycosylation. Gene-specific primers designed from its partial amino acid sequences were used to amplify the corresponding 1,419-bp coding sequence of MaBG which encodes a 472-amino acid glycoside hydrolase family 1 (GH1) β-glucosidase. When expressed in Komagataella pastoris, the recombinant MaBG appeared as a ~ 55-kDa protein without glycosylation modifications. Kinetic parameters as well as the lack of secretion signal suggested that MaBG is an intracellular enzyme and not involved in cellulolysis. The hydrolytic activities of MaBG were enhanced in the presence of up to 3.5-4.5 M glucose, partly due to its strong transglucosylation activity, which suggests its applicability in biosynthetic processes. The potential synthetic activities of the recombinant MaBG were demonstrated in the synthesis of para-nitrophenyl-β-D-gentiobioside via transglucosylation and octyl glucoside via reverse hydrolysis. The information obtained from this study has broadened our insight into the functional characteristics of this variant of?termite GH1 β-glucosidase and its applications in bioconversion and biotechnology.

Structural and biochemical characterization of a metagenome-derived esterase with a long N-terminal extension

Okano, Hiroyuki,Hong, Xun,Kanaya, Eiko,Angkawidjaja, Clement,Kanaya, Shigenori

, p. 93 - 104 (2015)

The genes encoding six novel esterolytic/lipolytic enzymes, termed LC-Est1~6, were isolated from a fosmid library of a leaf-branch compost metagenome by functional screening using tributyrin agar plates. These enzymes greatly vary in size and amino acid s

Ultra-Fast Degradation of Chemical Warfare Agents Using MOF–Nanofiber Kebabs

Zhao, Junjie,Lee, Dennis T.,Yaga, Robert W.,Hall, Morgan G.,Barton, Heather F.,Woodward, Ian R.,Oldham, Christopher J.,Walls, Howard J.,Peterson, Gregory W.,Parsons, Gregory N.

, (2016)

The threat associated with chemical warfare agents (CWAs) motivates the development of new materials to provide enhanced protection with a reduced burden. Metal–organic frame-works (MOFs) have recently been shown as highly effective catalysts for detoxify

Hydrolysis of the RNA model substrate catalyzed by a binuclear ZrIV-substituted Keggin polyoxometalate

Luong, Thi Kim Nga,Absillis, Gregory,Shestakova, Pavletta,Parac-Vogt, Tatjana N.

, p. 15690 - 15696 (2015)

The reactivity and solution behaviour of the binuclear ZrIV-substituted Keggin polyoxometalate (Et2NH2)8[{α-PW11O39Zr(μ-OH)(H2O)}2]·7H2O (ZrK 2 : 2) towards

Synergistic Effect between La(III) and Hydrogen Peroxide in Phosphate Diester Cleavage

Takasaki, Bryan K.,Chin, Jik

, p. 9337 - 9338 (1993)

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Nitration of phenol over silica supported H4PW 11VO40 catalyst

Kumar, A. Sri Hari,Rao, K.T. Venkateswara,Upendar,Sailu, Ch.,Lingaiah,Prasad, P.S. Sai

, p. 37 - 40 (2012)

Vanadium incorporated tungstophosphoric acid (TPAV1) supported on silica was synthesized and characterized by BET-surface area, Fourier transform infrared spectroscopy, X-ray diffraction and Laser Raman techniques. Nitration of phenol was studied at room temperature (25 °C) using HNO 3 in the presence of 0-20 wt.% TPAV1/SiO2 catalysts taking 1, 2-dichloroethane as solvent. The effects of various parameters such as phenol/HNO3 mole ratio, reaction time, catalyst weight, and stirring speed on the catalyst activity were studied. 8 wt.% TPAV1/SiO2 has shown the best activity, regioselectivity and reusability in the nitration of phenol, with a conversion of 92.6% and o-nitrophenol selectivity of 97.9%.

Characterization of a thermostable esterase activity from the moderate thermophile Bacillus licheniformis.

Alvarez-Macarie,Augier-Magro,Baratti

, p. 1865 - 1870 (1999)

A new esterase activity from Bacillus licheniformis was characterized from an Escherichia coli recombinant strain. The protein was a single polypeptide chain with a molecular mass of 81 kDa. The optimum pH for esterase activity was 8-8.5 and it was stable

Mono- And Di-Sc-Substituted Keggin Polyoxometalates: Effective Lewis Acid Catalysts for Nerve Agent Simulant Hydrolysis and Mechanistic Insights

Chi, Yingnan,Dong, Jing,Hu, Changwen,Lin, Zhengguo,Zhang, Di,Zhang, Wenqi,Zhen, Ni

, (2020)

Recently, the hydrolysis of nerve agents by Lewis acid catalysts has attracted considerable attention. The development of molecular catalysts, such as polyoxometalates (POMs) with Lewis acidic sites, is helpful to improve degradation efficiency and understand the catalytic mechanism at a molecular level. Herein, two novel Keggin-type POMs, namely, mono-Sc-substituted K4[Sc(H2O)PW11O39]·22H2O·2(CH3COOK) (1) and di-Sc-substituted Na7[Sc2(CH3COO)2PW10O38]·10H2O·2CH3COONa (2), have been successfully synthesized and thoroughly characterized by routine techniques. To our knowledge, 1 and 2 represent the first example of discrete Sc-substituted Keggin clusters. Compared with the reported Sc-containing POMs, 1 and 2 exhibit relatively good solubility and stability in aqueous solution, as evidenced by 31P nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. The two Sc-substituted POMs can effectively catalyze the hydrolytic decontamination of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant, at near-neutral pH. Notably, the catalytic performance of 2 (conversion: 97percent) is much better than that of 1 (conversion: 28percent). It is found that the different coordination environment of Sc is the key factor to impact their activity. Mechanistic studies including the control experiments and spectroscopy analysis (13C nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry) show that under the turnover conditions the coordinated acetate dissociates from 2 and the exposed coordinatively unsaturated Sc center is more active than the water-coordinated Sc in 1 for binding with DMNP.

An unusual thioesterase promotes isochromanone ring formation in ajudazol biosynthesis

Buntin, Kathrin,Weissman, Kira J.,Mueller, Rolf

, p. 1137 - 1146 (2010)

The ajudazols are antifungal secondary metabolites produced by a hybrid polyketide synthase (PKS)-nonribosomal peptide synthetase (NRPS) multienzyme "assembly line" in the myxobacterium Chondromyces crocatus Cm c5. The most striking structural feature of

Fabrication of dual catalytic microcapsules by mesoporous graphitic carbon nitride (mpg-C3N4) nanoparticle-enzyme conjugate stabilized emulsions

Varshney, Rohit,Kumar, Sushil,Ghosh, Kaushik,Patra, Debabrata

, p. 3097 - 3102 (2020)

Emulsionlated microcapsules (MCs) were fabricated by simultaneous self-assembly and crosslinking of mpg-C3N4 nanoparticles (NPs) and lipase conjugates at an oil-water interface. The presence of both enzymes and mpg-C3Nsub

Highly efficient nitration of phenolic compounds in solid phase or solution using Bi(NO3)3·5H2O as nitrating reagent

Sun, Hong-Bin,Hua, Ruimao,Yin, Yingwu

, p. 9071 - 9073 (2005)

Bi(NO3)3·5H2O was used as an efficient nitrating reagent in the nitration of phenolic compounds to give nitrated phenols in good to high yields. The nitration reaction proceeded smoothly by grinding 1 equiv of phenol, 2-methylphenol, 4-methylphenol, or 4-chlorophenol and Bi(NO3)3· 5H2O, and the nitration of other phenolic compounds could be performed in acetone at ambient temperature (22-30 °C).

A mild and chemoselective method for deprotection of aryl acetates and benzoates under non-hydrolytic condition

Chakraborti, Asit K,Sharma, Lalima,Sharma, Upasana

, p. 9343 - 9346 (2001)

Chemoselective deprotection of aryl acetates and benzoates can be achieved under non-hydrolytic condition by treatment with K2CO3 in N-methyl-2-pyrrolidone (NMP) at 100°C. Selective cleavage of aryl acetates and benzoates take place in the presence of alkyl carboxylates during intramolecular competitions.

Kartaschew

, (1928)

Enantioselective Ester Hydrolysis Catalyzed by Imprinted Polymers

Sellergren, Boerje,Shea, Kenneth J.

, p. 1403 - 1406 (1994)

The first imprinted polymers with enantioselective catalytic activity are reported.

Benzoxazole-Linked Ultrastable Covalent Organic Frameworks for Photocatalysis

Wei, Pi-Feng,Qi, Ming-Zhu,Wang, Zhi-Peng,Ding, San-Yuan,Yu, Wei,Liu, Qiang,Wang, Li-Ke,Wang, Huai-Zhen,An, Wan-Kai,Wang, Wei

, p. 4623 - 4631 (2018)

The structural uniqueness of covalent organic frameworks (COFs) has brought these new materials great potential for advanced applications. One of the key aspects yet to be developed is how to improve the robustness of covalently linked reticular frameworks. In order to make the best use of π-conjugated structures, we develop herein a ";killing two birds with one stone" strategy and construct a series of ultrastable benzoxazole-based COFs (denoted as LZU-190, LZU-191, and LZU-192) as metal-free photocatalysts. Benefiting from the formation of benzoxazole rings through reversible/irreversible cascade reactions, the synthesized COFs exhibit permanent stability in the presence of strong acid (9 M HCl), strong base (9 M NaOH), and sunlight. Meanwhile, reticulation of the benzoxazole moiety into the π-conjugated COF frameworks decreases the optical band gap and therefore increases the capability for visible-light absorption. As a result, the excellent photoactivity and unprecedented recyclability of LZU-190 (for at least 20 catalytic runs, each with a product yield of 99%) have been illustrated in the visible-light-driven oxidative hydroxylation of arylboronic acids to phenols. This contribution represents the first report on the photocatalytic application of benzoxazole-based structures, which not only sheds new light on the exploration of robust organophotocatalysts from small molecules to extended frameworks but also offers in-depth understanding of the structure-activity relationship toward practical applications of COF materials.

Reduction processes biocatalyzed by Vigna unguiculata

Bizerra, Ayla M.C.,Gonzalo, Gonzalo de,Lavandera, Ivan,Gotor-Fernandez, Vicente,de Mattos, Marcos Carlos,de Oliveira, Maria da Conceicao F.,Lemos, Telma L.G.,Gotor, Vicente

, p. 566 - 570 (2010)

Whole cells from the Brazilian beans feijao de corda (Vigna unguiculata) have been employed as biocatalysts in different bioreduction processes. Good to excellent selectivities can be obtained in the reduction of aromatic and aliphatic ketones, as well as β-ketoesters, depending on the conversions and the chemoselectivity on the substrate structure. This biocatalyst was also able to reduce the nitro moiety of different aromatic nitro compounds, showing as well enoate reductase activity, and chemoselectively catalyzing the double bond reduction of 4-phenyl-3-buten-2-one with moderate conversion.

-

Shiffman,R. et al.

, p. 3279 - 3284 (1977)

-

Role of peroxophosphate intermediates in reactions of tris(4-nitrophenyl) phosphate and phenyl phosphorochloridate with alkaline hydrogen peroxide

Foroudian, Houshang J.,Gillitt, Nicholas D.,Bunton, Clifford A.,Yatsimirsky, Anatoly K.

, p. 310 - 314 (2001)

Reaction of alkaline hydrogen peroxide with tris(4-nitrophenyl) phosphate generates ca 1.5 equiv. of 4-nitrophenol per mole of substrate with no evidence of build-up of an intermediate, and reaction of bis(4-nitrophenyl) phosphate anion is too slow to give a product. The initially formed bis(4-nitrophenyl) peroxophosphate is assumed to decompose to the phosphate ester by reaction with H2O2 or to eliminate 4-nitrophenoxide ion with the formation of a transient cyclic peroxophosphate. Reaction of phenyl phosphorochloridate anion with HO2- does not give phenoxide ion by this intramolecular reaction. Semi-empirical and ab initio simulations indicate that elimination of aryloxide ion from an aryl peroxophosphate should generate a cyclic rather than an open-chain peroxophosphate. Copyright

Aryl sulfamates are broad spectrum inactivators of sulfatases: Effects on sulfatases from various sources

Bojarova, Pavla,Williams, Spencer J.

, p. 477 - 480 (2009)

Aryl sulfamates were originally developed as inhibitors of steroid sulfatase, and have recently been shown to be powerful inactivators of a bacterial sulfatase, PaAtsA from Pseudomonas aeruginosa. We demonstrate that a simple aryl sulfamate, 3-nitrophenyl

Multiscale immobilized lipase for rapid separation and continuous catalysis

Ren, Weifan,Fei, Xu,Tian, Jing,Li, Yao,Jing, Muzi,Fang, Huan,Xu, Longquan,Wang, Yi

, p. 13471 - 13478 (2018)

Enzyme-inorganic hybrid nanoflowers have drawn extensive research interest for enzyme immobilization owing to their enhanced enzymatic activity, high surface area, and excellent chemical stability. However, their low mechanical stability and challenging s

Extracellular α-galactosidase from Debaryomyces hansenii UFV-1 and its use in the hydrolysis of raffinose oligosaccharides

Viana, Pollyanna A.,De Rezende, Sebastiao T.,Marques, Virginia M.,Trevizano, Larissa M.,Passos, Flavia M. L.,Oliveira, Maria G. A.,Bemquerer, Marcelo P.,Oliveira, Jamil S.,Guimaraes, Valeria M.

, p. 2385 - 2391 (2006)

Raffinose oligosaccharides (RO) are the factors primarily responsible for flatulence upon ingestion of soybean-derived products. ROs are hydrolyzed by α-galactosidases that cleave α-1,6-linkages of α-galactoside residues. The objectives of this study were

Reactivity of p-substituted benzaldoximes in the cleavage of p-nitrophenyl acetate: Kinetics and mechanism

Picha, Jan,Cibulka, Radek,Hampl, Frantisek,Liska, Frantisek,Parik, Patrik,Pytela, Oldrich

, p. 397 - 413 (2004)

Eleven p-substituted benzaldoximes (p-XC6H4CH=NOH, where X = H, CH3, CF3, F, Cl, Br, OCH3, N(CH3)2, COOCH3, CN, NO2) have been synthesized and their dissociation constants determined in 10% (v/v) aqueous dioxane at 35°C. Under the same conditions, the pseudofirst order rate constants kobs of their reactions with p-nitrophenyl acetate (PNPA) were measured at pH values from 7.8 to 10.8 and at concentrations c oxime ranging from 0 to 4:00 x 10-3 mol l-1. The kinetic model and mechanism of the said reaction was proposed by means of mathematical statistical modelling of the dependences of kobs on pH and coxime. The mechanism involves a pre-equilibrium (k -1/k1) in which PNPA forms a tetrahedral intermediate (THI) with the deprotonated form of oxime. In the given medium, THI is in equilibrium with the non-reactive conjugated acid THIH (dissociation constant Ka,THIH) which is stabilized by intramolecular hydrogen bond. Depending on pH, the rate-limiting step consists either in formation of THI from educts (pH a,oxime) or in its spontaneous (k 2) and oxime-catalyzed (k3, general acid catalysis) decomposition to products (pH > pKa/oxime). Evaluation of substituent effects on dissociation constants (Ka,oxime) of the oximes showed that there is no direct conjugation between the substituent and the reaction centre (the found reaction constant ρ(Ka,oxime) = 0.91). The transmission coefficient of the transfer of these effects through C=N-O grouping corresponds approximately to one bond. The reaction constants in the Hammett equation obtained from the regression model are: ρ(k -1Ka,THIH/k1) = 1.29, ρ(k2K a,THIH) = 0.20 and ρ(k3Ka,THIH) = 0.67. These reaction constants have been discussed with the regard to the reaction mechanism suggested.

A MICELLAR MODEL OF ZINC CONTAINING METALLOENZYMES

Eiki, Toshio,Mori, Mikio,Kawada, Shuji,Matsushima, Kazumi,Tagaki, Waichiro

, p. 1431 - 1434 (1980)

N-Dodecyl-2-hydroxymethylimidazole (1) was found to be unusually active in the transesterification toward p-nitrophenyl picolinate (4), when the reaction wasd carried out in the presence of CTABr micelle and zinc ion.

Syntheses, crystal structures, and properties of Cu(II) and Zn(II) complexes with an asymmetric tripodal ligand

Sun, Wenwu,Cheng, Qingrong,Zhou, Hong,Pan, Zhiquan

, p. 56 - 65 (2013)

[Cu2L2](ClO4)2 (1) and [Zn 2L2](ClO4)2 (2) (HL = 2-[bis(3-aminopropyl)amino]propanol) have been synthesized and characterized. X-ray crystallography analyses show that

Cloning, sequencing, and expression of the gene encoding the Clostridium stercorarium alpha-galactosidase Aga36A in Escherichia coli.

Suryani,Kimura, Tetsuya,Sakka, Kazuo,Ohmiya, Kunio

, p. 2160 - 2166 (2003)

The alpha-galactosidase gene aga36A of Clostridium stercorarium F-9 was cloned, sequenced, and expressed in Escherichia coli. The aga36A gene consists of 2,208 nucleotides encoding a protein of 736 amino acids with a predicted molecular weight of 84,786.

Dramatic Ligand Effect in Copper(II) Complex Promoted Transesterification of a Phosphate Diester

Wahnon, Daphne,Hynes, Rosemary C.,Chin, Jik

, p. 1441 - 1442 (1994)

A cis-diaqua copper(II) complex has been shown to promote the transesterification of a phosphate diester with second-order dependence on the metal complex.

On the effect of 2-propanol on phenol photonitration upon nitrate photolysis

Vione, Davide,Sur, Babita,Dutta, Binay K.,Maurino, Valter,Minero, Claudio

, p. 68 - 70 (2011)

It is shown that the enhancement by 2-propanol of the nitration of phenol upon nitrate photolysis is compatible with the inhibition by the alcohol of in-cage recombination between O- and NO2. This effect would increase the availabili

Facile surface functionalization of hydrophobic magnetic nanoparticles

Liu, Yuan,Chen, Tao,Wu, Cuichen,Qiu, Liping,Hu, Rong,Li, Juan,Cansiz, Sena,Zhang, Liqin,Cui, Cheng,Zhu, Guizhi,You, Mingxu,Zhang, Tao,Tan, Weihong

, p. 12552 - 12555 (2014)

Nonpolar phase synthesized hydrophobic nanocrystals show attractive properties and have demonstrated prominent potential in biomedical applications. However, the preparation of biocompatible nanocrystals is made difficult by the presence of hydrophobic surfactant stabilizer on their surfaces. To address this limitation, we have developed a facile, high efficiency, single-phase and low-cost method to convert hydrophobic magnetic nanoparticles (MNPs) to an aqueous phase using tetrahydrofuran, NaOH and 3,4-dihydroxyhydrocinnamic acid without any complicated organic synthesis. The as-transferred hydrophilic MNPs are water-soluble over a wide pH range (pH = 3-12), and the solubility is pH-controllable. Furthermore, the as-transferred MNPs with carboxylate can be readily adapted with further surface functionalization, varying from small molecule dyes to oligonucleotides and enzymes. Finally, the strategy developed here can easily be extended to other types of hydrophobic nanoparticles to facilitate biomedical applications of nanomaterials.

Porous conjugated polymer via metal-free synthesis for visible light-promoted oxidative hydroxylation of arylboronic acids

Wang, Zi Jun,Li, Run,Landfester, Katharina,Zhang, Kai A.I.

, p. 291 - 295 (2017)

Porous conjugated polymers have emerged recently as efficient metal-free and visible light-active photocatalysts. However, the synthesis of this new class of materials usually requires transition metal catalysts such as palladium. A metal-free synthetic route still remains a huge challenge for the chemists. Here we report on a metal-free pathway of a porous conjugated polymer via simple Knoevenagel polycondensation under mild reaction conditions. The obtained polymer exhibited a high surface area and could be applied as a robust and efficient heterogeneous photocatalyst for the oxidative hydroxylation of arylboronic acids under visible light irradiation with a high functional group tolerance of the substrates.

Carbohydrate esterases of family 2 are 6-O-deacetylases

Topakas, Evangelos,Kyriakopoulos, Sarantos,Biely, Peter,Hirsch, Jan,Vafiadi, Christina,Christakopoulos, Paul

, p. 543 - 548 (2010)

Three acetyl esterases (AcEs) from the saprophytic bacteria Cellvibrio japonicus and Clostridium thermocellum, members of the carbohydrate esterase (CE) family 2, were tested for their activity against a series of model substrates including partially acet

New structural motif for carboxylic acid perhydrolases

Yin, Delu,Purpero, Vince M.,Fujii, Ryota,Jing, Qing,Kazlauskas, Romas J.

, p. 3037 - 3046 (2013)

Some serine hydrolases also catalyze a promiscuous reaction - reversible perhydrolysis of carboxylic acids to make peroxycarboxylic acids. Five X-ray crystal structures of these carboxylic acid perhydrolases show a proline in the oxyanion loop. Here, we test whether this proline is essential for high perhydrolysis activity using Pseudomonas fluorescens esterase (PFE). The L29P variant of this esterase catalyzes perhydrolysis 43-fold faster (kcat comparison) than the wild type. Surprisingly, saturation mutagenesis at the 29 position of PFE identified six other amino acid substitutions that increase perhydrolysis of acetic acid at least fourfold over the wild type. The best variant, L29I PFE, catalyzed perhydrolysis 83-times faster (kcat comparison) than wild-type PFE and twice as fast as L29P PFE. Despite the different amino acid in the oxyanion loop, L29I PFE shows a similar selectivity for hydrogen peroxide over water as L29P PFE (β0=170 vs. 160 M-1), and a similar fast formation of acetyl-enzyme (140 vs. 62 U mg-1). X-ray crystal structures of L29I PFE with and without bound acetate show an unusual mixture of two different oxyanion loop conformations. The type II β-turn conformation resembles the wild-type structure and is unlikely to increase perhydrolysis, but the type I β-turn conformation creates a binding site for a second acetate. Modeling suggests that a previously proposed mechanism for L29P PFE can be extended to include L29I PFE, so that an acetate accepts a hydrogen bond to promote faster formation of the acetyl-enzyme. Ulterior motif: An esterase variant (L29I; see figure) uses a new mechanism for perhydrolysis of acetic acid, likely involving a second acetate molecule. X-ray crystal structures of L29I PFE with and without bound acetate show an unusual mixture of two different oxyanion loop conformations that creates a binding site for the second acetate. Copyright

Rapid and green synthesis of phenols catalyzed by a deep eutectic mixture based on fluorinated alcohol in water

Wang, Liang,Dai, Dong-Yan,Chen, Qun,He, Ming-Yang

, p. 44 - 47 (2014)

A new deep eutectic mixture based on choline chloride and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was prepared and was found to be effective for the rapid transformation of aryl/heteroaryl boronic acids to the corresponding phenols in water using hydrogen peroxide as the oxidant. Broad substrate compatibility, metal- and additive-free conditions as well as reusability of the catalyst made this procedure more environmentally benign.

Room-Temperature Ionic Liquids (RTILs) as Green Media for Metal- and Base-Free ipso -Hydroxylation of Arylboronic Acids

Kim, Seung-Hoi,Kwon, Gyu-Tae,Shin, Eun-Jae

, p. 1815 - 1819 (2019)

The oxidative hydroxylation of arylboronic acids to the corresponding phenolic compounds under metal- and base-free aerobic conditions is successfully demonstrated on a greener media. Hydrogen peroxide, as an eco-friendly oxidant, is compatible with green mediates room-temperature ionic liquids (RTIL)s, providing hydroxylation products of arylboronic acids in an efficient manner. The RTIL support is particularly interesting for its reusability.

Reaction of Benzene Radical Cation with Water. Evidence for the Reversibility of OH Radical Addition to Benzene

Eberhardt, Manfred K.

, p. 3876 - 3878 (1981)

The thermal decomposition of Na2S2O8 at 80 deg C in aqueous solutions of benzene and nitrobenzene gives phenol, biphenyl, and o- and p-nitrophenol in high yield.In the absence of benzene or if benzene is replaced by toluene or anisole no nitrophenols are formed under otherwise identical conditions.This indicates a direct involvement of the benzene radical cation in the hydroxylation of nitrobenzene.The benzene radical cation reacts with water to give hydroxycyclohexadienyl radical, which in turn can dissociate to benzene and OH radicals.The effect of oxygen, Cu2+, pH, and benzene concentration on the product yields has been investigated.

β-Galactosidase from Ginkgo biloba seeds active against β-galactose-containing N-glycans: Purification and characterization

Rahman, M. Ziaur,Maeda, Megumi,Kimura, Yoshinobu

, p. 1464 - 1472 (2015)

In this study, we purified an acidic β-galactosidase to homogeneity from Ginkgo biloba seeds (β-Gal'ase Gb-1) with approximately 270-fold purification. A molecular mass of the purified β-Gal'ase Gb-1 was estimated about 35 kDa by gel filtration and 32 kDa

Lipase and Laccase Encapsulated on Zeolite Imidazolate Framework: Enzyme Activity and Stability from Voltammetric Measurements

Naseri, Maryam,Pitzalis, Federica,Carucci, Cristina,Medda, Luca,Fotouhi, Lida,Magner, Edmond,Salis, Andrea

, p. 5425 - 5433 (2018)

Abstract: Lipase (Pseudomonas fluorescens) and laccase (Trametates versicolor) were encapsulated on two zeolite imidazolate framework, ZIF-8 and ZIF-zni, materials using a one-pot synthesis-immobilization method in aqueous solution at room temperature. Th

New Zn(II) complexes based on biologically active substituted acetic acid and nitrogen donor ligands: synthesis, crystal structure and biological applications

Kamel, Shayma,Abu Ali, Hijazi,Abu Shamma, Amani

, p. 1910 - 1925 (2017)

The complexes [Zn(phenylacetato)2(2-aminopyridin)2] (3), [Zn(phenylacetato)2(1,10-phenanthroline)]·H2O (4), and [Zn(phenylacetato)2(2,9-dimethyl-1,10-phenanthroline)]·0.5 H2O (5) were prepa

Molecular Recognition and Catalysis. Acceleration of Phosphodiester Cleavage by a Simple Hydrogen-Bonding Receptor

Jubian, Vrej,Dixon, Robert P.,Hamilton, Andrew D.

, p. 1120 - 1121 (1992)

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The reaction of peroxynitrite with organic molecules bearing a biologically important functionality. The multiplicity of reaction modes as exemplified by hydroxylation, nitration, nitrosation, dealkylation, oxygenation, and oxidative dimerization and cleavage

Nonoyama, Nobuaki,Oshima, Hiroshi,Shoda, Chizuru,Suzuki, Hitomi

, p. 2385 - 2395 (2001)

The reactions of peroxynitrite with a variety of organic molecules which include a biologically important functionality have been examined to construct a simple model for the peroxynitrite-induced in vivo transformations as well as a chemical probe for the active species involved therein. Phenols were found to undergo hydroxylation, nitration, oxidative dimerization, and oxidation to cyclohexadienones and quinones. The ring nitration of catechol was confirmed for the first time in the in vitro reaction of peroxynitrite. Dealkylation and N-oxide formation were the major reaction modes observed for N,N-dimethyl-p-toluidine. 1,2-Phenylenediamine gave benzotriazole in high yield. The electron-deficient C-C double bond in 1,4-naphthoquinone underwent epoxidation, while the electron-rich C-C double bond in α-methylstyrene suffered oxidative cleavage to acetophenone. The activated double bond in trans-stilbene underwent oxidative cleavage and epoxidation in parallel to give benzaldehyde and trans-stilbene oxide as the major products. The triple bond in diphenylacetylene was simply oxygenated to form benzil, together with trace amounts of ring nitration products. 1-Phenylethanol, imidazole, 2′-deoxyadenosine, and 2′-deoxyguanosine were all quite slow to react, while uracil and cytosine were almost inert to peroxynitrite. The reaction modes exhibited by peroxynitrite are too widespread and complicated to explain the whole mechanistic pathway in terms of a single active species. All reaction modes observed for the peroxynitrite to date could be classified into five categories according to their types: i) electron transfer type, ii) O-electrophilic type, iii) N-electrophilic type, iv) O-nucleophilic type, and v) radical type. Some of these may compete under certain conditions. The active species involved in each of these types of reactions are as follows: i) NO+, NO2, and OH, ii) ONOOH, iii) ONOOH and NO+, iv) OOH- and ONOO-, and v) NO2 and OH.

Nucleobase-containing metallated polymeric resins as artificial phosphodiesterases: Kinetics of hydrolysis, pH dependence, and catalyst recycling

Srivatsan,Verma, Sandeep

, p. 828 - 833 (2001)

Two metallated polymeric resins that contain the nucleobase adenine have been investigated for their ability to catalyze the hydrolysis of model phosphodiester substrates. These resins behave in a catalytic manner and display classical Michaelis-Menten ki

Structural and mechanistic insights into a Bacteroides vulgatus retaining N-acetyl-β-galactosaminidase that uses neighbouring group participation

Roth,Petricevic,John,Goddard-Borger,Davies,Williams

, p. 11096 - 11099 (2016)

Bacteroides vulgatus is a member of the human microbiota whose abundance is increased in patients with Crohn's disease. We show that a B. vulgatus glycoside hydrolase from the carbohydrate active enzyme family GH123, BvGH123, is an N-acetyl-β-galactosamin

Catalysis of carbamate hydrolysis by vancomycin and semisynthetic derivatives

Shi,Griffin

, p. 6482 - 6486 (1993)

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The role of the medium in solvent isotope effects on serine protease action

Tian, Jiaher,Tan, Jue,Schowen, K. Barbara,Schowen, Richard L.

, p. 781 - 786 (1999)

The hydrolysis of N-carbobenzyloxyaminoacyl-O-p-nitrophenyl esters derived from L-leucine, L-phenylalanine, and L-tryptophan, with catalysis by bovine pancreatic α-chymotrypsin at pH 7.00 at 25.00°C in water containing acetonitrile from 15.0% to 60% (v/v)

Banana pulp extract mediated synthesis of Cu2O nanoparticles: An efficient heterogeneous catalyst for the ipso-hydroxylation of arylboronic acids

Borah, Rupom,Saikia, Eramoni,Bora, Sankar Jyoti,Chetia, Bolin

, p. 1211 - 1215 (2017)

A green and facile novel procedure has been developed for the synthesis of Cu2O nanoparticles within a very short reaction time using banana pulp extract as a reducing agent. The synthesized nanoparticles are well characterized by SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) and powder XRD (X-ray Diffraction) methods. An environmental benign and highly efficient protocol for the ipso-hydroxylation of aryl and hetero arylboronic acids using bio-fabricated Cu2O nanoparticles as a catalyst and aqueous H2O2as an oxidant has also been developed. The main advantages of this protocol are the base free reaction condition, reusable and heterogeneous catalytic system, and short reaction time with excellent yields.

Enzymatic characterization of O-GlcNAcase isoforms using a fluorogenic GlcNAc substrate

Kim, Eun Ju,Kang, Dae Ook,Love, Dona C.,Hanover, John A.

, p. 971 - 982 (2006)

A highly sensitive fluorogenic hexosaminidase substrate, fluorescein di(N-acetyl-β-d-glucosaminide) (FDGlcNAc), was prepared essentially as described previously [Chem. Pharm. Bull. 1993, 41, 314] with some modifications. The fluorescent analog is a substrate for a number of hexosaminidases but here we have focused on the cytoplasmic O-GlcNAcase isoforms. Kinetic analysis using purified O-GlcNAcase and its splice variant (v-O-GlcNAcase) expressed in Escherichia coli suggests that FDGlcNAc is a much more efficient substrate (Km = 84.9 μM) than the conventional substrate, para-nitrophenyl 2-acetamido-2-deoxy-β-d-glucopyranoside (pNP-β-GlcNAc, Km = 1.1 mM) and a previously developed fluorogenic substrate, 4-methylumbelliferyl 2-acetamido-2-deoxy-β-d-glucopyranoside [MUGlcNAc, Km = 0.43 mM; J. Biol. Chem. 2005, 280, 25313] for O-GlcNAcase. The variant O-GlcNAcase, a protein lacking the C-terminal third of the full-length O-GlcNAcase, exhibited a Km of 2.1 mM with respect to FDGlcNAc. This shorter isoform was not previously thought to exhibit O-GlcNAcase activity based on in vitro studies with pNP-β-GlcNAc. However, both O-GlcNAcase isoforms reduced O-GlcNAc protein levels extracted from HeLa and HT-29 cells in vitro, indicating that the splice variant is a bona fide O-GlcNAcase. Fluorescein di-N-acetyl-β-d-galactosaminide (FDGalNAc) is not cleaved by these enzymes, consistent with previous findings that the O-GlcNAcase has substrate specificity toward O-GlcNAc but not O-GalNAc. The enzymatic activity of the shorter isoform of O-GlcNAcase was first detected by using highly sensitive fluorogenic FDGlcNAc substrate. The finding that O-GlcNAcase exists as two distinct isoforms has a number of important implications for the role of O-GlcNAcase in hexosamine signaling.

Proton-Transfer Equilibria between Notrophenols and Alkylamines in N-Methylformamide

Oncescu, T.,Oancea, A.-M.,Maeyer, L. De

, p. 2593 - 2599 (1983)

The equilibrium constants, Ke, of the proton-transfer reactions between o-, m-, and p-nitrophenols (ONP, MNP, and PNP, respectively), and monomethylamine and di- and triethylamines (MNA, DEA, and TEA, respectively) in N-methylformamide (NMF) were measured spectrophotometrically by using amine-amine hydrochloride buffers at different temperatures and 0.1-0.2 M ionic strength.Together with the previously measured pKa of p-nitrophenol, these values allowed the determination of the acidity constants of alkylamines and the other nitrophenols in this solvent.The reported values are compared with literature data in other media including the gas phase.The reaction enthalpies and entropies are also reported and discussed for some of these systems.

Oxidative inactivation of protein tyrosine phosphatase 1B by organic hydroperoxides

Bhattacharya, Sanjib,LaButti, Jason N.,Seiner, Derrick R.,Gates, Kent S.

, p. 5856 - 5859 (2008)

Protein tyrosine phosphatases (PTPs) are cysteine-dependent enzymes that play a central role in cell signaling. Organic hydroperoxides cause thiol-reversible, oxidative inactivation of PTP1B in a manner that mirrors the endogenous signaling agent hydrogen

Single open sites on FeIIions stabilized by coupled metal ions in CN-deficient prussian blue analogues for high catalytic activity in the hydrolysis of organophosphates

Yamane, Mari,Tabe, Hiroyasu,Kawakami, Masami,Tanaka, Hisashi,Kawamoto, Tohru,Yamada, Yusuke

, p. 16000 - 16009 (2020)

CN-deficient Prussian blue analogues (PBAs), [MN(H2O)x]y[FeII(CN)5(NH3)] (MN = CuII, CoII, or GaIII), were synthesized and examined as a new class of heterogeneous catalysts for hydrolytic decomposition of organophosphates often used as pesticides. The ac

Kinetics and Mechanism of the Aminolysis of Phenyl and Methyl 4-Nitrophenyl Thionocarbonates

Castro, Enrique A.,Saavedra, Claudia,Santos, Jose G.,Umana, Maria I.

, p. 5401 - 5407 (1999)

The reactions of secondary alicyclic amines with the title substrates are subjected to a kinetic study in aqueous solution, 25.0°C, ionic strength 0.2 (KCl), by following spectrophotometrically the release of 4-nitrophenoxide ion. Under amine excess, pseu

Multiple Reaction Products from the Hydrolysis of Chiral and Prochiral Organophosphate Substrates by the Phosphotriesterase from Sphingobium sp. TCM1

Bigley, Andrew N.,Narindoshvili, Tamari,Xiang, Dao Feng,Raushel, Frank M.

, p. 1842 - 1846 (2018)

The phosphotriesterase from Sphingobium sp. TCM1 (Sb-PTE) is notable for its ability to hydrolyze organophosphates that are not substrates for other enzymes. In an attempt to determine the catalytic properties of Sb-PTE for hydrolysis of chiral phosphotriesters, we discovered that multiple phosphodiester products are formed from a single substrate. For example, Sb-PTE catalyzes the hydrolysis of the RP-enantiomer of methyl cyclohexyl p-nitrophenyl phosphate with exclusive formation of methyl cyclohexyl phosphate. However, the enzyme catalyzes hydrolysis of the SP-enantiomer of this substrate to an equal mixture of methyl cyclohexyl phosphate and cyclohexyl p-nitrophenyl phosphate products. The ability of this enzyme to catalyze the hydrolysis of a methyl ester at the same rate as the hydrolysis of a p-nitrophenyl ester contained within the same substrate is remarkable. The overall scope of the stereoselective properties of this enzyme is addressed with a library of chiral and prochiral substrates.

Efficient Multi-point Interaction between Peptide Catalysts and Amino Acid Esters in a Bilayer Vesicular Membrane for Highly Stereoselective Hydrolysis Reactions

Ohkubo, Katsutoshi,Urabe, Kenji,Yamamoto, Junji,Ishida, Hitoshi,Usui, Satoshi,Sagawa, Takashi

, p. 2301 - 2302 (1995)

The 1H NMR NOESY spectra of the multi-point interaction between N-(N-benzyloxycarbonyl-L-leucyl)-L-histidine- and methyl N-hexanoyl-L-phenylalanate in a N,N-bisdodecyl-N,N-dimethylammonium bromide membrane confirms that the membrane-assis

Kinetic and mechanistic studies of the hydrolysis of sulfamate esters: a non-elimination decomposition route

Spillane, William J.,McCaw, Cheryl J.A.,Maguire, Neil P.

, p. 1049 - 1052 (2008)

The kinetics of hydrolysis at pH 2 and ionic strength (μ) = 1 of a series of sulfamate esters p-XC6H4OSO2NH2 have been examined using structure- and solvent-reactivity studies, thermodynamic data, a 'nucleophilicity test' and a kinetic solvent isotope effect to probe the mechanism of the hydrolysis. These esters can be regarded as models for the more complex medicinally and biologically important esters now under extensive study. The mechanism of hydrolysis involves the neutral ester undergoing nucleophilic attack by water in a bimolecular TS.

Sodium dodecyl sulfate-polyethyleneimine-water system. Self-organization and catalytic activity

Zakharova,Valeeva,Kudryavtsev,Bilalov,Tret'yakova,Kudryavtseva,Konovalov,Barabanov

, p. 641 - 649 (2005)

Concentration boundaries within which polymer-colloid structures exist in a sodium dodecyl sulfate-polyethyleneimine-water system were determined. The catalytic effect of this composition was found for the hydrolysis of phosphonic acid esters. The found acceleration of hydrolysis up to 25-fold is caused by reagent concentrating in a catalytic complex.

Fingerprinting a Transition-Structure Guest by a Building-Block Approach with an Incremental Series of Catalytic Hosts. Structural Requirements for Glyme and α,ω-Dimethoxyalkane Catalyses in N-Methylbutylaminolysis and Butylaminolysis of 4-Nitrophenyl Acetate in Chlorobenzene

Hogan, John C.,Gandour, Richard D.

, p. 55 - 61 (1992)

Glymes, H-(CH2OCH2)n-H, GLM(n), catalyze butylaminolysis of 4-nitrophenyl acetate in chlorobenzene.Values of kcat/Oxy, where Oxy is the number of oxygens in the catalyst, increase with oligomer length up to triglyme, GLM(4), and then plateau.Optimal catalysis on a per oxygen basis requires a -(CH2OCH2)4-fragment, which suggests a four-point recognition of the secondary ammonium ion of the zwitterionic tetrahedral intermediate (TI) (J.Org.Chem. 1991, 56, 2821-2826).Dissection of individual structural components and reassembly to the same structure of the complexverifies this model.The following kinetic studies of 4-nitrophenyl acetate in chlorobenzene have accomplished the task: (a) methylbutylaminolysis catalyzed by GLM(n), n = 2-4; (b) methylbutylaminolysis catalyzed by α,ω-dimethoxyalkanes, CH3O-(CH2)n-OCH3, DME(n), n = 2-10 and 12; and (c) butylaminolysis catalyzed by DME(n), n = 2-10 and 12.Experiment a has revealed that kcat/Oxy is the same for GLM(2) - GLM(4).Optimal catalysis for breakdown of a zwitterionic TI with one ammonium proton only requires a -(CH2OCH2)2-fragment.Experiment b has shown that kcat/Oxy is largest for DME(2) with the values for the remaining DMEs 2 - 2.5-fold lower.A -CH2CH2- is the best spacer between the two oxygens.Thus, bifurcated hydrogen-bond formation between the two oxygens and the one ammonium proton enhances catalysis.Experiment c has revealed that kcat/Oxy for DME(2) exceeds the remaining DMEs by 3 - 3.6-fold, except for DME(8) and DME(10), which have values of kcat/Oxy only 1.7-fold slower.DME(8), the carba analogue of GLM(4), likely binds the two ammonium protons individually with the two oxygens.DME(10) behaves similarly.GLM(4) catalysis of butylaminolysis identifies -(CH2OCH2)4- as an optimal size.DME(8) catalysis confirms this size, although the two catalysts stabilize the two-proton ammonium ion differently.GLM(4) catalyzes butylaminolysis by forming two bifurcated hydrogen bonds.This suggested structure defines the size of the ammonium ion, which agrees with X-ray structural studies of polyether-ammonium complexes.Mechanistic proposals of butylaminolysis of aryl esters require such an ion.The results of this study confirm the stucture of the ion in the rate-limiting step.This building-block approach is a method for "fingerprinting" ammonium ions in transition structures of ionogenic reactions.

Kinetic Resolution of Nearly Symmetric 3-Cyclohexene-1-carboxylate Esters Using a Bacterial Carboxylesterase Identified by Genome Mining

Dou, Zhe,Chen, Xuanzao,Niwayama, Satomi,Xu, Guochao,Ni, Ye

, p. 3043 - 3047 (2021)

A new bacterial carboxylesterase (CarEst3) was identified by genome mining and found to efficiently hydrolyze racemic methyl 3-cyclohexene-1-carboxylate (rac-CHCM) with a nearly symmetric structure for the synthesis of (S)-CHCM. CarEst3 displayed a high substrate tolerance and a stable catalytic performance. The enantioselective hydrolysis of 4.0 M (560 g·L-1) rac-CHCM was accomplished, yielding (S)-CHCM with a >99% ee, a substrate to catalyst ratio of 1400 g·g-1, and a space-time yield of 538 g·L-1·d-1.

Isomer of linker for NU-1000 yields a newshe-type, catalytic, and hierarchically porous, Zr-based metal-organic framework

Lu, Zhiyong,Wang, Rui,Liao, Yijun,Farha, Omar K.,Bi, Wentuan,Sheridan, Thomas R.,Zhang, Kun,Duan, Jiaxin,Liu, Jian,Hupp, Joseph T.

, p. 3571 - 3574 (2021)

The well-known MOF (metal-organic framework) linker tetrakis(p-benzoate)pyrene (TBAPy4?) lacks steric hindrance between its benzoates. Changing the 1,3,6,8-siting of benzoates in TBAPy4?to 4,5,9,10-siting introduces substantial steric hindrance and, in turn, enables the synthesis of a new hierarchically porous,she-type MOF Zr6(μ3-O)4(μ3-OH)4(C6H5COO)3(COO)3(TBAPy-2)3/2(NU-601), where TBAPy-24?is the 4,5,9,10 isomer of TBAPy4?.NU-601shows high catalytic activity for degradative hydrolysis of a simulant for G-type fluoro-phosphorus nerve agents.

Bacillus subtilis spore coat protein LipC is a phospholipase B

Masayama, Atsushi,Kato, Shiro,Terashima, Takuya,Molgaard, Anne,Hemmi, Hisashi,Yoshimura, Tohru,Moriyama, Ryuichi

, p. 24 - 30 (2010)

In Bacillus subtilis, the germination-related lipase LipC is located in the spore coat, and mutant spores are defective in L-alanine-stimulated germination. To determine the physiological role of LipC, the recombinant LipC expressed in Escherichia coli wa

Acceleration of o-iodosobenzoate-catalyzed hydrolysis of p-nitrophenyl diphenyl phosphate by cationic polymer colloids

Lee, Jeng-Jong,Ford, Warren T.

, p. 3753 - 3759 (1994)

Cross-linked polystyrene latexes containing (styrylmethyl)trialkylammonium chloride repeat units greatly accelerate the o-iodosobenzoate (IBA) catalyzed hydrolysis of p-nitrophenyl diphenyl phosphate (PNPDPP). The half-life of PNPDPP is as short as 3 s wi

A mild desilylation of phenolic tert-butyldimethylsilyl ethers using in situ generated tetraethylammonium superoxide

Pandey, Surabhi,Shukla, Ajay K.,Raghuvanshi, Raghvendra S.

, p. 809 - 811 (2021)

Desilylation of phenolic tert-butyldimethylsilyl ethers has been achieved under the mild reaction conditions of in situ generated tetraethylammonium superoxide, at room temperature. (Figure presented.).

Rational design of a transition state analogue with picomolar affinity for pseudomonas aeruginosa PvdQ, a siderophore biosynthetic enzyme

Clevenger, Kenneth D.,Wu, Rui,Er, Joyce A. V.,Liu, Dali,Fast, Walter

, p. 2192 - 2200 (2013)

The Pseudomonas aeruginosa enzyme PvdQ can process different substrates involved in quorum-sensing or in siderophore biosynthesis. Substrate selectivity was evaluated using steady-state kinetic constants for hydrolysis of N-acyl-homoserine lactones (HSLs) and p-nitrophenyl fatty acid esters. PvdQ prefers substrates with alkyl chains between 12 and 14 carbons long that do not bear a 3-oxo substitution and is revealed here to have a relatively high specificity constant for selected N-acyl-HSLs (kcat/KM = 105 to 106 M-1 s-1). However, endogenous P. aeruginosa N-acyl-HSLs are ≥100-fold disfavored, supporting the conclusion that PvdQ was not primarily evolved to regulate endogenous quorum-sensing. PvdQ plays an essential biosynthetic role for the siderophore pyoverdine, on which P. aeruginosa depends for growth in iron-limited environments. A series of alkylboronate inhibitors was found to be reversible, competitive, and extremely potent (Ki ≥ 190 pM). A 1.8 A X-ray structure shows that 1-tridecylboronic acid forms a monocovalent bond with the N-terminal β-chain Ser residue in the PvdQ heterodimer, mimicking a reaction transition state. This boronic acid inhibits growth of P. aeruginosa in iron-limited media, reproducing the phenotype of a genetic pvdQ disruption, although co-administration of an efflux pump inhibitor is required to maintain growth inhibition. These findings support the strategy of designing boron-based inhibitors of siderophore biosynthetic enzymes to control P. aeruginosa infections.

Biodegradation of organophosphorus compounds predicted by enzymatic process using molecular modelling and observed in soil samples through analytical techniques and microbiological analysis: A comparison

Cardozo, Monique,De Almeida, Joyce S.F.D.,De A Cavalcante, Samir F.,Salgado, Jacqueline R.S.,Gon?alves, Arlan S.,Fran?a, Tanos C.C.,Kuca, Kamil,Bizzo, Humberto R.

, (2020)

Organophosphorus compounds (OP) are chemicals widely used as pesticides in different applications such as agriculture and public health (vector control), and some of the highly toxic forms have been used as chemical weapons. After application of OPs in an

Direct Conversion of Haloarenes to Phenols under Mild, Transition-Metal-Free Conditions

Fier, Patrick S.,Maloney, Kevin M.

, p. 2244 - 2247 (2016)

A high-yielding and practical method for the synthesis of phenols from electron-deficient haloarenes and heteroarenes has been developed. The products are formed from acetohydroxamic acid as the hydroxide source via a novel SNAr reaction/Lossen rearrangement sequence. Notably, these reactions employ inexpensive and air-stable reagents, require no special handling, occur under mildly basic conditions, and form products in high yields in the presence of electrophilic and protic functionality. The utility of this methodology is demonstrated by the high-yielding hydroxylation of two base-sensitive complex substrates.

Enantioselective hydrolysis of rasemic naproxen methyl ester with sol-gel encapsulated lipase in the presence of sporopollenin

Yilmaz, Elif,Sezgin, Mehmet,Yilmaz, Mustafa

, p. 162 - 168 (2010)

Sporopollenin is a natural polymer obtained from Lycopodium clavatum, which is highly stable with constant chemical structure and has high resistant capacity to chemical attack. In this study, the Candida rugosa lipase (CRL) was encapsulated within a chemically inert sol-gel support prepared by polycondensation with tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) in the presence and absence of sporopollenin and activated sporopollenin as additive. The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP), and the enantioselective hydrolysis of rasemic Naproxen methyl ester that was studied in aqueous buffer solution/isooctane reaction system. The results indicated that the sporopollenin based encapsulated lipase particularly had higher conversion and enantioselectivity compared to the sol-gel free lipase. In this study, excellent enantioselectivity (E > 400) has been noticed for most lipase preparations (E = 166 for the free enzyme) with an ee value ~98% for S-Naproxen. Moreover, (S)-Naproxen was recovered from the reaction mixture with 98% optical purity.

Purification and characterization of an esterase involved in cellulose acetate degradation by Neisseria sicca SB

Moriyoshi, Kunihiko,Ohmoto, Takashi,Ohe, Tatsuhiko,Sakai, Kiyofumi

, p. 1708 - 1713 (1999)

An esterase catalyzing the hydrolysis of acetyl ester moieties in cellulose acetate was purified 1,110-fold to electrophoretic homogeneity from the culture supernatant of Neisseria sicca SB, which can assimilate cellulose acetate as the sole carbon and en

Geminal alkylammonium surfactants: Aggregation properties and catalytic activity

Mirgorodskaya,Kudryavtseva,Pankratov,Lukashenko,Rizvanova,Konovalov

, p. 1625 - 1631 (2006)

Geminal alkylammonium surfactants containing a hexamethylene spacer show a specific behavior, namely, a catalytic effect at low concentrations of the detergent in the system. The critical micellization concentrations of these surfactants are by an order o

Assessing biocatalysis using dihydrolevoglucosenone (Cyrene) as versatile bio-based (co)solvent

Guajardo, Nadia,Domínguez de María, Pablo

, (2020)

An emerging biogenic aprotic solvent is the cellulose-derived dihydrolevoglucosenone, or 6,8-dioxabicyclooctanone (Cyrene). This paper explores the use of Cyrene in lipase-catalyzed biotransformations, both in aqueous solutions – as co-solvent – as well a

Inhibition of some hepatic glycosidases by the diseco nucleoside, 4-amino-3-(D-glucopentitol-1-yl)-5-mercapto-1,2,4-triazole and its 3-methyl analog.

Balbaa, Mahmoud,Mansour, Hamdi,El-Sawy, Hany,El-Ashry, El-Sayed H

, p. 695 - 708 (2002)

The in vivo and in vitro effects of 4-amino-3-(D-glucopentitol-1-yl)-5-mercapto-1,2,4-triazole and its 3-methyl analogue on alpha- and beta-glucosidases, beta-glucuronidase as well as alpha-amylase have been investigated. alpha-Glucosidase is the enzyme t

New fluorogenic substrate for the first continuous steroid sulfatase assay

Bilban, Melitta,Billich, Andreas,Auer, Manfred,Nussbaumer, Peter

, p. 967 - 969 (2000)

The screening for new inhibitors of steroid sulfatase requires an efficient test system. To overcome the shortcomings of the available discontinuous fluorimetric assay, several coumarin-type compounds were investigated as potential new substrates. 3,4-Benzocoumarin 7-O-sulfate was found to have appropriate substrate properties for the establishment of the first direct continuous assay of steroid sulfatase. (C) 2000 Elsevier Science Ltd. All rights reserved.

On the Mechanism of Oxidation of p-Nitrosophenol by Nitric Acid. A Labelling Study shows the Proposed Nitrodenitrosation Mechanism to be Untenable.

Ross, David S.,Malhotra, Ripudaman,Ogier, Walter C.

, p. 1353 - 1354 (1982)

Oxidation of p-nitrosophenol by 15N-labelled nitric acid in 34percent sulphuric acid (4.4 M) did not produce labelled p-nitrophenol, thereby showing the nitrodenitrosation scheme of Bazanova and Stotskii to be untenable; furthermore, the order of the oxid

Ligand replacement induced chemiluminescence for selective detection of an organophosphorus pesticide using bifunctional Au-Fe3O4 dumbbell-like nanoparticles

Zhang, Jian,Wang, Jianping,Yang, Liang,Liu, Bianhua,Guan, Guijian,Jiang, Changlong,Zhang, Zhongping

, p. 15870 - 15873 (2014)

A facile ligand replacement induced chemiluminescence method is developed for selective detection of the organophosphorus pesticide parathion-methyl based on the use of bifunctional Au-Fe3O4 dumbbell-like nanoparticles to overcome th

REMARKABLE CATALYTIC ACTIVITY OF 2-HYDROXYMETHYLIMIDAZOLE-Zn(II) COMPLEXES IN THE HYDROLYSIS OF p-NITROPHENYL PICOLINATE

Eiki, Toshio,Kawada, Shuji,Matsushima, Kazumi,Mori, Mikio,Tagaki, Waichiro

, p. 997 - 1000 (1980)

The zinc complexes of 2-hydroxymethylimidazole derivatives were found to be remarkably active catalysts for the hydrolysis of p-nitrophenyl picolinate.For example, 2-hydroxymethylimidazole is much more active than the 4-hydroxymethyl isomer, and N-benzyl-

Novel catalytic effects in ester aminolysis in chlorobenzene

Basilio, Nuno,Garcia-Rio, Luis,Leis, J. Ramon,Mejuto, Juan C.,Perez-Lorenzo, Moises

, p. 3817 - 3819 (2005)

The mechanism of glyme catalyzed ester aminolysis in chlorobenzene should be modified by including a new reaction pathway that shows a first-order dependence on the concentration of the phase transfer catalyst and a second-order dependence on butylamine.

Zeolite H-Y-supported copper(II) nitrate: A simple and effective solid-supported reagent for nitration of phenols and their derivatives

Lalitha,Sivakumar

, p. 1745 - 1752 (2008)

Highly regiospecific mononitration of phenols and substituted phenols is accomplished by employing copper(II) nitrate supported on a catalytic amount of zeolite H-Y in a solid state. Copyright Taylor & Francis Group, LLC.

Benzoate Surfactants for Enhancing the Activity of Lipoprotein Lipase from Burkholderia Species in Organic Solvent

Oh, Yeonock

, p. 1093 - 1097 (2019)

Two benzoate surfactants were synthesized and examined as the additives for enhancing the activity of a lipoprotein lipase from Burkholderia species (BSLPL) in organic solvent. It was found that the benzoate surfactants enhanced the turnover number (kcat) by four orders of magnitude and the catalytic efficiency (kcat/Km) by three orders of magnitude. These results strongly suggest that the favorable interaction between the aromatic rings of surfactant tails and the hydrophobic residues around the active site of enzyme may help BSLPL maintain highly active open conformation in organic solvent.

Aromatic nitration under neutral conditions using N-bromosuccinimide/ silver(I) nitrate

Nowrouzi, Najmeh,Mehranpour, Abdol Mohammad,Bashiri, Elham,Shayan, Zohre

, p. 4841 - 4842 (2012)

The use of N-bromosuccinimide and silver nitrate as a convenient reagent system for the nitration of aromatic compounds under neutral and environmentally safer reaction conditions is described.

Characterization of transition states in dichloro(1,4,7-triazacyclononane)copper(II)-catalyzed activated phosphate diester hydrolysis

Deal, Kim A.,Hengge, Alvan C.,Burstyn, Judith N.

, p. 1713 - 1718 (1996)

The reaction mechanism for Cu[9]aneN3CI2-catalyzed hydrolysis of ethyl 4-nitrophenyl phosphate was probed using kinetic isotope effects and isotope exchange experiments. The solvent deuterium isotope effect ((D)k = 1.14), combined wi

Catalytic hydrolysis of phosphate esters by metallocomplexes of 1,10-phenanthroline derivatives in micellar solution

Weijnen, John G. J.,Engbersen, Johan F. J.

, p. 351 - 357 (1993)

Divalent metal-ion complexes of 2,9-bis-1,10-phenanthroline (C12Phen-MII) in neutral Brij 35 micelles catalyse the hydrolysis of various phosphate triesters, diesters and monoesters.The catalytic activity of C12Phen-MII has been compared with that of the metal-ion complexes of its water-soluble counterpart 2,9-bis-1,10-phenanthroline (C1Phen-MII).Saturation kinetics provide evidence for preliminary formation of ligand-MII-phosphate ester complexes, which decay to products.The hydroysis of diphenyl 4-nitrophenyl phosphate (1b) coordinated to C12Phen-ZnII proceeds 8700 times faster than the hydrolysis of 1b in the absence of metallocatalyst.Kinetic studies indicate that phosphate triesters containing a metal-ion-binding site in close proximity to the phosphoryl bond, i.e., diphenyl 5-nitro-2-pyridyl phosphate (2b) and diphenyl 5-nitro-8-quinolyl phosphate (3), are hydrolysed by the same mechanism as 1b.

Phthalocyanine Zinc-catalyzed Hydroxylation of Aryl Boronic Acids under Visible Light

Luo, Dong-Ping,Huang, Yang-Feng,Hong, Xiao-Yi,Chen, Dingben,Li, Guo-Xing,Huang, Xiao-Bo,Gao, Wen-Xia,Liu, Miao-Chang,Zhou, Yun-Bing,Wu, Hua-Yue

, p. 961 - 964 (2019)

A visible-light-promoted aerobic oxidative hydroxylation of boronic acids using phthalocyanine zinc as an easily available photosensitizer has been developed. It provided a direct access to synthesize aliphatic alcohols and phenols from boronic acids. The advantages of this approach included the low catalyst loading (0.5 mol%), high efficient, the use of O2 as an oxygen source, wide substrate range, the simple operational process, and mild conditions. (Figure presented.).

Chelation-controlled selectivity in the clay-catalyzed deprotection of phenolic methoxy methyl ethers

Deville,Behar

, p. 4097 - 4098 (2001)

-

A new non-metal heterogeneous catalyst for the activation of hydrogen peroxide: A perfluorinated ketone attached to silica for oxidation of aromatic amines and alkenes

Neimann,Neumann

, p. 487 - 488 (2001)

A silane functionalized by octafluoroacetophenone was polymerized by the sol-gel method to form an insoluble silicate with perfluoroketone pendants; the silicate was used as a heterogeneous catalyst for the activation of aqueous hydrogen peroxide and the oxidation of aromatic amines and alkenes.

Biochemical and molecular analysis of carboxylesterase-mediated hydrolysis of cocaine and heroin

Hatfield,Tsurkan,Hyatt,Yu,Edwards,Hicks,Wadkins,Potter

, p. 1916 - 1928 (2010)

Background and purpose: Carboxylesterases (CEs) metabolize a wide range of xenobiotic substrates including heroin, cocaine, meperidine and the anticancer agent CPT-11. In this study, we have purified to homogeneity human liver and intestinal CEs and compared their ability with hydrolyse heroin, cocaine and CPT-11. Experimental approach: The hydrolysis of heroin and cocaine by recombinant human CEs was evaluated and the kinetic parameters determined. In addition, microsomal samples prepared from these tissues were subjected to chromatographic separation, and substrate hydrolysis and amounts of different CEs were determined. Key results: In contrast to previous reports, cocaine was not hydrolysed by the human liver CE, hCE1 (CES1), either as highly active recombinant protein or as CEs isolated from human liver or intestinal extracts. These results correlated well with computer-assisted molecular modelling studies that suggested that hydrolysis of cocaine by hCE1 (CES1), would be unlikely to occur. However, cocaine, heroin and CPT-11 were all substrates for the intestinal CE, hiCE (CES2), as determined using both the recombinant protein and the tissue fractions. Again, these data were in agreement with the modelling results. Conclusions and implications: These results indicate that the human liver CE is unlikely to play a role in the metabolism of cocaine and that hydrolysis of this substrate by this class of enzymes is via the human intestinal protein hiCE (CES2). In addition, because no enzyme inhibition is observed at high cocaine concentrations, potentially this route of hydrolysis is important in individuals who overdose on this agent.

Characterization of a recombinant β-xylosidase of GH43 family from Bacteroides ovatus strain ATCC 8483

Zhou, Andong,Hu, Yanbo,Li, Jingjing,Wang, Weiyang,Zhang, Mengshan,Guan, Shuwen

, p. 46 - 52 (2020)

A novel β-1,4-xylosidase was identified from the genome of Bacteroides ovatus strain ATCC 8483 and overexpressed in Escherichia coli BL21 (DE3) cells. The molecular weight of recombinant enzyme named BoXyl43A was calculated to be 37.1 kDa. Using p-nitrophenyl-β-D-xylopyranoside (pNPβXyl) as substrate, BoXyl43A was most active at pH 7.0 and 35 °C. The enzyme could be activated by Mg2+ and Mn2+. The Km and Vmax of BoXyl43A against pNPβXyl were 1.71 ± 0.21 mM, 7.41 ± 0.81 μmol/min/mg, respectively. BoXyl43A hydrolyzed xylooligosaccharide to produce D-xylose as main product, indicating that BoXyl43A acted as an exo-β-1,4-xylosidase. The mixture of BoXyl43A and PoAbf62A (α-L-arabinofuranosidase) exhibited significant synergistic effects on the degradation of arabinoxylan. Therefore, BoXyl43A would be a useful tool to degrade hemicellulose.

Telomers and cotelomers of biological and biomedical interest. VI. The catalytic activity of telomers derived from tris(hydroxymethyl)acrylamidomethane

Boyer,Lamaty,Moussamou-Missima,Pavi,Pucci,Roque

, p. 2415 - 2426 (1992)

Telomers derived from Tris-(hydroxymethyl)-acrylamidomethane (TAC) were investigated with respect to their catalytic properties on the base-catalyzed hydrolysis of para-nitrophenyl esters. In the presence of a carbonate buffer, TAC detergents enhance the

Molecular cloning, purification, and biochemical characterization of a novel pyrethroid-hydrolyzing esterase from Klebsiella sp. strain ZD112

Wu, Pei C.,Liu, Yu H.,Wang, Zhuo Y.,Zhang, Xiao Y.,Li, He,Liang, Wei Q.,Luo, Na,Hu, Ji M.,Lu, Jia Q.,Luan, Tian G.,Cao, Li X.

, p. 836 - 842 (2006)

The gene encoding pyrethroid-hydrolyzing esterase (EstP) from Klebsiella sp. strain ZD112 was cloned into Escherichia coli and sequenced. A sequence analysis of the DNA responsible for the esfP gene revealed an open reading frame of 1914 bp encoding for a protein of 637 amino acid residues. No similarities were found by a database homology search using the nucleotide and deduced amino acid sequences of the esterases and lipases. EstP was heterologously expressed in E. coli and purified. The molecular mass of the native enzyme was approximately 73 kDa as determined by gel filtration. The results of sodium dodecyl sulfate - polyacrylamide gel electrophoresis and the deduced amino acid sequence of EstP indicated molecular masses of 73 and 73.5 kDa, respectively, suggesting that EstP is a monomer. The purified EstP not only degraded many pyrethroid pesticides and the organophosphorus insecticide malathion, but also hydrolyzed ρ-nitrophenyl esters of various fatty acids, indicating that EstP is an esterase with broad substrates. The Km for trans- and cis-permethrin and kcat/Km values indicate that EstP hydrolyzes both these substrates with higher efficiency than the carboxylesterases from resistant insects and mammals. The catalytic activity of EstP was strongly inhibited by Hg2+, Ag+, and ρ-chloromercuribenzoate, whereas a less pronounced effect (3-8% inhibition) was observed in the presence of divalent cations, the chelating agent EDTA, and phenanthroline.

Catalysis in Ester Aminolysis in Aprotic Solvents. The Amine-catalysed Reaction of Imidazole with 4-Nitrophenyl Trifluoroacetate in Aqueous Acetonitrile

Neuvonen, Helmi

, p. 2051 - 2054 (1988)

The imidazolysis of 4-nitrophenyl trifluoroacetate has been investigated in aqueous acetonitrile containing 0.56 mol dm-3 of water.The reaction is found to be general base-catalysed by pyridines and 1-methylimidazole.The catalytic abilities of

β-Glucosidase Activity in the Rat Small Intestine toward Quercetin Monoglucosides

Ioku, Kana,Pongpiriyadacha, Yutana,Konishi, Yotaro,Takei, Yoko,Nakatani, Nobuji,Terao, Junji

, p. 1428 - 1431 (1998)

In order to evaluate the positional specificity for a glucoside group in the hydrolysis of flavonoid glucosides in the rat small intestine, β-glucosidase activity was measured with the quercetin monoglucosides, quercetin-3-O-β-D-glucopyranoside (Q3G), quercetin-4′-O-β-D-glucopyranoside (Q4′G) and quercetin-7-O-β-D-glucopyranoside (Q7G), as well as with quercetin-3-O-rutinoside (rutin) and p-nitrophenyl-β-D-glucopyranoside (NPG) by using the HPLC technique. Enzymes were prepared from rat small intestinal mucosa of the duodenum, jejunum and ileum, among which the enzyme activity of the jejunum was highest for all the glycosides tested. Q4′G was the richest substrate for a β-glucosidase solution among these glycosides, while rutin and NPG were both poor substrates. This suggests that dietary flavonoid glucosides are primarily hydrolyzed and liberated aglycones in the jejunum.

α-Rhamnosidase activity in the marine isolate Novosphingobium sp. PP1Y and its use in the bioconversion of flavonoids

Izzo, Viviana,Tedesco, Pietro,Notomista, Eugenio,Pagnotta, Eduardo,Di Donato, Alberto,Trincone, Antonio,Tramice, Annabella

, p. 95 - 103 (2014)

Crude protein extracts of Novosphingobium sp. PP1Y, a microorganism isolated from polluted marine waters in Pozzuoli (Italy), were analyzed for the presence of glycosidase activities. Particular attention was devoted to a α-L-rhamnosidase activity able to

THE EFFECT OF A LIQUID CRYSTAL MEDIUM ON THE DECOMPOSITION OF p-NITROPHENYL DIMETHYLTHIOPHOSPHATE

Bakeeva, R. F.,Bel'skii, V. E.,Kudryavtseva, L. A.,Dmitrieva, G. V.,Ivanov, B. E.

, p. 1048 - 1050 (1990)

The lamellar liquid crystal meso phase formed in the cetyltrimethylammonium bromide - 1-hexanol - water system assists the reaction of p-nitrophenyl dimethyl thiophosphonate with a charged nucleophile (hexanolate anion) and uncharged nucleophile (ethylene

Determinants for substrate specificity of the bacterial PP2C protein phosphatase tPphA from Thermosynechococcus elongatus

Su, Jiyong,Forchhammer, Karl

, p. 694 - 707 (2013)

Members of the Mg2+- or Mn2+-dependent protein phosphatases/PP2C-like serine/threonine phosphatases (PPM/PP2C) are abundant and widely distributed in prokaryotes and eukaryotes, where they regulate diverse signal transduction pathway

Cyclodextrin derivatives with cyanohydrin and carboxylate groups as artificial glycosidases

Ortega-Caballero, Fernando,Bols, Mikael

, p. 650 - 658 (2006)

Two cyclodextrin derivatives (1 and 2) were prepared in an attempt to create glycosidase mimics with a general acid catalyst and a nucleophilic carboxylate group. The catalysts 1 and 2 were found to catalyse the hydrolysis of 4-nitrophenyl β-D-glucopyrano

Dediazoniation of 4-nitrobenzenediazonium ions in acidic MeOH/H 2O mixtures: Role of acidity and MeOH concentration on the formation of transient diazo ethers that initiate homolytic dediazoniation

Pazo-Llorente, Roman,Maskill, Howard,Bravo-Diaz, Carlos,Gonzalez-Romero, Elisa

, p. 2201 - 2209 (2006)

We have investigated the dediazoniation of 4-nitrobenzene-diazonium (4NBD) ions in MeOH/H2O mixtures under acidic conditions at 50°C employing a combination of spectrophotometric and chromatographic techniques. The kinetic behaviour is quite co

The novel usage of thiourea nitrate in aryl nitration

Meng, Ge,Zheng, Mei-Lin,Zheng, A-Qun,Wang, Mei,Shi, Juan

, p. 87 - 89 (2014)

Thiourea nitrate (TN) was easily prepared from thiourea and nitric acid to explore its use as a new nitration reagent. Nitrations of various aromatic compounds utilizing TN in concentrated sulfuric acid were studied. TN could convert aromatic compounds to the corresponding nitrated derivatives with various abnormal yields under mild conditions. The results suggested that the reaction mechanism might be different from those of traditional nitration reagents.

Cytosol-mimetic chemistry: Kinetics of the trypsin-catalyzed hydrolysis of p-nitrophenyl acetate upon addition of polyethylene glycol and N-tert-butyl acetoacetamide

Asaad, Nabil,Engberts, Jan B. F. N.

, p. 6874 - 6875 (2003)

The sensitivity of an enzyme to its environment has provoked much interest both for its immediate relevance to biochemistry and for the use of enzymes in chemical synthesis. The intercellular or extracellular environment in which an enzyme naturally opera

Efficient dealkylation of aryl alkyl ethers catalyzed by Cu2O

Liu, Lingxian,Li, Zengguang,Chen, Changjun,Li, Huanrong,Xu, Lijin,Yu, Zhiyong

, p. 2447 - 2453 (2018)

An efficient protocol for dealkylation of aryl alkyl ethers under the catalysis of inexpensive and easily reusable Cu2O has been described. The phenol products were obtained in high yields, and a range of functional groups were well tolerated. The choice of solvent is critical to the catalysis, and CH3OH proved to be the optimal choice. Mechanistic investigations showed that this reaction possibly proceeds via a single-electron transfer (SET) process.

Synthesis of fluoroalkyl end-capped co-oligomers containing 8-hydroxyquinolyl segments and application to oligomer-catalyzed solvolysis reactions

Sawada,Hata,Kawasaki,Kawase,Fujimori

, p. 59 - 62 (2001)

New fluoroalkyl end-capped co-oligomers containing 8-hydroxyquinolyl segments were prepared by the reactions of fluoroalkyl end-capped co-oligomers bearing isocyanato groups. The solvolysis of p-nitrophenyl propaonate (PNP) in the presence of these fluori

Influence of gold nanoparticles of varying size in improving the lipase activity within cationic reverse micelles

Maiti, Subhabrata,Das, Dibyendu,Shome, Anshupriya,Das, Prasanta Kumar

, p. 1941 - 1950 (2010)

Herein, we report the effect of gold nanoparticles (GNPs) in enhancing lipase activity in reverse micelles of cetyltrimethylammonium bromide (CTAB)/water/isooctane/n-hexanol. The size and concentration of the nanoparticles were varied and their specific r

Preferential modification of CyaA-hemolysin by CyaC-acyltransferase through the catalytic Ser30-His33 dyad in esterolysis of palmitoyl-donor substrate devoid of acyl carrier proteins

Yentongchai, Mattayaus,Thamwiriyasati, Niramon,Imtong, Chompounoot,Li, Hui-Chun,Angsuthanasombat, Chanan

, (2020)

We previously demonstrated that the ~130-kDa CyaA-hemolysin domain (CyaA-Hly) from Bordetella pertussis co-expressed with CyaC-acyltransferase in Escherichia coli was acylated at Lys983 and thus activated its hemolytic activity. Here, attempts

Lanthanide Cleavage of Phosphodiester Liposomes

Moss, Robert A.,Park, Byeong D.,Scrimin, Paolo,Ghirlanda, Giovanna

, p. 1627 - 1628 (1995)

Cleavages of a liposomal phosphodiester by Eu3+ or La3+/H2O2 are attended by 50 to 70-fold rate accelerations relative to a non-aggregated model phosphodiester, whilst trans-bilayer Eu3+ transport can be mediated by an hydrophobic ethylene diamine derivat

α-Glucosidase inhibitory and anti-inflammatory activities of dammarane triterpenoids from the leaves of Cyclocarya paliurus

Deng, Shengping,Hao, Lili,Huang, Xishan,Huang, Yan,Li, Chenguo,Li, Jun,Liang, Cheng-qin,Liu, Wei,Su, Shanshan,Xu, Xia,Yang, Ruiyun,Zhang, Gaorong,Zhou, Dexiong

, (2021)

Diabetes mellitus is caused by chronic inflammation and affects millions of people worldwide. Cyclocarya paliurus leaves have been widely used in traditional folk tea as a remedy for diabetes, but the antidiabetic constituents remain to be further studied. The α-glucosidase inhibitory and anti-inflammatory activities were examined to evaluate their effects on diabetes mellitus, and bioassay-guided separation of C. paliurus leaves led to the identification of twenty dammarane saponins, including eleven new dammarane saponins (1–11). The structures of the isolates were elucidated by spectroscopic methods. Bioactivity assay results showed that compounds 1 and 2 strongly inhibited α-glucosidase activity, with IC50 values ranging from 257.74 μM, 282.23 μM, and strongly inhibited the release of NO, with IC50 values of 9.10 μM, 9.02 μM. Moreover, compound 2 significantly downregulated the mRNA expression of iNOS, COX-2, IL-1β, NF-κB, IL-6 and TNF-α in LPS-mediated RAW 264.7 cells and markedly suppressed the protein expression of iNOS, NF-κB/p65, and COX-2. Dammarane glucoside 2 exhibited the strongest α-glucosidase inhibitory and anti-inflammatory activities. In addition, the structure–activity relationships (SARs) of the dammarane saponins were investigated. In summary, C. paliurus leaves showed marked α-glucosidase inhibitory and anti-inflammatory activities, and dammarane saponins are responsible for regulating α-glucosidase, inflammatory mediators, and mRNA and the protein expression of proinflammatory cytokines, which could be meaningful for discovering new antidiabetic agents.

Reactions in Micelles of Cetyltrimethylammonium Hydroxyde. Test of the Pseudophase Model for Kinetics

Bunton, Clifford A.,Gan, Leong-Huat,Moffatt, John R.,Romsted, Laurence S.,Savelli, Gianfranco

, p. 4118 - 4125 (1981)

The rate constants for reactions of OH- with 2,4-dinitrochlorobenzene (DCNB), 2,4-dinitrochloronaphthalene (DNCN), and p-nitrophenyl diphenyl phosphate (pNPDPP) in micellized cetyltrimethylammonium hydroxyde (CTAOH) do not conform to the pseudophase ion-exchanged model.The rate constants do not become constant when substrates are fully micellar bound and increase on addition of NaOH.However, with the more hydrophobic substrates DNCN and pNPDPP we appear to reach limiting rate constants at high or high .These observations can be explained on the assumption that the charge on a CTAOH micelle decreases on addition of OH-, i.e., the concentration of OH- in the micelle increases with increasing -> in the aqueous pseudophase.The rate-surfactant profiles for reactions of DNCN and pNPDPP can be interpreted quantitatively in these terms.For reactions of DNCB the rate data can be interpreted if we assume that added OH- also increasees binding of DNCB to the micelle.

A Zinc(II) Complex of 1,5,9-Triazacyclododecane ([12]aneN3) as a Model for Carbonic Anhydrase

Kimura, Eiichi,Shiota, Takeshi,Koike, Tohru,Shiro, Motoo,Kodama, Mutsuo

, p. 5805 - 5811 (1990)

Among macrocyclic tri- and tetraamines tested, a 12-membered triamine, [12]aneN3, is the most appropriate ligand that mimics the ligand field surrounding ZnII in carbonic anhydrases. In its 1:1 ZnIIL complex, the H2O bound at the fourth coordination site deprotonates with the pKa value of 7.30 at 25°C, I = 0.1 (NaClO4), almost the same value being reported for the ZnII-enzymes. The resulting hydroxo complex is precipitated as a trimer from pH 8 aqueous solution, which with a formula of [ZnIIL(OH)]3(ClO4)3·HClO 4 has been analyzed by X-ray crystal study. The crystals of (11)3·(ClO4)·HClO4, C27H67N9O19CLZn3, are trigonal, space group R3c with six molecules of 11 in the unit cell of dimensions a = 22.103 (1) A?, c = 16.514 (2) A?. Anion binding affinity to the ZnIIL complex is determined by pH titration to have an order of OH- (log K = 6.4) ? CH3COO- (2.6) > SCN- (2.4) > I- (1.6) > Br- (1.5) > F- (0.8), which is almost comparable with the anion inhibition order and magnitude reported for carbonic anhydrase activities. Moreover, like the ZnII-enzymes, the [ZnIIL(OH)]+ species catalyzes methyl acetate hydrolysis and acetaldehyde hydration, where the ZnII-bound OH- commonly acts as a nucleophile to the carbonyl carbons. The plots of these rate constants vs pH in either case show the kinetic pKa values of ZnIIL(OH2) to be nearly the same as the thermodynamically obtained values of 7.3 at 25°C and 7.9 at 0°C. Various outstanding properties of ZnII in enzymes (over other metal ions such as CoIII), which contribute to its biological significance, have been well demonstrated by the present macrocyclic triamine complex behaviors.

Nimbandiolactone-21 and nimbandioloxyfuran, two new 28-norlimonoids from the leaves of Azadirachta indica (Meliaceae)

Nguyen, Nhi Y Thi,Dang, Phu Hoang,Thien Nguyen, Van Truong,Vo, Tuan Trong,Nguyen, Dao Anh Thi,Nguyen, Minh Duc Huu,Dang, Phuc Huu,Tran, Quan Le

, p. 867 - 872 (2019)

From an EtOAc-soluble fraction of the leaves of Azadirachta indica, two new 28-norlimonoids named nimbandiolactone-21 (1) and nimbandioloxyfuran (2), together with nimbandiolactone-23 (3), were isolated. Their relative structures were elucidated based on

Role of hydrophobic residues in the aglycone binding subsite of a GH39 β-xylosidase in alkyl xylosides synthesis

Ochs, Marjorie,Belloy, Nicolas,Dauchez, Manuel,Muzard, Murielle,Plantier-Royon, Richard,Remond, Caroline

, p. 21 - 26 (2013)

The GH39 β-xylosidase from Bacillus halodurans (BhXyl39) was previously reported to catalyze the synthesis of alkyl xylosides from donors such as pNP β-d-xylopyranoside or xylobiose and from aliphatic alcohols acting as acceptors with chain length inferior to five carbons. In the present study, the role played by aromatic residues present in the aglycone binding subsite of BhXyl39 in the hydrolysis and transglycosylation reactions of the enzyme was investigated. In this way, site-directed mutagenesis was carried out in order to highlight the role of three targeted hydrophobic residues F116, F167 and Y284. These residues were replaced by alanine to decrease the steric hindrance or were mutated into serine to evaluate the impact of the presence of a polar residue into the aglycone binding subsite of BhXyl39. Taking into account kinetic parameters and yields of transglycosylation, the function of each mutated residue in the catalytic mechanism was studied. Results concerning transglycosylation reactions in the presence of pentan-1-ol and octan-1-ol indicated that yields of transglycosylation were impacted both by the position and the nature of the mutated residues. These results were consistent with molecular docking performed with both acceptors which notably confirms that among the three targeted residues, F116 represents the most interesting one for mutagenesis to increase the transglycosylation reactions in presence of long chain alcohols.

Functional divergence caused by mutations in an energetic hotspot in ERK2

Taylor, Clinton A.,Cormier, Kevin W.,Keenan, Shannon E.,Earnest, Svetlana,Stippec, Steve,Wichaidit, Chonlarat,Juang, Yu-Chi,Wang, Junmei,Shvartsman, Stanislav Y.,Goldsmith, Elizabeth J.,Cobb, Melanie H.

, p. 15514 - 15523 (2019)

The most frequent extracellular signal-regulated kinase 2 (ERK2) mutation occurring in cancers is E322K (E-K). ERK2 E-K reverses a buried charge in the ERK2 common docking (CD) site a region that binds activators inhibitors and substrates. Little is known

Synthesis, structure and hydrolytic properties of a family of new Zn complexes containing hexaazamacrocyclic ligands

Costas, Miquel,Anda, Carmen,Llobet, Antoni,Parella, Teodor,Evans, Helen Stoeckli,Pinilla, Elena

, p. 857 - 865 (2004)

The synthesis, structure and spectroscopic properties of a family of Zn complexes containing a dinucleating hexaazamacrocyclic ligand (L) and anionic ligands (X) of general formula [Zn2(X)4-n(L)]n+ (1-8; L = H2p, H3p, Me2p

Hydrolysis of nipecotic acid phenyl esters

Gokhale,Crider,Gupte,Wood

, p. 63 - 65 (1990)

The synthesis and anticonvulsant activity of nipecotic acid esters (1a-1f) have been previously reported. It was thought that these prodrug esters underwent hydrolytic conversion to 1 which inhibited GABA uptake, and that both 1 and an intact ester may ha

Photoinduced Hydroxylation of Organic Halides under Mild Conditions

Cai, Yue-Ming,Xu, Yu-Ting,Zhang, Xin,Gao, Wen-Xia,Huang, Xiao-Bo,Zhou, Yun-Bing,Liu, Miao-Chang,Wu, Hua-Yue

, p. 8479 - 8484 (2019)

Presented in this paper is photoinduced hydroxylation of organic halides, providing a mild access to a range of functionalized phenols and aliphatic alcohols. These reactions generally proceed under mild reaction conditions with no need for a photocatalyst or a strong base and show a wide substrate scope as well as excellent functional group tolerance. This work highlights the unique role of NaI that allows a challenging transformation to proceed under mild reaction conditions.

3-(Ethoxycarbonyl)-1-(5-methyl-5-(nitrosooxy)hexyl)pyridin-1-ium cation: A green alternative to tert-butyl nitrite for synthesis of nitro-group-containing arenes and drugs at room temperature

Chaudhary, Renu,Natarajan, Palani,Rani, Neetu,Sakshi,Venugopalan, Paloth

, (2019)

Due to their remarkable properties, task-specific ionic liquids have turned out to be progressively popular over the last few years in the field of green organic synthesis. Herein, for the first time, we report that a new task-specific nitrite-based ionic liquid such as 3-(ethoxycarbonyl)-1-(5-methyl-5-(nitrosooxy)hexyl)pyridin-1-ium bis(trifluoromethanesulfonyl)imides (TS-N-IL) derived from biodegradable ethyl nicotinate indeed acted as an efficient and eco-friendly reagent for the synthesis of highly valuable nitroaromatic compounds and drugs including nitroxynil, tolcapone, niclofolan, flutamide, niclosamide and nitrazepam. The bridging of an ionic liquid with nitrite group not only increases the yield and rate of direct C[sbnd]N bond formation reaction but also allows easy product separation and recyclability of a byproduct. Nonvolatile nature, easy synthesis, merely stoichiometric need and mildness are a portion of the extra focal points of TS-N-IL while contrasted with tert-butyl nitrite an outstanding and highly-flammable reagent utilized largely in organic synthesis.

Organic synthesis in water/carbon dioxide microemulsions

Jacobson,Lee C.T.,Johnston

, p. 1201 - 1206 (1999)

Nucleophilic substitution reactions were performed in H2O/CO2 (w/c) microemulsions formed with an anionic perfluoropolyether ammonium carboxylate (PFPE COO-NH4+) surfactant. These reactions between hydrophilic nucleophiles and hydrophobic substrates were accomplished in an environmentally benign microemulsion without requiring toxic organic solvents or phase transfer catalysts. For the synthesis of benzyl bromide from benzyl chloride and KBr, the yield was an order of magnitude higher in w/c microemulsions versus conventional water-in-oil (w/o) microemulsions. Benzoyl chloride and p-nitrophenyl chloroformate were hydrolyzed in w/c microemulsions with rate constants an order of magnitude faster than those in w/o microemulsions.

Organic reactions and nanoparticle preparation in Co2-induced water/P104/p-xylene microemulsions

Zhang, Rui,Liu, Jun,He, Jun,Han, Buxing,Wu, Weize,Jiang, Tao,Liu, Zhimin,Du, Jimin

, p. 2167 - 2172 (2003)

Nanometer-sized gold particles are synthesized by the reduction of HAuCl4 with KBH4 in the CO2-induced microemulsion of (EO)27(PO)61(EO)27 (P104; EO = ethylene oxide, PO = propylene oxide)/p-xylene/CO2/H2O. The recovery of gold particles from the microemulsion can be easily accomplished by the venting of CO2, while the surfactant remains in the organic phase. The effect of the molar ratio of the reductant to HAuCl4, the concentration of the reactants, and the molar ratio of water to EO segments (W0) in the reverse micelles on the size of the gold particles is studied. The hydrolysis of benzoyl chloride (BzCl) and p-nitrophenyl chloroformate (NPhCl) has also been carried out in the microemulsion. The results show that the observed rate constants kobs of both substrates increase significantly with W0, and that W0 has a larger influence on the hydrolysis of BzCl. The different extents of the influence of W0 on the two reactions can be ascribed to the different reaction mechanisms and the expected changes in nucleophilicity and polarity of water in the reverse micelles.

Prussian Blue/NaNO2 as an Efficient Reagent for the Nitration of Phenols in Aqueous Bisulfate and Acetonitrile Medium: Synthetic and Kinetic Study

Srinivas, Pasnoori,Suresh, Muppidi,Rajanna,Krishnaiah

, p. 209 - 218 (2017)

The reaction kinetics of Prussian blue (PB)/NaNO2 initiated for the nitration of phenols by in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [phenol], [NaNO2], and [PB]. An increase in [KHSO4] accelerated the rate of nitration under otherwise similar conditions. The rate of nitration was faster in the solvent of higher dielectric constant (D). Observed results were in accordance with Amis and Kirkwood plots [log k′ vs. (1/D) and [(D ? 1)/(2D + 1)]. These findings together with the linearity of plots, log k′ versus (vol% of acetonitrile (ACN)) and mole fraction of (nx) ACN, probably indicate the importance of both eloctrostatic and nonelctrostatic forces, solvent–solute interactions during nitration of phenols. Reaction rates accelerated with the introduction of electron-donating groups and retarded with electron-withdrawing groups, which are interpreted by Hammett's theory of linear free energy relationship. Hammett's reaction constant (ρ) is a fairly large negative (ρ 0) value, indicating attack of an electrophile on the aromatic ring. Furthermore, an increase in temperature decreased the reaction constant (ρ) values. This trend was useful in obtaining isokinetic temperature (β) from Exner's plot of ρ versus 1/T. Observed β value (337.8 K) is above the experimental temperature range (303–323 K), indicating that the enthalpy factors are probably more important in controlling the reaction.

Zn(2+) Inclusion Complexes of Endodentate Tripodands as Carbonic Anhydrase-Inspired Artificial Esterases

Jairam, Rick,Potvin, Pierre G.

, p. 4136 - 4141 (1992)

Facile syntheses are reported for three endo-tridentate tris-imidazole podands 1 - 3, two of which also bear basic amino residues, designed to reproduce the active site of carbonic anhydrase.The architecture was tested for the ability to bind Zn(2+) in a

Aminolysis of 4-nitrophenyl esters of phosphorus acids in reversed micelles of 2-hydroxyethyldimethylpentadecylammonium bromide

Tishkova,Kudryavtseva,Bel'skii

, p. 2011 - 2014 (1997)

The reactions of n-cetyl- and n-hexylamines with 4-nitrophenyl esters of tetracoordinated phosphorus acids in chloroform in the presence of 2-hydroxyethyldimethylpentadecyl-ammonium bromide and the influence of the latter on the acid - base equilibrium of

A zinc(II)-included hemicryptophane: Facile synthesis, characterization, and catalytic activity

Makita, Yoshimasa,Sugimoto, Kazuya,Furuyoshi, Kenta,Ikeda, Keisuke,Fujiwara, Shin-Ichi,Shin-Ike, Tsutomu,Ogawa, Akiya

, p. 7220 - 7222 (2010)

A zinc(II)-included hemicryptophane, which has a zinc(II) center embedded in the cavity, was synthesized and characterized. The catalytic activity of the hemicryptophane was tested in the hydrolysis of methyl para-nitrophenyl carbonate (MPC). A direct com

Both hydrolytic and transesterification activities of Penicillium expansum lipase are significantly enhanced in ionic liquid [BMIm][PF6]

Yang, Zhen,Zhang, Kai-Pei,Huang, Ying,Wang, Zhi

, p. 23 - 30 (2010)

Both hydrolytic and transesterification activities of Penicillium expansum lipase (PEL) were investigated in the ionic liquid [BMIm][PF6] as well as in organic solvents such as hexane. The initial rate of PEL-catalyzed hydrolysis of p-nitrophen

An efficient base and H2O2 free protocol for the synthesis of phenols in water and oxygen using spinel CuFe2O4 magnetic nanoparticles

Chutia, Rituparna,Chetia, Bolin

, p. 1925 - 1936 (2020)

An efficient base and H2O2 free protocol was used for the synthesis of phenols from boronic acids using biogenic CuFe2O4 magnetic nanoparticles as catalyst at room temperature in water and oxygen. The catalyst was prepared using the flowers of Lantana camara. The size of the nanoparticles was 4.27 nm. Base free and ligand free protocol, less time, excellent yields, room temperature, biogenic synthesis of the catalyst, use of O2 as an environmentally friendly oxidant are the advantages of the present protocol. The recyclability of the catalyst was for 5 cycles without loss of magnetic property or catalytic activity.

A novel, simple and rapid regeneration of alcohols from their allylic ethers using NaCNBH3/TMSCl

Venkat Rao,Subbash Reddy,Hari Mohan,Iyengar

, p. 3565 - 3568 (2000)

A Novel, Simple and efficient method for the regeneration of alcohols from their allylic ethers using NaCNBH3/TMSCl is described.

Recombinant silicateins as model biocatalysts in organosiloxane chemistry

Dakhili, S. Yasin Tabatabaei,Caslin, Stephanie A.,Faponle, Abayomi S.,Quayle, Peter,De Visser, Sam P.,Wong, Lu Shin

, p. E5285 - E5291 (2017)

The family of silicatein enzymes from marine sponges (phylum Porifera) is unique in nature for catalyzing the formation of inorganic silica structures, which the organisms incorporate into their skeleton. However, the synthesis of organosiloxanes catalyzed by these enzymes has thus far remained largely unexplored. To investigate the reactivity of these enzymes in relation to this important class of compounds, their catalysis of Si-O bond hydrolysis and condensation was investigated with a range of model organosilanols and silyl ethers. The enzymes' kinetic parameters were obtained by a high-throughput colorimetric assay based on the hydrolysis of 4-nitrophenyl silyl ethers. These assays showed unambiguous catalysis with kcat/Km values on the order of 2-50 min-1 μM-1. Condensation reactions were also demonstrated by the generation of silyl ethers from their corresponding silanols and alcohols. Notably, when presented with a substrate bearing both aliphatic and aromatic hydroxy groups the enzyme preferentially silylates the latter group, in clear contrast to nonenzymatic silylations. Furthermore, the silicateins are able to catalyze transetherifications, where the silyl group from one silyl ether may be transferred to a recipient alcohol. Despite close sequence homology to the protease cathepsin L, the silicateins seem to exhibit no significant protease or esterase activity when tested against analogous substrates. Overall, these results suggest the silicateins are promising candidates for future elaboration into efficient and selective biocatalysts for organosiloxane chemistry.

Detection of enzyme activity through catalytic signal amplification with functionalized gold nanoparticles

Bonomi, Renato,Cazzolaro, Alessandro,Sansone, Anna,Scrimin, Paolo,Prins, Leonard J.

, p. 2307 - 2312 (2011)

A cascade of two catalytic events was used to detect enzyme activity: When a peptide substrate acting as an inhibitor for a catalytic gold nanoparticle was hydrolyzed by an enzyme, the catalytic activity of the nanoparticle was restored, and a large amount of a yellow reporter molecule was produced (see picture; S=substrate, P=product). The assay can be made selective for a particular enzyme by changing the inhibitory peptide. (Chemical Equation Presented).

Functionalized surfactant mediated reactions of carboxylate, phosphate and sulphonate esters

Tiwarib, Shuchi,Ghosh, Kallol K.,Marek, Jan,Kuca, Kamil

, p. 519 - 525 (2010)

Nucleophilic reactivity of some functionalized surfactants, i.e. quaternary pyridinium aldoximes towards the hydrolysis of p-nitrophenyl acetate (PNPA), p-nitrophenyl benzoate (PNPB), p-nitrophenyldiphenyl phosphate (PNPDPP) and p-nitrophenyl p-toluene su

POLYPEPTIDES POSSESSING CATALYTIC PROPERTIES

Khalikov, Sh. Kh.,Alieva, S. V.,Valiev, R. V.

, p. 475 - 478 (1984)

The catalytic properties of synthetic polypeptides containing L-amino acids with the sequences H-(His-Glu)n-OH, H-(Ser-Glu)n-OH, H-(His-Tyr)n-OH, and H-(Trp-Glu)n-OH in the hydrolysis of p-NPA (para-nitrophenyl acetate) are considered.The dependences of t

Studies on human prostatic acid phosphatase. III. The effects of alcohols on human erythrocyte acid phosphatase and on human prostatic acid phosphatase

Sawada,Asano,Maruyama,Shinoda,Aoki

, p. 3466 - 3472 (1980)

-

The role of conserved arginine residue in loop 4 of glycoside hydrolase family 10 xylanases

Nishimoto, Mamoru,Kitaoka, Motomitsu,Fushinobu, Shinya,Hayashi, Kiyoshi

, p. 904 - 910 (2005)

An arginine residue in loop 4 connecting β strand 4 and α-helix 4 is conserved in glycoside hydrolase family 10 (GH10) xylanases. The arginine residues, Arg204 in xylanase A from Bacillus halodurans C-125 (XynA) and Arg196 in xylanas

Cross-Linked Micelles with Enzyme-Like Active Sites for Biomimetic Hydrolysis of Activated Esters

Hu, Lan,Zhao, Yan

, (2017)

Enzymes have substrate-tailored active sites with optimized molecular recognition and catalytic features. Although many different platforms have been used by chemists to construct enzyme mimics, it is challenging to tune the structure of their active site

Biochemical characterization of the cutinases from Thermobifida fusca

Chen, Sheng,Su, Lingqia,Billig, Susan,Zimmermann, Wolfgang,Chen, Jian,Wu, Jing

, p. 121 - 127 (2010)

Thermobifida fusca produces two cutinases which share 93% identity in amino acid sequence. In the present study, we investigated the detailed biochemical properties of T. fusca cutinases for the first time. For a better comparison between bacterial and fungal cutinases, recombinant Fusarium solani pisi cutinase was subjected to the similar analysis. The results showed that both bacterial and fungal cutinases are monomeric proteins in solution. The bacterial cutinases exhibited a broad substrate specificity against plant cutin, synthetic polyesters, insoluble triglycerides, and soluble esters. In addition, the two isoenzymes of T. fusca and the F. solani pisi cutinase are similar in substrate kinetics, the lack of interfacial activation, and metal ion requirements. However, the T. fusca cutinases showed higher stability in the presence of surfactants and organic solvents. Considering the versatile hydrolytic activity, good tolerance to surfactants, superior stability in organic solvents, and thermostability demonstrated by T. fusca cutinases, they may have promising applications in related industries.

Catalytic Hydrolysis of Phosphate Monoesters by Lanthanide(III) Cryptate (2.2.1) Complexes

Oh, Soon Jin,Song, Kyong Hwa,Park, Joon Won

, p. 575 - 576 (1995)

The hydrolysis of 4-nitrophenyl phosphate is catalysed by lanthanide(III) (2.2.1) complexes, and kinetic studies reveal that the europium(III) (2.2.1) chloride (c = 4.0 mmol dm-3) hydrolyses the phosphate monoester at an enhanced rate (kp1

Molecular cloning of a thermo-alkaliphilic lipase from Bacillus subtilis DR8806: Expression and biochemical characterization

Emtenani, Shirin,Asoodeh, Ahmad,Emtenani, Shamsi

, p. 1679 - 1685 (2013)

A thermo-alkaliphilic lipase from Bacillus subtilis DR8806 was functionally expressed as an N-terminal 6xHis-tagged recombinant enzyme in Escherichia coli BL21 using pET-28a(+) expression vector. Sequence analysis revealed an open reading frame of 639 bp

Regulation of the hydrolytic activity of Mg2+-dependent phosphatase models by intramolecular NH···O hydrogen bonds

Okamura, Taka-Aki,Furuya, Ryosuke,Onitsuka, Kiyotaka

, p. 14639 - 14641 (2014)

Magnesium-dependent phosphatase models containing intramolecular NH···O hydrogen bonds were synthesized and structurally characterized by X-ray analysis. The Mg-O bond distances varied with the mode of the hydrogen bonds. 1H NMR spectra in nonp

Immobilization of thermostable β-glucosidase variants on acrylic supports for biocatalytic processes in hot water

Khan, Samiullah,Lindahl, Sofia,Turner, Charlotta,Karlsson, Eva Nordberg

, p. 28 - 38 (2012)

Two variants of the thermostable β-glucosidase TnBgl1A (wt and N221S/P342L) from Thermotoga neapolitana were immobilized on acrylic supports (Eupergit C, Eupergit C250L, and cryogel) and evaluated at conditions close to the boiling point of water. Thermo-

Identification of the acid/base catalyst of a glycoside hydrolase family 3 (GH3) β-glucosidase from Aspergillus niger ASKU28

Thongpoo, Preeyanuch,McKee, Lauren S.,Araújo, Ana Catarina,Kongsaeree, Prachumporn T.,Brumer, Harry

, p. 2739 - 2749 (2013)

Background The commercially important glycoside hydrolase family 3 (GH3) β-glucosidases from Aspergillus niger are anomeric-configuration-retaining enzymes that operate through the canonical double-displacement glycosidase mechanism. Whereas the catalytic nucleophile is readily identified across all GH3 members by sequence alignments, the acid/base catalyst in this family is phylogenetically variable and less readily divined. Methods In this report, we employed three-dimensional structure homology modeling and detailed kinetic analysis of site-directed mutants to identify the catalytic acid/base of a GH3 β-glucosidase from A. niger ASKU28. Results In comparison to the wild-type enzyme and other mutants, the E490A variant exhibited greatly reduced k cat and kcat/Km values toward the natural substrate cellobiose (67,000- and 61,000-fold, respectively). Correspondingly smaller kinetic effects were observed for artificial chromogenic substrates p-nitrophenyl β-d-glucoside and 2,4-dinitrophenyl β-d-glucoside, the aglycone leaving groups of which are less dependent on acid catalysis, although changes in the rate-determining catalytic step were revealed for both. pH-rate profile analyses also implicated E490 as the general acid/base catalyst. Addition of azide as an exogenous nucleophile partially rescued the activity of the E490A variant with the aryl β-glucosides and yielded β-glucosyl azide as a product. Conclusions and general significance These results strongly support the assignment of E490 as the acid/base catalyst in a β-glucosidase from A. niger ASKU28, and provide crucial experimental support for the bioinformatic identification of the homologous residue in a range of related GH3 subfamily members.

A colorimetric substrate for poly(ADP-ribose) polymerase-1, VPARP, and tankyrase-1

Nottbohm, Amanda C.,Dothager, Robin S.,Putt, Karson S.,Hoyt, Mirth T.,Hergenrother, Paul J.

, p. 2066 - 2069 (2007)

(Chemical Equation Presented) Color me yellow: Poly(ADP-ribose) polymerases (PARPs) play a major role in cellular survival and maintenance of energy stores after genotoxic insult. The colorimetric PARP substrate ADP-ribose-pNP can be used to monitor PARP

Reactions within Association Complexes: The Reaction of Imidazole with Substituted Phenyl Acetates in the Presence of Detergents in Aqueous Solution

Pirinccioglu, Necmettin,Zaman, Flora,Williams, Andrew

, p. 2537 - 2543 (2000)

The bimolecular rate constants for reaction of imidazole with phenyl acetates complexed with sodium dodecyl sulfate (SDS) or cetyltrimethylammonium bromide (CTAB) micelles obey Bronsted equations with βlg similar to that of the reaction in aqueous solution. The dissociation constants of ester (KS) and the hypothetical dissociation constant (KTS) of the transition state of the micelle complexes obey Hansch equations with similar sensitivities (p) to π (-0.66 and -0.589 for KS and -0.735 and -0.495 for KTS, respectively). The slopes also indicate that the microsolvation environments associated with the transition state and the complexed ester have aqueous character. The relative values of KTS and KS indicate that the transition state of the reaction of imidazole with ester is more weakly complexed to both micelles than is the reactant ester. Log KTS values are linear functions of log KS for reactions with both CTAB and SDS; the slopes are, respectively, -0.893 and -1.19 consistent with a slightly more "water-like" medium for the transition state than for the site of binding of ester with CTAB-micelle and slightly less for the SDS-micelle. The results for ester and transition state are consistent with the location of the phenyl residue in a hydrophobic region that possesses water molecules. It is concluded that the acetyl group in the complexed transition state is located in an aqueous part of the Stern region, whereas the phenyl residue is in a part of the Stern region that possesses alkane components. The derived kinetic and complexation parameters in these experiments refer to micelles with Stern regions that have been maintained at constant ionic compositions.

Influence of the substituent on selective photocatalytic oxidation of aromatic compounds in aqueous TiO2 suspensions

Palmisano, Giovanni,Addamo, Maurizio,Augugliaro, Vincenzo,Caronna, Tullio,Garcia-Lopez, Elisa,Loddo, Vittorio,Palmisano, Leonardo

, p. 1012 - 1014 (2006)

Experimental results are reported showing that the photocatalytic oxidation of aromatic compounds containing an electron-donor group (EDG) gives rise mainly to ortho- and para-monohydroxy derivatives while in the presence of an electron-withdrawing group (EWG) all the monohydroxy derivatives are obtained. The Royal Society of Chemistry 2006.

Cholesterol esterase activity by in vitro selection of RNA against a phosphate transition-state analogue [9]

Chun, Sung-Min,Jeong, Sunjoo,Kim, Jong-Man,Chong, Byong-Oh,Park, Young-Keun,Park, Hokoon,Yu, Jaehoon

, p. 10844 - 10845 (1999)

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Harnessing thorium(IV) as a catalyst: RNA and phosphate diester cleavage by a thorium(IV) macrocyclic complex

Wang,Choudhary,Vink,Secord,Morrow

, p. 2509 - 2510 (2000)

A robust macrocyclic tetraamide complex of Th(IV) binds phosphate diesters and promotes cleavage of RNA and phosphate diesters at 37 °C in the pH range 5.00-7.90.

Cloning, expression and characterization of a new enantioselective esterase from a marine bacterium Pelagibacterium halotolerans B2T

Wei, Xiaolian,Jiang, Xiawei,Ye, Lidan,Yuan, Shenfeng,Chen, Zhirong,Wu, Min,Yu, Hongwei

, p. 270 - 277 (2013)

An esterase, designated as PE8 (219 aa, 23.19 kDa), was cloned from a marine bacterium Pelagibacterium halotolerans B2T and overexpressed in Escherichia coli Rosetta, resulting an active, soluble protein which constituted 23.1% of the total cell protein content. Phylogenetic analysis of the protein showed it was a new member of family VI lipolytic enzymes. Biochemical characterization analysis showed that PE8 preferred short chain p-nitrophenyl esters (C2-C6), exhibited maximum activity toward p-nitrophenyl acetate, and was not a metalloenzyme. PE8 was an alkaline esterase with an optimal pH of 9.5 and an optimal temperature of 45 C toward p-nitrophenyl acetate. Furthermore, it was found that PE8 exhibited activity and enantioselectivity in the synthesis of methyl (R)-3-(4-fluorophenyl)glutarate ((R)-3-MFG) from the prochiral dimethyl 3-(4-fluorophenyl)glutarate (3-DFG). (R)-3-MFG was obtained in 71.6% ee and 73.2% yield after 36 h reaction under optimized conditions (0.6 M phosphate buffer (pH 8.0) containing 17.5% 1,4-dioxane under 30 C). In addition, PE8 was tolerant to extremely strong basic and high ionic strength solutions as it exhibited high activity even at pH 11.0 in 1 M phosphate buffer. Given its highly soluble expression, alkalitolerance, halotolerance and enantioselectivity, PE8 could be a promising candidate for the production of (R)-3-MFG in industry. The results also demonstrate the potential of the marine environment as a source of useful biocatalysts.

Fries rearrangement in ionic melts

Harjani, Jitendra R.,Nara, Susheel J.,Salunkhe, Manikrao M.

, p. 1979 - 1981 (2001)

1-Butyl-3-methylimidazolium chloroaluminate, [BMIm]+Al2Cl7-, was used as a solvent as well as a Lewis acid catalyst in Fries rearrangement reactions of phenyl benzoates. The rate of consumption of phenyl benzoate obeyed first-order kinetics. Good yields and high selectivity are the features observed in this unconventional but interesting aprotic solvent.

Quaternary pyridinium ketoximes - New efficient micellar hydrolytic catalysts

Cibulka, Radek,Hampl, Frantisek,Kotoucova, Hana,Mazac, Jiri,Liska, Frantisek

, p. 227 - 242 (2000)

A series of quaternized alkyl pyridyl ketoximes was synthesized and tested as micellar hydrolytic catalysts. 2-And 4-|1-(hydroxyimino)tridecyl|-1-methylpyridinium bromides were surprisingly efficient, most probably due to the location of their nucleophili

Novel highly oxygenated and B-ring-seco-ent-diterpene glucosides from the seeds of Prinsepia utilis

Zhang, Qiao,Liu, Hong-Xin,Tan, Hai-Bo,Qiu, Sheng-Xiang

, p. 9415 - 9419 (2015)

Two novel highly oxygenated and one rare B-ring cleave ent-kaurane diterpene glucosides, named prinsoside A (1), B (2) and C (3), respectively, were isolated from an ethanolic extract of the seeds of Prinsepia utilis. To our knowledge, prinsoside B (2) was the most highly oxygenated ent-kaurane diterpene glucoside discovered in nature. Their structures were elucidated by various spectroscopic methods including 1D, 2D NMR and HR-ESI-MS analyses, with the absolute configurations clarified by CD measurements on their corresponding diterpenoid aglycones obtained by enzymatic hydrolysis with β-glucosidase. Compounds 1-3 exhibited weak α-glucosidase inhibitory activities.

Nitration of aromatic compounds catalyzed by divanadium-substituted molybdophosphoric acid, H5[PMo10V2O 40]

Heravi, Majid M.,Bakhtiari, Khadijeh,Benmorad, Tina,Bamoharram, Fatemeh F.,Oskooie, Hossein A.,Tehrani, Maryam H.

, p. 449 - 452 (2007)

The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H5PMo 10V2O40, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions. Springer-Verlag 2007.

Colloidal associates in the p-octylphenol / NaOH / water system and their catalytic properties at the phosphorus acid decomposition

Bakeeva, Roza,Kosacheva, Elmira,Bilalov, Azat,Kudryavtseva, Lyudmila,Barabanov, William,Sopin, Vladimir

, p. 573 - 583 (2001)

Using the tensiometric, potentiometric and conductivity methods we studied the association processes in the p-Octylphenol-NaOH-water system. We have used the spectrophotometric method and investigated the kinetic of decomposition of phosphorus acid esters

Electrochemical synthesis of alkyl nitroaromatic compounds

Gallardo, Iluminada,Guirado, Gonzalo,Marquet, Jordi

, p. 631 - 633 (2003)

Alkyl nitroaromatic compounds were readily prepared via nucleophilic aromatic substitution for hydrogen or a heteroatom by electrochemical oxidation of the a-complex. Butyllithium and butylmagnesium chloride were used as nucleophiles, and several nitrocompounds were tested to explore the possibilities of the NASH and NASX reactions promoted electrochemically.

Efficient catalytic promiscuity in an enzyme superfamily: An arylsulfatase shows a rate acceleration of 1013 for phosphate monoester hydrolysis

Olguin, Luis F.,Askew, Sarah E.,O'Donoghue, AnnMarie C.,Hollfelder, Florian

, p. 16547 - 16555 (2008)

We report a second catalytic activity of Pseudomonas aeruginosa arylsulfatase (PAS). Besides hydrolyzing sulfate monoesters, this enzyme catalyzes the hydrolysis of phosphate monoesters with multiple turnovers (>90), a kcat value of 0.023 ssup

Mild conversion of electron deficient aryl fluorides to phenols using 2-(methylsulfonyl)ethanol

Rogers, John F.,Green, Daniel M.

, p. 3585 - 3587 (2002)

Useful yields are achieved in the synthesis of phenols from aryl fluorides via a mild one-pot procedure using commercially available 2-(methylsulfonyl)ethanol. Examples and representative yields are shown.

The transition state of the phosphoryl-transfer reaction catalyzed by the lambda Ser/Thr protein phosphatase

Hoff, Richard H.,Mertz, Pamela,Rusnak, Frank,Hengge, Alvan C.

, p. 6382 - 6390 (1999)

The catalytic reaction of the Mn2+ form of the native bacteriophage λ phosphatase and the H76N mutant was studied with the substrate p-nitrophenyl phosphate using heavy atom isotope effects and pH-dependent rate studies. The kinetic isotope eff

Ultrasonic and microwave-assisted synthesis of β-nitro styrenes and nitro phenols with tertiary butyl nitrite under acid-free conditions

Kumar, M. Satish,Rajanna,Reddy, K. Rajendar,Venkateswarlu,Venkanna

, p. 2672 - 2677 (2013)

Tertiary butyl nitrite (TBN) is an acid-free and safe nitrating agent that provides preferentially β-nitrostyrenes with cinnamic acids and corresponding nitro derivatives with phenols in good yields under classical conditions. However, ultrasonic and microwave-assisted reactions reduced the reaction times substantially and enhanced the yields from good to excellent. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.

Supramolecular catalytic systems based on bolaform pyrimidinic surfactants: the counterion effect

Zakharova, Lucia Ya.,Syakaev, Victor V.,Voronin, Mikhail A.,Semenov, Vyacheslav E.,Valeeva, Farida G.,Giniyatullin, Rashit Kh.,Latypov, Shamil K.,Reznik, Vladimir S.,Konovalov, Alexander I.

, p. 116 - 118 (2010)

The catalytic effect of new amphiphilic pyrimidinic compounds with two ammonium head groups and different kinds of counterions, inorganic bromide anions and hydrophobic tosylate anions, was studied and compared with that of conventional cetyltrimethylammo

A mechanistic study on the α-N-acetylgalactosaminidase from E. meningosepticum: A family 109 glycoside hydrolase

Chakladar, Saswati,Shamsi Kazem Abadi, Saeideh,Bennet, Andrew J.

, p. 1188 - 1192 (2014)

A recombinant glycoside hydrolase family 109 α-N- acetylgalactosaminidase from the pathogenic bacteria E. meningosepticum catalyses the hydrolysis of aryl 2-acetamido-2-deoxy-α-d- galactopyranosides. The sensitivities to leaving group abilities (βlg

Efficient hydrolytic cleavage of phosphodiester with a lanthanide-based metal-organic framework

Dong, Yunhui,Dou, Yong,Qin, Lan,Yang, Lu,Zhang, Daopeng,Zhou, Zhen

, (2021)

Hydrolysis of phosphate diesters has attracted substantial research efforts, not only in bio-organic chemistry, but also in inorganic chemistry. Herein, a lanthanide-based metal-organic framework was synthesized by incorporating a tetraphenylethylene moiety as the four-point connected node, Ce-TCPE (noted as 1). The structural analyses indicate that 1 exhibits 3D framework connected by the sharing carboxylate groups with two kinds of 1D rhombic channels when viewed along the c direction. Hydrolytic cleavage catalysis have been performed and showed that 1 could act as efficient heterogeneous catalyst for the hydrolytic cleavage of the phosphodiester BNPP (bis(p-nitrophenyl)phosphate) with the high activity and hydrolytic stability in a pseudo-first-order rate. DFT studies has also gain an insight analysis to elucidate the cleavage process.

The effect of solvent on the α-effect: C=O, P=O and SO2 centers

Um,Hong,Buncel

, p. 27 - 28 (2001)

The α-effect for the reaction of a sulfonyl ester exhibits a bell-shaped dependence of the α-effect on solvent composition as do the corresponding reactions with a carbonyl and a phosphinyl ester, and the magnitude of the α-effect is found to be dependent

New 2-hydroxyethyl substituted N-Heterocyclic carbene precursors: Synthesis, characterization, crystal structure and inhibitory properties against carbonic anhydrase and xanthine oxidase

Akta?, Ayd?n,Noma, Samir Abbas Ali,Celepci, Duygu Barut,Erdemir, Fato?,G?k, Yetkin,Ate?, Burhan

, p. 487 - 494 (2019)

Here, the synthesis, spectral and the structural studies of 2-hydroxyethyl substituted N-heterocyclic carbene (NHC) precursors and the enzyme inhibition activities of the NHC precursors were investigated against the cytosolic carbonic anhydrase I and II i

Effect of copper on the activation of the acid phosphatase from the green algae Pseudokirchneriella subcapitata

Jonsson, Claudio Martin,Aoyama, Hiroshi

, p. 93 - 98 (2010)

The presence of copper in water environment may have detrimental effects on aquatic organisms, including algae, where different enzymatic systems can be affected. Algae acid phosphatase plays important roles in metabolic processes such as decomposition of

Optimized preparation of CALB-CLEAs by response surface methodology: The necessity to employ a feeder to have an effective crosslinking

Cruz, Jenniffer,Barbosa, Oveimar,Rodrigues, Rafael C.,Fernandez-Lafuente, Roberto,Torres, Rodrigo,Ortiz, Claudia

, p. 7 - 14 (2012)

Lipase B from Candida antarctica (CALB) has been immobilized using the CLEA technique. Due to the low content of surface Lys on the enzyme and the purity of the commercial preparation, CALB crosslinking did not work properly, and it was always possible to

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Hodgson,Birtwell,Marsden

, p. 112 (1944)

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Versatile de novo enzyme activity in capsid proteins from an engineered M13 bacteriophage library

Casey, John P.,Barbero, Roberto J.,Heldman, Nimrod,Belcher, Angela M.

, p. 16508 - 16514 (2014)

Biocatalysis has grown rapidly in recent decades as a solution to the evolving demands of industrial chemical processes. Mounting environmental pressures and shifting supply chains underscore the need for novel chemical activities, while rapid biotechnological progress has greatly increased the utility of enzymatic methods. Enzymes, though capable of high catalytic efficiency and remarkable reaction selectivity, still suffer from relative instability, high costs of scaling, and functional inflexibility. Herein, we developed a biochemical platform for engineering de novo semisynthetic enzymes, functionally modular and widely stable, based on the M13 bacteriophage. The hydrolytic bacteriophage described in this paper catalyzes a range of carboxylic esters, is active from 25 to 80 °C, and demonstrates greater efficiency in DMSO than in water. The platform complements biocatalysts with characteristics of heterogeneous catalysis, yielding high-surface area, thermostable biochemical structures readily adaptable to reactions in myriad solvents. As the viral structure ensures semisynthetic enzymes remain linked to the genetic sequences responsible for catalysis, future work will tailor the biocatalysts to high-demand synthetic processes by evolving new activities, utilizing high-throughput screening technology and harnessing M13's multifunctionality.

Gas-phase reaction of phenol with NO3

Bolzacchini, Ezio,Bruschi, Maurizio,Hjorth, Jens,Meinardi, Simone,Orlandi, Marco,Rindone, Bruno,Rosenbohm, Elisa

, p. 1791 - 1797 (2001)

The fast gas-phase reaction of NO3 radicals with phenol was found to yield 2-nitrophenol as the only relevant nitration product. The yield of this productwas high and independent of the concentration of NO2 at the concentrations appl

Green synthesis of isoamyl acetate via silica immobilized novel thermophilic lipase from Bacillus aerius

Narwal, Sunil Kumar,Saun, Nitin Kumar,Dogra, Priyanka,Gupta, Reena

, p. 69 - 73 (2016)

Isoamyl acetate, a pear or banana flavor, is widely used in food, beverage, cosmetic, and pharmaceutical industries. In the present work, lipase from Bacillus aerius was immobilized on silica gel matrix in the presence of a cross-linking agent, glutaraldehyde, and its efficiency in synthesizing isoamyl acetate using esterification reaction was studied. The esterification of acetic acid and isoamyl alcohol by silica-bound lipase was studied as a function of time and temperatures. The incubation time of 10 h, temperature of 55°C, substrate molar ratio 1: 1, and the amount of lipase as 1% were found to be optimal for the esterification reaction. The bound lipase catalyzed the esterification of acetic acid by isoamyl alcohol with the yield of about 68% under the optimized reaction conditions. The product was identified as isoamyl acetate using gas-liquid chromatography, nuclear magnetic resonance, and Fourier transform IR spectroscopy analysis by the presence of an ester group at the wavenumber of 1720.5 cm-1.

Differential catalytic promiscuity of the alkaline phosphatase superfamily bimetallo core reveals mechanistic features underlying enzyme evolution

Sunden, Fanny,Alsadhan, Ishraq,Lyubimov, Artem,Doukov, Tzanko,Swan, Jeffrey,Herschlag, Daniel

, p. 20960 - 20974 (2017)

Members of enzyme superfamilies specialize in different reactions but often exhibit catalytic promiscuity for one another's reactions, consistent with catalytic promiscuity as an important driver in the evolution of new enzymes. Wanting to understand how

The regiochemistry of the NO3-promoted gas phase nitration of toluene and phenol with NO2

Bolzacchini, Ezio,Bruschi, Maurizio,Galliani, Guido,Hjorth, Jens,Orlandi, Marco,Rindone, Bruno

, p. 570 - 578 (2006)

Product studies, kinetic isotope effect measurements, linear free energy relationships and calculations have been used to study the NO 3-promoted nitration of toluene and phenol in presence of NO 2. The competition between of a rate-

Purification and Characterization of an Esterase Involved in Poly(vinyl alcohol) Degradation by Pseudomonas vesicularis PD

Sakai, Kiyofumi,Fukuba, Masayuki,Hasui, Yutaka,Moriyoshi, Kunihiko,Ohmoto, Takashi,Fujita, Tokio,Ohe, Tatsuhiko

, p. 2000 - 2007 (1998)

An esterase catalyzing the hydrolysis of acetyl ester moieties in poly(vinyl alcohol) was purified 400-fold to electrophoretic homogeneity from the cytoplasmic fraction of Pseudomonas vesicularis PD, which was capable of assimilating poly(vinyl alcohol) a

STUDIES ON THERMODYNAMICS FOR THE HYDROLYSIS. II. THE TEMPERATURE EFFECT ON THE STEREOSELECTIVE DEACYLATION OF AMINO ACID ESTERS IN BILAYER AND MICELLAR SYSTEMS.

Matsumoto,Ueoka

, p. 3370 - 3375 (1983)

Stereoselective deacylations of p-nitrophenyl N-acyl-D(or L)-phenylalaninates(D(or L)-S//n; n equals 2, 12, and 16) and N-benzyloxycarbonyl-D(L)-phenylalaninates(D(L)-ZS) by the bilayer and micellar catalytic systems of L-histidine derivatives (LauHis, My

Detoxification of organophosphates using imidazole-coated Ag, Au and AgAu nanoparticles

Silva, Valmir B.,Rodrigues, Thenner S.,Camargo, Pedro H.C.,Orth, Elisa S.

, p. 40711 - 40719 (2017)

Organophosphate (OP) detoxification is a worldwide problem due to the high stability of P-O bonds. Here, we designed several imidazole-coated nanocatalysts targeted towards the cleavage of OP and thus their detoxification. Specifically, Ag, Au and bimetallic AgAu nanoparticles (NPs) supported on SiO2 were functionalized with methimazole (MTZ), which comprises thiol and imidazole groups, foreseeing enabling freely available imidazole groups. Raman analyses indicate that MTZ interacts preferably via its sulfur atom over Au NPs and via the nitrogen of the imidazole ring over Ag NPs. The MTZ-derived nanocatalysts were effective towards OP cleavage. For instance, rate enhancements of 108 fold were obtained for the toxic pesticide Paraoxon, compared to the uncatalyzed reaction. Interestingly, Au-derived nanocatalysts were significantly more effective since the imidazole group is free to react with the OP, which is not possible when Ag-N interactions take place.

Enzyme-Catalyzed Synthesis of Esters in Water

Mestrom, Luuk,Claessen, Jord G. R.,Hanefeld, Ulf

, p. 2004 - 2010 (2019)

MsAcT catalyzes the esterification of primary alcohols in water. When utilizing acid and alcohol as starting materials low yields dictated by thermodynamics were observed. However, with activated esters such as ethyl acetate and vinyl acetate very high yields of the desired ester can be achieved in combination with the appropriate alcohol. This study investigated both the intrinsic kinetic properties of MsAcT for the hydrolysis and transesterification of esters in water as well as the thermodynamics of the reaction. In comparison to the chemical or enzymatic ester synthesis using either toxic reagent, and harsh organic solvents, the MsAcT-catalyzed synthesis of esters of primary alcohols can be achieved efficiently in water without neutralization steps.

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Tagaki et al.

, p. 2894,2895, 2898 (1969)

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Chemical Mechanism of the Phosphotriesterase from Sphingobium sp. Strain TCM1, an Enzyme Capable of Hydrolyzing Organophosphate Flame Retardants

Bigley, Andrew N.,Xiang, Dao Feng,Ren, Zhongjie,Xue, Haoran,Hull, Kenneth G.,Romo, Daniel,Raushel, Frank M.

, p. 2921 - 2924 (2016)

The mechanism of action of the manganese-dependent phosphotriesterase from Sphingobium sp. strain TCM1 that is capable of hydrolyzing organophosphate flame retardants was determined. The enzyme was shown to hydrolyze the RP-enantiomer of O-meth

Long chain β-aminoethanols as micellar catalysts for the hydrolysis of diphenyl-p-nitrophenyl phosphate. The observation of an unusual enhancement of catalysis in the presence of added polyols

Oumar-Mahamat,Slebocka-Tilk,Brown

, p. 1577 - 1588 (1999)

The hydrolysis of p-nitrophenyldiphenyl phosphate (PNPDPP, 7) catalyzed by N-dodecylaminoethanol (6a), N-tetradecylaminoethanol (6b), N-methyl-N-tetradecylaminoethanol (6c), and N-hexadecylaminoethanol (6d) was investigated at 25°C at various pH values in aqueous media containing additives. Added ethanol or dimethoxyethane produces very little activity of 6a, b, c toward 7. The highest activities of 6a, b were found at pH 8.0 and 8.5 in solvents containing 20% glycerol or ethylene glycol. Under no conditions was N-hexadecylaminoethanol (6d) found to be active. The kinetics of the reaction of 6b with 7 were also investigated in a medium containing various amounts of glycerol, polyethylene glycol 400 (PEG 400), and water at pH 7.6-8.5. The best catalytic system comprised 3 mM 6b in 20% aqueous ethylene glycol, pH 8.5, which accelerated the hydrolysis of 7 by ~1700-fold over the blank rate. Kinetic experiments conducted using [7]/[6b] = 1 and 2 demonstrate that 6b exhibits true turnover catalysis. A mechanism for the catalyzed reaction is proposed.

Protein tyrosine phosphatase 1B inhibitors isolated from Morus bombycis

Hoang, Duc Manh,Ngoc, Tran Minh,Dat, Nguyen Tien,Ha, Do Thi,Kim, Young Ho,Luong, Hoang Van,Ahn, Jong Seog,Bae, KiHwan

, p. 6759 - 6761 (2009)

Bioassay-guided fractionation of the chloroform-soluble fraction of Morus bombycis, using an in vitro PTP1B inhibitory assay led to the identification of three 2-arylbenzofurans, albafuran A (1), mulberrofuran W (2) and mulberrofuran D (6), along with thr

Sonolytic degradation of parathion and the formation of byproducts

Yao, Juan-Juan,Gao, Nai-Yun,Deng, Yang,Ma, Yan,Li, Hai-Jun,Xu, Bin,Li, Lei

, p. 802 - 809 (2010)

Ultrasonic degradation of parathion has been investigated in this study. At a neutral condition, 99.7% of 2.9 μM parathion could be decomposed within 30 min under 600 kHz ultrasonic irradiation at ultrasonic intensity of 0.69 W/cm2. The degrada

Properties of a newly identified esterase from bacillus sp. K91 and its novel function in diisobutyl phthalate degradation

Ding, Junmei,Wang, Chaofan,Xie, Zhenrong,Li, Junjun,Yang, Yunjuan,Mu, Yuelin,Tang, Xianghua,Xu, Bo,Zhou, Junpei,Huang, Zunxi

, (2015)

The widely used plasticizer phthalate esters (PAEs) have become a public concern because of their effects on environmental contamination and toxicity on mammals. However, the biodegradation of PAEs, especially diisobutyl phthalate (DiBP), remains poorly understood. In particular, genes involved in the hydrolysis of these compounds were not conclusively identified. In this study, the CarEW gene, which encodes an enzyme that is capable of hydrolyzing ρ-nitrophenyl esters of fatty acids, was cloned from a thermophilic bacterium Bacillus sp. K91 and heterologously expressed in Escherichia coli BL21 using the pEASY-E2 expression system. The enzyme showed a monomeric structure with a molecular mass of approximately 53.76 kDa and pI of 4.88. The enzyme exhibited maximal activity at pH 7.5 and 45°C, with ρ-NP butyrate as the best substrate. The enzyme was fairly stable within the pH range from 7.0 to 8.5. High-pressure liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS) were employed to detect the catabolic pathway of DiBP. Two intermediate products were identified, and a potential biodegradation pathway was proposed. Altogether, our findings present a novel DiBP degradation enzyme and indicate that the purified enzyme may be a promising candidate for DiBP detoxification and for environmental protection.

ACCELERATED DEACYLATION OF ACYLATED INTERMEDIATE BY HYDROXYL FUNCTIONALIZED SURFACTANT MICELLES

Ihara, Yasuji,Okamoto, Mari,Nango, Mamoru,Koga, Joichi

, p. 1227 - 1230 (1985)

The rate constants of both acylation and deacylation processes in the hydrolysis of p-nitrophenyl esters by dipeptide catalysts have been determined in the presence of hydroxyl functionalized surfactant micelles.The functional surfactants enhance the deac

Structural and catalytic performance of a polyoxometalate-based metal-organic framework having a lanthanide nanocage as a secondary building block

Dang, Dongbin,Bai, Yan,He, Cheng,Wang, Jian,Duan, Chunying,Niu, Jingyang

, p. 1280 - 1282 (2010)

A polyoxometalate-based lanthanide-organic framework was achieved using the {[Ho4(dpdo)8(H2O)16BW 12O40] (H2O)2}7+ nanocage as a secondary building block fo

Spray-Coating of Catalytically Active MOF–Polythiourea through Postsynthetic Polymerization

Cohen, Seth M.,Kalaj, Mark

, p. 13984 - 13989 (2020)

A UiO-66-NCS MOF was formed by postsynthetic modification of UiO-66-NH2. The UiO-66-NCS MOFs displays a circa 20-fold increase in activity against the chemical warfare agent simulant dimethyl-4-nitrophenyl phosphate (DMNP) compared to UiO-66-NH2, making it the most active MOF materials using a validated high-throughput screening. The ?NCS functional groups provide reactive handles for postsynthetic polymerization of the MOFs into functional materials. These MOFs can be tethered to amine-terminated polypropylene polymers (Jeffamines) through a facile room-temperature synthesis with no byproducts. The MOFs are then crosslinked into a MOF–polythiourea (MOF–PTU) composite material, maintaining the catalytic properties of the MOF and the flexibility of the polymer. This MOF–PTU hybrid material was spray-coated onto Nyco textile fibers, displaying excellent adhesion to the fiber surface. The spray-coated fibers were screened for the degradation of DMNP and showed durable catalytic reactivity.

Nanostructured manganese oxides as highly active catalysts for enhanced hydrolysis of bis(4-nitrophenyl)phosphate and catalytic decomposition of methanol

??astny, Martin,Issa, Gloria,Popelková, Daniela,Ederer, Jakub,Kormunda, Martin,K?í?enecká, Sylvie,Henych, Ji?í

, p. 1766 - 1779 (2021)

Manganese oxide-based (MnOx) catalysts have received increasing attention due to their low cost, low toxicity, and the ability to degrade organic molecules under mild conditions. In this work, several nanostructured MnOx-based cataly

General base catalysis of ester hydrolysis

Stefanidis, Dimitrios,Jencks, William P.

, p. 6045 - 6050 (1993)

The hydrolysis of alkyl formates with leaving groups in the range pKa = 12-16 is catalyzed by substituted acetate anions. There is an increase in the Br?nsted β value for general base catalysis with decreasing pKa of the leaving alcohol and a complementary increase in -β1g with decreasing pKa of the catalyzing base, both of which are consistent with a value of pxy = ?β/-pK1g = ?β1g/-?pKBH ? 0.11. This result supports a class n mechanism of general base catalysis, in which a proton is abstracted from the nucleophilic water molecule by the base catalyst in the transition state; it is not consistent with the kinetically equivalent class e mechanism of electrophilic catalysis by general acids of a reaction with hydroxide ion, by proton donation to the leaving alcohol. Solvent deuterium isotope effects in the range kH2O/kD2O = 3.6-5.3 for the buffer-independent reaction and 2.5-2.8 for catalysis by CHaCOO- support concerted proton transfer and O-C bond formation. The secondary isotope effect for catalysis of the hydrolysis of LCOOMe by acetate ion is kD/kH = 1.05. Both nucleophilic and general base mechanisms of catalysis by acetate anions are observed for the hydrolysis of substituted phenyl formates with leaving groups of pKa = 7.1-10.1. A small value of β = 0.12 for general base catalysis of the hydrolysis of phenyl formate and p-methylphenyl formate represents catalysis of the addition of water by hydrogen bonding of water to the base catalyst. On the other hand, a larger value of β = 0.35 and a decrease in kH2O/kD2O to 1.2 were observed for general base catalysis of the hydrolysis of p-nitrophenyl formate. It is suggested that the increase in β with decreasing pK1g (an apparent "anti-Hammond effect") may be accounted for by a change in mechanism, from catalysis of a stepwise reaction of phenyl and p-methylphenyl formates to concerted general base catalysis of formyl transfer to water for the reaction of p-nitrophenyl formate.

Kinetic and mechanistic investigation of a hydrolytic catalytic antibody having remarkable substrate specificity: Substituent effects on catalysis

Wada, Yumiko,Yamamoto, Masayoshi,Sudo, Yukio,Ono, Mitsunori

, p. 477 - 483 (1999)

Monoclonal antibodies were raised against p-nitrophenyl phosphonate to elicit catalytic antibodies capable of hydrolyzing p-nitrophenyl carbonates. Of 34 clones selected, three clones catalyzed the hydrolysis of methyl p- nitrophenyl carbonate. Interestin

Nitric oxide-triggered heme-mediated hydrolysis: A possible model for biological reactions of NO

Traylor, Teddy G.,Duprat, Arthur F.,Sharma, Vijay S.

, p. 810 - 811 (1993)

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A mild palladium(II) catalyzed desilylation of phenolic t-butyldimethylsilyl ethers

Wilson, Noel S.,Keay, Brian A.

, p. 153 - 156 (1996)

A variety of phenolic t-butyldimethylsilyl ethers are easily removed in good to excellent yields by treatment with 5 mol% PdCl2(CH3CN)2 in refluxing acetone containing 5 equivalents of water.

Synthesis of benzyl β-d-galactopyranoside by transgalactosylation using a β-galactosidase produced by the over expression of the Kluyveromyces lactis LAC4 gene in Arxula adeninivorans

Rauter, Marion,Schwarz, Maria,Becker, Karin,Baronian, Keith,Bode, Ruediger,Kunze, Gotthard,Vorbrodt, H.-Matthias

, p. 319 - 327 (2013)

The LAC4 gene of Kluyveromyces lactis encoding for β-galactosidase was overexpressed in the yeast Arxula adeninivorans to produce the enzyme, which can be used for the synthesis of β-d-galactosides. These compounds play a major role as precursors for the

Purification and Some Properties of a β-Glucosidase from Trichoderma harzianum Type C-4

Yun, Soo-In,Jeong, Choon-Soo,Chung, Dae-Kyun,Choi, Hye-Seon

, p. 2028 - 2032 (2001)

Type C-4 strain of Trichoderma harzianum was isolated as a microorganism with high cellulolytic activity. β-Glucosidase is involved in the last step of cellulose saccharification by degrading cellobiose to glucose, and plays an important role in the cellu

A calixresorcinarene provides the framework for an artificial esterase

Pirrincioglu, Necmettin,Zaman, Flora,Williams, Andrew

, p. 2561 - 2562 (1996)

An octa(dimethylaminopropyl)calixresorcin[4]arene (1c) is a primitive artificial esterase for 4-nitrophenyl esters.

Cu(II)-Mediated decomposition of phosphorothionate P=S pesticides. Billion-fold acceleration of the methanolysis of fenitrothion promoted by a simple Cu(II)-ligand system

Neverov, Alexei A.,Brown, R. Stan

, p. 2245 - 2248 (2004)

The kinetics of methanolysis of the title compound (3) were studied in the presence of Cu2+, introduced as Cu(OTf)2, in the presence of 0.5-1.0 eq. of methoxide and in the presence of 1.0 eq. of a ligand such as bipyridyl (5), phenanthroline (6) or 1,5,9-triazacyclododecane (4). In all cases the active species involve Cu2+(-OCH3). In the case of added strongbinding ligands 5 or 6, a plot of the observed rate constant for methanolysis of 3 vs. [Cu2+]total gives a curved line modelled by a process having a [Cu2+]1/2 dependence consistent with an active monomeric species in equilibrium with an inactive dirtier i.e. {LCu2+(-OCH3)} 2→2LCu2+(-OCH3). In the case of the added strong binding ligand 4, the plot of the observed rate constant for methanolysis of 3 vs. [Cu2+]total gives a straight line consistent with the catalytically active species being 4Cu 2+(OCH3) which shows no propensity to form inactive dimers. Turnover experiments where the [3] > [Cu2+] total indicate that the systems are truly catalytic. In the optimum case a catalytic system comprising 1 mM of the complex 4Cu2+( -OCH3) catalyzes the methanolysis of 3 with a t 1/2 of ~58 s accounting for a 1.7 × 109-fold acceleration relative to the background reaction at near neutral sspH (8.75).

A comparative study on NHC-functionalized ternary Se/Te-Fe-Cu compounds: Synthesis, catalysis, and the effect of chalcogens

Shieh, Minghuey,Liu, Yu-Hsin,Wang, Chih-Chin,Jian, Si-Huan,Lin, Chien-Nan,Chen, Yen-Ming,Huang, Chung-Yi

, p. 11832 - 11843 (2019)

A novel family of N-heterocyclic carbene (NHC)-incorporated Se-Fe-Cu compounds, bis-1,3-dimethylimidazol-2-ylidene (bis-Me2-imy)-containing compound [(μ4-Se)Fe3(CO)9{Cu(Me2-imy)}2] (2), bis-N-methyl- or bis-N-isopropyl-substituted benzimidazol-2-ylidene (bis-Me2-bimy or bis-iPr2-bimy)-incorporated compounds [(μ4-Se)Fe3(CO)9{Cu(Me2-bimy)}2] (3) or [(μ4-Se)Fe3(CO)9{Cu(iPr2-bimy)}2] (4), and a bis-1,3-dimethyl-4,5-dichloroimidazol-2-ylidene (bis-Me2-Cl2-imy)-containing compound [(μ3-Se)Fe3(CO)9{Cu(Me2-Cl2-imy)}2] (5), were synthesized in moderate yields in facile one-pot reactions of the ternary pre-designed compound [(μ3-Se)Fe3(CO)9{Cu(MeCN)}2] (1) with the corresponding imidazolium salts and KOtBu in THF in an ice-water bath. Single-crystal X-ray analyses revealed that the Me2-imy compound 2 or the Me2-bimy compound 3 each exhibited a trigonal bipyramidal SeFe3(CO)9Cu geometry with an Fe2Cu plane further capped by a Cu(Me2-imy) or Cu(Me2-bimy) fragment, respectively, with one long Cu-Cu covalent bond. In addition, compound 4 also comprised a trigonal bipyramidal SeFe3(CO)9Cu core structure, but the second Cu(iPr2-bimy) group bridged the equatorial Fe-Fe edge with two unbonded Cu atoms, due to the presence of a sterically bulky iPr2-bimy fragment. On the other hand, the strong electron-withdrawing chloro-containing NHC compound 5 showed a comparatively open tetrahedral SeFe3(CO)9 metal core, where two Fe-Fe edges each were further bridged by a Cu(Me2-Cl2-imy) fragment. Due to the nonclassical C-H?O(carbonyl) hydrogen bonds between the CO groups of the SeFe3(CO)9Cu2 core and CH moieties of the neighboring NHC ligands, both compounds 2 and 3 comprised a one-dimensional network, while compounds 4 and 5 each were made up of a two-dimensional framework in the solid state, which efficiently enhanced the stability of these Se-Fe-Cu NHC compounds. Importantly, all of these synthesized Se-Fe-Cu NHC compounds 2-5 had pronounced catalytic activities for the homocoupling of arylboronic acids with high catalytic yields. Finally, these Se-containing Fe-Cu NHC compounds further represented excellent models for studying chalcogen effects in comparison to their Te analogs, as demonstrated by their catalytic performances and electrochemical behaviors, and by DFT calculations.

Phenol photonitration upon UV irradiation of nitrite in aqueous solution I: Effects of oxygen and 2-propanol

Vione, Davide,Maurino, Valter,Minero, Claudio,Pelizzetti, Ezio

, p. 893 - 902 (2001)

Nitrophenols are formed in aqueous solution upon UV irradiation of phenol and nitrite. The formation of nitrophenols is enhanced by dissolved oxygen and inhibited by the addition of 2-propanol. The mechanism of phenol photonitration involves both NO2 (or N2O4), reacting with phenol, and 4-nitrosophenol, which is oxidised to 4-nitrophenol. A reaction scheme is proposed based on experimental results.

Kinetic study of alkaline hydrolysis of substituted phenyl tosylates. XXII. Variation of ortho substituent effect with solvent

Nummert, Vilve,Piirsalu, Mare,Lepp, Marika,Maeemets, Vahur,Koppel, Ilmar

, p. 198 - 222 (2005)

The second-order rate constants k (dm3 mol-1 s -1) for the alkaline hydrolysis of meta-, para-, and ortho-substituted phenyl tosylates 4-CH3C6H 4SO2OC6H4-X in aqueous 0.5 M Bu 4NBr have been measured spectrophotometrically in a wide temperature range. The log k values for ortho-substituted derivatives at various temperatures together with meta- and para-substituted derivatives were analyzed using the modified Fujita-Nishioka equation log km,p,ortho = c 0 + c1(m,p,ortho)σ° + c 2(ortho)σ1 + c3(1/T) + c 4(m,p,ortho)(1/T)σ° + c5(ortho)(1/T) σI. In order to study the dependence of substituent effects, especially ortho inductive and resonance terms on different solvent parameters, the following equation was used: Δlog km,p,ortho = c 0 + c1(m,p,ortho)σ° + c 2(ortho)σI + c3ΔE + c 4ΔY + c5ΔP + c 6(m,p,ortho)ΔEσ° + + c 7(m,p,ortho)ΔYσ° + c 8(m,p,ortho)ΔPσ° + c 9(ortho)ΔEσI + c 10(ortho)ΔYσI + c 11(ortho)ΔPσI. Δlog k = log k X - log kH, σ° and σI, are the Taft polar and inductive substituent constants, E, Y and P, are the solvent electrophilicity, polarity and polarizability parameters, respectively. In data treatment ΔE = ES - EH2O, ΔY = YS - YH2O, ΔP = PS - PH2O were used. The solvent electrophilicity was found to be the main factor responsible for changes in the ortho, para, and meta polar substituent effects with medium. The variation of the ortho inductive term with the solvent electrophilicity E S was found to be twice smaller than that for para substituents, while the ortho resonance term appeared to vary with solvent nearly similarly to that for para substituents. The ortho effect caused by the supplementary inductive effect from ortho position was found to disappear in a solvent whose electrophilic solvating power is comparable to pure DMSO (E ≈ 4).

Immobilization of isolated lipase from moldy copra (aspergillus oryzae)

Dali, Seniwati,Patong, A B D. Rauf,Jalaluddin, M. Noor,Pirman,Hamzah, Baharuddin

, p. 896 - 902 (2011)

Enzyme immobilization is a recovery technique that has been studied in several years, using support as a media to help enzyme dissolutions to the reaction substrate. Immobilization method used in this study was adsorption method, using specific lipase fro

A novel and simple solvent free method for nucleophilic aromatic substitution of inactive aryl halides

Hashemi, Mohammed M.,Akhbari, Maryam

, p. 2783 - 2787 (2004)

A simple, high yield, and short time method for nucleophilic displacement reaction of inactive aryl halides is reported. The reaction is performed in microwave oven under thermal condition with montmorillonite supported AgNO 3.

Effect of low organic solvents concentration on the stability and catalytic activity of HSL-like carboxylesterases: Analysis from psychrophiles to (hyper)thermophiles

Mandrich, Luigi,De Santi, Concetta,De Pascale, Donatella,Manco, Giuseppe

, p. 46 - 52 (2012)

A comparative study aiming at analysing the catalytic activity and stability of four related enzymes belonging to the HSL family in the presence of several water-miscible organic solvents was performed. The studied enzymes were four carboxylesterases: Psy

Identification of rice β-glucosidase with high hydrolytic activity towards salicylic acid β-d-glucoside

Himeno, Nami,Saburi, Wataru,Wakuta, Shinji,Takeda, Ryosuke,Matsuura, Hideyuki,Nabeta, Kensuke,Sansenya, Sompong,Ketudat Cairns, James R.,Mori, Haruhide,Imai, Ryozo,Matsui, Hirokazu

, p. 934 - 939 (2013)

β-Glucosidases (EC 3.2.1.21) split β-glucosidic linkages at the non-reducing end of glucosides and oligosaccharides to release β-D-glucose. One of the important functions of plant β-glucosidase is deglucosylation of inactive glucosides of phytohormones to regulate levels of active hormones. Tuberonic acid is a jasmonaterelated compound that shows tuber-inducing activity in the potato. We have identified two enzymes, OsTAGG1 and OsTAGG2, that have hydrolytic activity towards tuberonic acid β-D-glucoside in rice (Oryza sativa L.). The expression of OsTAGG2 is upregulated by wounding and by methyl jasmonate, suggesting that this isozyme is involved in responses to biotic stresses and wounding, but the physiological substrate of OsTAGG2 remains ambiguous. In this study, we produced recombinant OsTAGG2 in Pichia pastoris (rOsTAGG2P), and investigated its substrate specificity in detail. From 1L of culture medium, 2.1mg of purified recombinant enzyme was obtained by ammonium sulfate precipitation and Ni-chelating column chromatography. The specific activity of rOsTAGG2P (182 U/mg) was close to that of the native enzyme (171 U/mg), unlike recombinant OsTAGG2 produced in Escherichia coli, which had approximately 3-fold lower specific activity than the native enzyme. The optimum pH and temperature for rOsTAGG2P were pH 3.4 and 60 βC. After pH and heat treatments, the enzyme retained its original activity in a pH range of 3.4-9.8 and below 55 βC. Native OsTAGG2 and rOsTAGG2P showed 4.5-4.7-fold higher activities towards salicylic acid β-D-glucoside, an inactive storageform of salicylic acid, than towards tuberonic acid β-Dglucoside (TAG), although OsTAGG2 was originally isolated from rice based on TAG-hydrolytic activity.

Eliminating positively charged lysine ε-NH3+ groups on the surface of carbonic anhydrase has no significant influence on its folding from sodium dodecyl sulfate

Gudiksen, Katherine L.,Gitlin, Irina,Yang, Jerry,Urbach, Adam R.,Moustakas, Demetri T.,Whitesides, George M.

, p. 4707 - 4714 (2005)

This study compares the folding of two polypeptides-bovine carbonic anhydrase (BCA) and peracetylated BCA (BCA-Ac18)-having the same sequence of amino acids but differing by 18 formal units of charge, from a solution containing denaturing conce

Structure-reactivity Relationships as Probes to Acetylcholinesterase Inhibition Mechanisms by Aryl Carbamates. II. Hammett-Taft Cross-interaction Correlations

Lin, Gialih

, p. 423 - 429 (2014)

Substituted phenyl-N-butyl carbamates (1) and p-nitrophenyl-N-substituted carbamates (2) are characterized as "pseudo-pseudo-substrate" inhibitors of acetylcholinesterase. Since the inhibitors protonate in pH 7.0 buffer solution, the virtual inhibition co

SIGMA COMPLEXES IN THE PYRIMIDINE SERIES. 8. RECYCLIZATION OF ACETONYL ANIONIC ?-COMPLEXES OF 5-NITROPYRIMIDINE AND ITS DERIVATIVES

Remennikov, G. Ya.,Kurilenko, L.K.,Boldyrev, I. V.,Cherkasov, V. M.

, p. 1336 - 1338 (1987)

The transformation of the pyrimidine ring in the reaction of acetonyl anionic ?-complexes of 5-nitropyrimidine and its derivatives with strong base was studied.It is shown that when there is a geminal node at the 4 position, recyclization of the pyrimidin

Contribution of the two domains of E. coli 5′-nucleotidase to substrate specificity and catalysis

Krug, Ulrike,Patzschke, Rica,Zebisch, Matthias,Balbach, Jochen,Str?ter, Norbert

, p. 460 - 466 (2013)

Escherichia coli 5′-nucleotidase, a two-domain enzyme, dephosphorylates various nucleotides with comparable efficiency. We have expressed the two domains individually in E. coli and show by liquid state NMR that they are properly folded. Kinetic characterization reveals that the C-terminal domain, which contains the substrate-binding pocket, is completely inactive while the N-terminal domain with the two-metal-ion-center and the core catalytic residues exhibits significant activity, especially towards substrates with activated phosphate bonds (ATP, ADP, p-nitrophenyl phosphate). In contrast, residues of the C-terminal domain are required for efficient hydrolysis of AMP.

A synthetic p-nitrophenyl esterase with remarkable substrate selectivity

Fife, Wilmer K.,Rubinsztajn, Slawomir,Zeldin, Martel

, p. 8535 - 8537 (1991)

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Bolaform and Classical Cationic Metallomicelles as Catalysts of the Cleavage of p-Nitrophenyl Picolinate

Fornasier, Roberto,Scrimin, Paolo,Tecilla, Paolo,Tonellato, Umberto

, p. 224 - 229 (1989)

Bolaform micelles made of ligand surfactants 6-(((12-(trimethylammonio)-n-dodecanoyl)amino)methyl)-2-(hydroxymethyl)pyridine bromide (1) or 6-(((10-(trimethylammonio)-n-decyl)thio)methyl)-2-(hydroxymethyl)pyridine bromide (3) in the presence of Cu(II) or Zn(II) ions are good catalysts of the hydrolysis of p-nitrophenyl picolinate (PNPP).In the presence of 4.6x1E-4 M Cu(II) at pH=6.25 and 25 deg C, 2x1E-3 M 1 and 3 cleave PNPP with kinetic advantages of 7.6x1E5 and 1.6x1E6, respectively, over the uncatalyzed hydrolysis of the substrate.Classical micelles made of surfactant 6-(((2-(n-hexadecyldimethylammonio)ethyl)thio)methyl)-2-(hydroxymethyl)pyridine bromide (5) are less efficient ligands for Cu(II) or Zn(II) ions and poorer catalysts of the cleavage of PNPP than 1 or 3 due to the proximity and hence to the electrostatic repulsion between the ammonium group and the metal ion coordination site.The critical feature of the catalytic process is, quite likely, the formation of a ternary complex (8) involving ligand, metal ion, and substrate.The (deprotonated) hydroxyl bound to the pyridine moiety of the catalyst in the ternary complex acts as a nucleophile leading to a transacylation intermediate that undergoes a rapid, metal ion assisted hydrolysis "turning over" the catalyst.In all cases the micellar systems are better catalysts than the corresponding neutral nonmicellar models.This indicates that concentration effects coupled with a more facile acid dissociation of the hydroxyl and, possibly, with an enhanced electrophilicity of the metal ion in the aggregates largely offset the adverse electrostatic interactions between the metal ions and the positively charged micellar surface.

Synthesis and evaluation of general mechanism-based inhibitors of sulfatases based on (difluoro)methyl phenyl sulfate and cyclic phenyl sulfamate motifs

Hanson, Sarah R.,Whalen, Lisa J.,Wong, Chi-Huey

, p. 8386 - 8395 (2006)

Several model mechanism-based inhibitors (MbIs) were designed and evaluated for their ability to inhibit sulfatases. The MbI motifs were based on simple aromatic sulfates, which are known to be commonly accepted substrates across this highly conserved enzyme class, so that they might be generally useful for sulfatase labeling studies. (Difluoro)methyl phenol sulfate analogs, constructed to release a reactive quinone methide trap, were not capable of irreversibly inactivating the sulfatase active site. On the other hand, the cyclic sulfamates (CySAs) demonstrated inhibition profiles consistent with an active site-directed mode of action. These molecules represent a novel scaffold for labeling sulfatases and for probing their catalytic mechanism.

Amino-acetone-bridged cyclodextrins - Artificial alcohol oxidases

Marinescu, Lavinia G.,Doyagueez, Elisa G.,Petrillo, Marta,Fernandez-Mayoralas, Alfonso,Bols, Mikael

, p. 157 - 167 (2010)

A new series of α-and β-cyclodextrin derivatives containing a substituted amino-acetone bridge attached to the 6A and 6D positions of the cyclodextrin are reported. The synthesis starts from the known α-or β-cyclodextrin A,D-diols, which were either oxidized to α-or β-cyclodextrin A,D-dicarbaldehydes and then coupled with 1,3-diamino-2-propanol by a reductive amination reaction and further modified to give the final 6A,6D-diamino-6A,6 D-dideoxy-N,N'-(2-oxopropa-1,3-dienyl)-N,N'-acetyl-α-or-β- cyclodextrin or the cyclodextrindiol was substituted with azide then reduced and after a few alkylation steps the final 6A,6D-dideoxy-N, N'-(2-oxopropa-1,3-dienyl)-6A,6D-(N,N,N'N'- tetramethyldiammonio)-α-cyclodextrin dibromide was obtained. The new compounds display very good enzymatic catalytic properties in the oxidation of benzyl alcohols with a rate increase of up to 18500 but only appreciable catalysis for aniline oxidations. Thus, unlike previously studied cyclodextrin ketones, these new amino-acetone-bridged cyclodextrins have high substrate selectivity and also exhibit stereoselectivity in the oxidation of different enantiomers.

Formation of OH Radicals from Radical Cations of Some Substituted Benzenes in Aqueous Solutions at 80 degC and at Room Temperature. Effect of Oxygen

Eberhardt, Manfred K.,Fuentes-Aponte, Anselmo

, p. 3444 - 3448 (1983)

The reactions of a number of simple substituted-benzene radical cations with water at 80 degC and at room temperature have been investigated.The radical cations were produced by thermal decomposition of Na2S2O8.We searched for the formation of OH radicals

Influence of co-ligands in synthesis, photoluminescence behavior and catalytic activities of zinc complexes of 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol

Kundu, Priyanka,Chakraborty, Prateeti,Adhikary, Jaydeep,Chattopadhyay, Tanmay,Fischer, Roland C.,Mautner, Franz A.,Das, Debasis

, p. 320 - 328 (2015)

Four new zinc(II) complexes of a tridentate Schiff base ligand 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol (HL), namely [Zn2L2Cl2] (1); [Zn2L2Br2] (2); [ZnL(SCN)(MeOH)] (3) and [Zn

Hydrolysis of toxic natural glucosides catalyzed by cyclodextrin dicyanohydrins

Bjerre, Jeannette,Nielsen, Erik Holm,Bols, Mikael

, p. 745 - 752 (2008)

The hydrolysis of toxic 7-hydroxycoumarin glucosides and other aryl and alkyl glucosides, catalyzed by modified α- and β-cyclodextrin dicyanohydrins, was investigated using different UV, redox, or HPAEC detection assays. The catalyzed reactions all followed Michaelis-Menten kinetics, and an impressive rate increase of up to 7569 (kcat/kuncat) was found for the hydroxycoumarin glucoside substrate 4-MUGP. Good and moderate degrees of catalysis (kcat/kuncat) of up to 1259 were found for the natural glucosides phloridzin and skimmin. By using a newly developed catechol detection UV-assay, a weak degree of catalysis was also found for the toxic hydroxycoumarin esculin. A novel synthesized diaminomethyl β-cyclodextrin showed a weak catalysis of p-nitrophenyl β-D-glucopyranoside hydrolysis. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Novel chains constructed from heterotrinuclear units and 1,2-bis(4-pyridyl)ethane formulated as [M2M′(O2CPh)6](bpa) (M = Co, Zn, M′ = Co, Cd): Their catalytic activity

Lee, Young Min,Song, Young Joo,Poong, Jung In,Kim, Soo Hyun,Koo, Hyo Geun,Lee, Jung Ah,Kim, Cheal,Kim, Sung-Jin,Kim, Youngmee

, p. 101 - 104 (2010)

Three novel heterometallic complexes containing two bridging ligands bpa and benzoate, formulated as [M2M′(O2CC6H5]n(bpa)n (bpa = 1,2-bis(4-pyridyl)ethane, M2M′ = Zn2Co (1), Zn2Cd (2), and Co2Cd (3)), have been synthesized. All three compounds show one-dimensional structures containing linear heteronuclear coordination units linked by bridging bpa ligands. Reactivity study of the compounds 1-3 for the transesterification of a variety of esters has shown that they are very efficient and 2 is the best among them.

Destruction of chemical warfare agent simulants by air and moisture stable metal NHC complexes

Weetman, Catherine,Notman, Stuart,Arnold, Polly L.

, p. 2568 - 2574 (2018)

The cooperative effect of both NHC and metal centre has been found to destroy chemical warfare agent (CWA) simulants. Choice of both the metal and NHC is key to these transformations as simple, monodentate N-heterocyclic carbenes in combination with silver or vanadium can promote stoichiometric destruction, whilst bidentate, aryloxide-tethered NHC complexes of silver and alkali metals promote breakdown under mild heating. Iron-NHC complexes generated in situ are competent catalysts for the destruction of each of the three targetted CWA simulants.

Reduction and Substitution in the Reaction of 4-Chloronitrobenzene with Alkoxides

Bassani, Alberto,Prato, Maurizio,Rampazzo, Paolo,Quintily, Ugo,Scorrano, Gianfranco

, p. 2263 - 2264 (1980)

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Reaction of 1,2-difunctionalized ethanes with aryl iodides in copper-catalyzed cross-coupling: Application to synthesis of phenols

Kim, Jihye,Battsengel, Oyunsaikhan,Liu, Yajun,Chae, Junghyun

, p. 2833 - 2840 (2015)

A series of 1,2-difunctionalized ethanes, such as ethylene glycol, 2-aminoethanol, 1,2-diaminoethane, 2-dimethylaminoethanol N',N'-dimethylethane-1,2-diamine, were investigated to test the reactivity with aryl iodides in the presence of copper catalysts. Under the reaction conditions, they produce the various Cheteroatom cross-coupled products. Interestingly, ethylene glycol and 2-dimethylaminoethanol afforded mainly the phenolic compounds while the others produced different cross-coupled products. Although ethylene glycol and 2-dimethylaminoethanol resulted in the same product, their behaviors in the reaction were quite different: ethylene glycol appears to mostly act as the ligand and 2-dimethylaminoethanol appears to serve as both the ligand and reactant. This finding led to a copper-catalyzed synthesis of phenols using either ethylene glycol or 2-dimethylaminoethanol, which can be applied to a variety of aryl iodides, providing an alternative synthetic route to phenols.

Hydrolytic Metalloenzyme Models. Micellar Effects on the Activation of the Hydroxyl Groups of N-Alkyl-2-(hydroxymethyl)-imidazole Ligands by Cu2+ in the Transacylation of p-Nitrophenol Picolinate

Tagaki, Waichiro,Ogino, Kenji,Tanaka, Osamu,Machiya, Koji,Kashihara, Nobuyuki,Yoshida, Toshiharu

, p. 74 - 80 (1991)

The activation of the hydroxyl groups of two N-methyl/dodecyl-2-(hydroxymethyl)imidazole ligands by complexation with Cu2+ was investigated kinetically by observing the rates of the release of p-nitrophenol in the transacylation of p-nitropheny

Effects of truncation at the non-homologous region of a family 3 β-glucosidase from Agrobacterium tumefaciens

Ying, Li,Kitaoka, Motomitsu,Hayashi, Kiyoshi

, p. 1113 - 1118 (2004)

The function of the non-homologous region of a family 3 β-glucosidase from Agrobacterium tumefaciens (Cbg1) was studied by analyzing the properties of mutant enzymes that have internal truncated amino acid sequences in the region. Five truncated mutants n

Silica chloride: An efficient promoter for oxidation of arylboronic acids to phenols

Wagh, Ravindra B.,Nagarkar, Jayashree M.

, p. 3323 - 3326 (2017)

This work reports simple, highly efficient protocol for the oxidation of arylboronic acids. Various arylboronic acids were selectively and completely converted into their corresponding oxidized phenols using H2O2 as an oxidant in presence of catalytic amount of silica chloride. The results show that silica chloride is a suitable and efficient promoter for the oxidation of arylboronic acids. Heterogeneous catalyst, mild reaction conditions, easy availability of the reagent, easy work-up, excellent yield of corresponding phenols, short reaction time and broad substrate scope makes this protocol attractive and a practical alternative to the existing methods.

On/off regulation of catalysis by allosteric control of metal complex nuclearity

Kovbasyuk, Larisa,Pritzkow, Hans,Kraemer, Roland,Fritsky, Igor O.

, p. 880 - 881 (2004)

The nature of the allosteric metal ion M (Pd2+ or Pt 2+) in complexes ML of a polytopic ligand controls uptake of additional Cu2+ ions; while [Cu2Pd(L-4H)]2+ is a highly active catalyst for phosphodie

Aluminum nitrate and silica sulfuric acid as efficient nitrating media for the mononitration of phenols under mild and heterogeneous conditions

Ghorbani-Choghamarani, Arash,Goudarziafshar, Hamid,Nikoorazm, Mohsen,Yousefi, Somaieh

, p. 1144 - 1147 (2009)

A variety of phenol derivatives were successfully nitrated via combination of Al(NO3)3-9H2O and silica sulfuric acid in the presence of wet SiO2 (50% w/w) in dichloromethane at room temperature with moderate-to-good yields.

Magnetic nanoparticles coated with immobilized alkaline phosphatase for enzymolysis and enzyme inhibition assays

Wang, Siming,Su, Ping,Huang, Jun,Wu, Jingwei,Yang, Yi

, p. 1749 - 1754 (2013)

Magnetic nanoparticles are potentially useful as supports for biomacromolecules because of their biocompatibility, low toxicity and easy separation. In this study, alkaline phosphatase (ALP) was used as a model enzyme, and a new type of immobilized ALP wa

Phosphorylation of alkylated poly(ethyleneimine) in chloroform in the presence of cetyltrimethylammonium bromide and calix[4]resorcinarene

Gainanova,Zhil'tsova,Kudryavtseva,Lukashenko,Timosheva,Konovalov

, p. 953 - 958 (2007)

The phosphorylation of alkylated poly(ethyleneimine) with 4-nitrophenyl bis(chloromethyl)phosphinate in chloroform in the presence of cetyltrimethylammonium bromide (CTAB), calix[4]resorcinarene (CR), or their mixture was studied by UV spectrophotometry.

Purification and Properties of Three β-N-Acetylglucosaminidases from Lactobacillus casei ATCC 27092

Senba, Mio,Kashige, Nobuhiro,Miake, Fumio,Watanabe, Kenji

, p. 404 - 406 (1998)

Three β-N-acetylglucosaminidases, GlcNAcase A, B, and C, were purified from the culture fluid of Lactobacillus casei ATCC 27092, and the molecular weights of these enzymes were estimated to be 54,000, 51,000, and 44,000, respectively, by SDS-PAGE.The prod

1,3-Dihalo-5,5-dimethylhydantoin or citric acid/NaNO2 as a heterogeneous system for the selective mononitration of phenols under mild conditions

Zolfigol, Mohammad A.,Ghaemi, Ezat,Madrakian, Elaheh,Choghamarani, Arash G.

, p. 41 - 42 (2006)

Direct nitration of phenols was performed using 1,3-dichloro-5,5- dimethylhydantoin, 1,3-dibromo-5,5-dimethylhydantoin or citric acid/NaNO 2 in the presence of wet SiO2 at room temperature.

Trinuclear Mn2+/Zn2+based microporous coordination polymers as efficient catalysts foripso-hydroxylation of boronic acids

Bora, Sanchay J.,Dutta, Anurag,Goswami, Shyam,Guha, Ankur K.,Paul, Rima,Thakur, Ashim J.

, p. 5454 - 5462 (2020)

Two microporous coordination polymers based on hourglass trinuclear building units, [Mn3(bpdc)3(bpy)]·2DMF and [Zn3(bpdc)3(bpy)]·2DMF·4H2O (bpdc = 4,4′-biphenyl dicarboxylic acid, bpy = 4,4′-bipyridine), have been synthesized under solvothermal conditions employing DMF as the solvent. Each structure consists of two crystallographically distinct M2+(M1 and M2) centers that are connectedviacarboxylate bridges from six bpdc ligands, generating a trinuclear metal cluster, [M3(bpdc)3(bpy)]. Cluster representation of the structure resulted in an interpenetrated net of rarehextopological type. Catalytic activities of the CPs have been assessed for the oxidative hydroxylation of phenylboronic acids (PBAs) using aqueous hydrogen peroxide (H2O2). Various substituted aryl/hetero-arylboronic acids RB(OH)2[R = phenyl, 2,4-difluorophenyl, 4-aminophenyl, 2-thiopheneetc.] underwentipso-hydroxylation smoothly at room temperature to generate the corresponding phenols in excellent yields. The main advantages of this protocol are the aqueous medium reaction, heterogeneous catalytic system, and short reaction time with excellent yield.

Molecular cloning and high-level expression of a β-galactosidase gene from Paecilomyces aerugineus in Pichia pastoris

Katrolia, Priti,Yan, Qiaojuan,Jia, Huiyong,Li, Yinan,Jiang, Zhengqiang,Song, Chunlei

, p. 112 - 119 (2011)

A β-galactosidase gene (designated PaGalA) was cloned for the first time from Paecilomyces aerugineus and expressed in Pichia pastoris under the control of the AOX1 promoter. The coding region of 3036 bp encoded a protein of 1011 amino acids with a deduced molecular mass of 108.7 kDa. The PaGalA without the signal peptide was cloned into a vector pPIC9K and was expressed successfully in P. pastoris as active extracellular β-galactosidase. The recombinant β-galactosidase (PaGalA) was secreted into the medium at an extremely high levels of 22 mg ml-1 having an activity of 9500 U ml-1 from high density fermentation culture, which is by far the highest yield obtained for a β-galactosidase. The purified enzyme with a high specific activity of 820 U mg-1 had a molecular mass of 120 kDa on SDS-PAGE. PaGalA was optimally active at pH 4.5 and a temperature of 60 °C. The recombinant β-galactosidase was able to hydrolyze lactose efficiently at pH 5.0 and 50 °C. It also possessed transglycosylation activities at high concentrations of lactose. PaGalA exhibited better lactose hydrolysis efficiency in whey than two other widely used commercial lactases. The extremely high expression levels coupled with favorable biochemical properties make this enzyme highly suitable for commercial purposes in the hydrolysis of lactose in milk or whey.

Cellulose as recyclable organocatalyst for ipso-hydroxylation of arylboronic acids

Laskar, Khairujjaman,Paul, Subham,Bora, Utpal

, (2019)

Cellulose catalyzed oxidative hydroxylation of aryl and hetero-arylboronic acids to the corresponding phenols under metal and base free strategy has been demonstrated. The sustainable ipso-hydroxylation takes place using hydrogen peroxide as an oxidant in water under mild condition in shorter period of time. Interestingly, easy recovery and reusability of heterogeneous catalyst without significant loss in catalytic yield makes the protocol environmentally benign.

Di- and trinuclear Zn2+ complexes of calix[4]arene based ligands as catalysts of acyl and phosphoryl transfer reactions

Cacciapaglia, Roberta,Casnati, Alessandro,Mandolini, Luigi,Reinhoudt, David N.,Salvio, Riccardo,Sartori, Andrea,Ungaro, Rocco

, p. 624 - 630 (2005)

(Chemical Equation Presented) The calix[4]arene scaffold, blocked in the cone conformation by proper alkylation of the lower rim hydroxyls, was used as a convenient molecular platform for the design of bi- and trimetallic Zn 2+ catalysts. The catalytic activity of the Zn2+ complexes of calix[4]arenes decorated at the 1,2-, 1,3-, and 1,2,3-positions of the upper rim with 2,6-bis[(dimethylamino)methyl]pyridine units were investigated in the cleavage of ester 6 and of the RNA model compound HPNP. High rate enhancements, up to 4 orders of magnitude, were observed in a number of catalyst-substrate combinations. Interestingly the order of catalytic efficiency among regioisomeric dinuclear complexes in the cleavage of ester 6 is 1,2-vicinal ? 1,3-distal, but it is reversed in the reaction of HPNP. The higher efficiency of trinuclear compared to dinuclear complexes provides an indication of the cooperation of three Zn2+ ions in the catalytic mechanism.

In situ generation and synthetic applications of anhydrous hydrogen fluoride in a solid-liquid biphasic system

Rothenberg, Gadi,Royz, Michael,Arrad, Onn,Sasson, Yoel

, p. 1491 - 1494 (1999)

The HI situ generation of anhydrous HF by reaction of solid CaF2 with H2SO4 in the presence of an organic phase containing the substrate is proposed as a simple and safe alternative to other fluorination methods. Using this method, the addition of HF to olefins to produce fluoroalkanes, the substitution of hydroxy and halide functional groups by F atoms, and the conversion of anilines to fluorobenzenes, proceed with good conversions and moderate yields. In the latter reaction, HF generation, diazotization and fluoro de-diazonization can all be carried out in one pot. Reactions can be performed at ambient temperatures and pressures. HF generation using NaF or KF as fluoride sources is less efficient due to formation of stable bifluorides. Lipophilic quaternary ammonium salts such as tetra-octylammonium bromide can be used to enhance the extraction of HF into the organic phase. The effects of solvent nature and reagent ratios are discussed.

A continuous-flow system for high-precision kinetics using small volumes

Zhou, Xianzhi,Medhekar, Rohit,Toney, Michael D.

, p. 3681 - 3687 (2003)

A generally applicable continuous-flow kinetic analysis system that gives data of a precision high enough to measure small kinetic isotope effects for enzymatic and nonenzymatic reactions is described. It employs commercially available components that are readily assembled into an apparatus that is easy to use. It operates under laminar flow conditions, which requires that the time between the initiation of the reaction in the mixer and the observation be long enough that molecular diffusion can effect a symmetrization of the concentration profile that results from a thin plug of reagents introduced at the mixer. The analysis of a second-order irreversible reaction under pseudo-first-order conditions is presented. The Yersinia pestis protein tyrosine phosphatase catalyzed hydrolysis of p-nitrophenyl phosphate is characterized with the system, and a proton inventory on kcat is presented.

Reactivity of typical solvolytic reactions in SDS and TTABr water-in-oil microemulsions

Garcia-Rio,Leis,Reigosa

, p. 5514 - 5520 (1997)

The kinetics of the solvolysis reactions of diphenylmethyl chloride, 4-nitrophenyl chloroformate, benzoyl chloride, anisoyl chloride, and bis(4-nitrophenyl)carbonate were studied in isooctane/SDS/1-hexanol/water and isooctane/TTABr/1-hexanol/water microemulsions with a constant [1-hexanol]/[surfactant] ratio of 5. The results were interpreted by means of a pseudophase model for (isooctane+hexanol)/(surfactant+hexanol)/water systems, the distribution of hexanol between isooctane and surfactant being calculated from previously published data. The intrinsic rate constant for the reaction in the interfacial pseudophase varied with the water content of the microemulsion droplets in a way that depended on both the nature of the surfactant and the mechanism of the reaction.

KINETIC PROPERTIES OF &β-GLUCOSIDASE FROM CASSAVA

Yeoh, Hock-Hin

, p. 721 - 724 (1989)

Key Word Index--Manihot esculenta; cassava; β-glucosidase; linamarase; Km values; inhibition kinetics.Abstract--β-Glucosidases from the leaf, peel and tuber cortex of cassava cv.Merah Jambu exhibited linamarase activity and had in common many kinetic properties.They were also capable of hydrolysing p-nitrophenyl-β-D-monoglycosides and cyanogenic β-monoglucosides but lacked activity towards the p-nitrophenyl-β-D-diglycosides, a cyanogenic diglucosides, and other β- or α-linked disaccharides.The Km values for p-nitrophenyl-β-D-monoglycosides were generally lower than those for linamarin, prunasin and salicin.Ag(2+) inhibited both β-glucosidase and linamarase activities.Glucono-1,5-lactone inhibited the enzyme competitively, irrespective of the substrates used, while imidazole showed competitive inhibition with linamarin but non-competitive (mixed) inhibition with p-nitrophenyl-β-D-glucoside.The enzym was unaffected by glucose.

Mechanistic insights and kinetic analysis for the oxidative hydroxylation of arylboronic acids by visible light photoredox catalysis: A metal-free alternative

Pitre, Spencer P.,McTiernan, Christopher D.,Ismaili, Hossein,Scaiano, Juan C.

, p. 13286 - 13289 (2013)

The photocatalytic hydroxylation of boronic acids with methylene blue as photosensitizer proceeds with high efficiency. Detailed time-resolved studies of the relevant rate constants provide a clear mechanistic understanding of excited-state processes and

Aqueous biphasic oxidation: A water-soluble polyoxometalate catalyst for selective oxidation of various functional groups with hydrogen peroxide

Sloboda-Rozner, Dorit,Witte, Peter,Alsters, Paul L.,Neumann, Ronny

, p. 339 - 345 (2004)

A "sandwich" type polyoxometalate, Na12[(WZn 3(H2O)2][(ZnW9O34) 2], was used as an oxidation catalyst in aqueous biphasic reaction media to effect oxidation of alcohols, diols, pyridine derivatives, amines and aniline derivatives with hydrogen peroxide. The catalyst was shown by 183W NMR to be stable in aqueous solutions in the presence of H 2O2 and showed only minimal non-productive decomposition of the oxidant. Secondary alcohols were selectively oxidized to ketones, while primary alcohols tended to be oxidized to the corresponding carboxylic acids, although secondary alcohols were selectively oxidized in the presence of primary alcohols. Vicinal diols yielded carbon-carbon bond cleavage products in very high yields. Pyridine derivatives were oxidized to the respective TV-oxides, but strongly electron-withdrawing moieties inhibited the oxidation reaction. Primary amines were oxidized to the oximes, but significantly hydrolyzed in situ. Aniline derivatives were oxidized to the corresponding azoxy or nitro products depending on the substitution pattern in the aromatic ring. Catalyst recovery and recycle was demonstrated.

Calcium ion-dependent increase in thermostability of dextran glucosidase from streptococcus mutans

Kobayashi, Momoko,Hondoh, Hironori,Mori, Haruhide,Saburi, Wataru,Okuyama, Masayuki,Kimura, Atsuo

, p. 1557 - 1563 (2011)

Dextran glucosidase from Streptococcus mutans (SmDG), which belongs to glycoside hydrolase family 13 (GH13), hydrolyzes the non-reducing terminal glucosidic linkage of isomaltooligosaccharides and dextran. Thermal deactivation of SmDG did not follow the s

Chemically Modified Chitosan as a Biopolymer Support in Copper-catalyzed ipso-Hydroxylation of Arylboronic Acids in Water

Joo, Seong-Ryu,Kwon, Gyu-Tae,Park, Soo-Youl,Kim, Seung-Hoi

, p. 465 - 468 (2019)

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Inhibition of AcpA phosphatase activity with ascorbate attenuates Francisella tularensis intramacrophage survival

McRae, Steven,Pagliai, Fernando A.,Mohapatra, Nrusingh P.,Gener, Alejandro,Mahmou, Asma Sayed Abdelgeliel,Gunn, John S.,Lorca, Graciela L.,Gonzalez, Claudio F.

, p. 5171 - 5177 (2010)

Acid phosphatase activity in the highly infectious intracellular pathogen Francisella tularensis is directly related with the ability of these bacteria to survive inside host cells. Pharmacological inactivation of acid phosphatases could potentially help

Substrate Specificity in Ester Hydrolysis by a New Water-Soluble Heterocyclophane

Tabushi, Iwao,Kimura, Yoshio,Yamamura, Kazuo

, p. 6486 - 6492 (1981)

A new water-soluble heterocyclophane, N,N,N',N',N'',N'',N''',N'''-octamethyl-2,11,20,29-tetraazaparacyclophanetetrammonium tetrafluoroborate (1), was found to catalyze the hydrolysis reaction of three aromatic chloroacetates, ClCH2CO2R , very effectively and specifically.The rate accelerations judged from the rate constant ratio of k2/k0 were 25+/-3 (7c), 6+/-0.5 (7b), or 2.6 (7a) at pH 8.10 in phosphate buffer and 18+/-2 (7c), 11+/-1 (7b), or 2.4 (7a) at pH 6.96 in phosphate buffer, strongly indicating that the "inclusion-electrostatic" catalyst 1 is more effective and discriminating than any of CTAB micelle, simple cyclodextrin inclusion, or an open-chain analogue (9).Very interestingly, however, a unique inhibition by 1 was found with a substrate of the α-chloro-β-naphthyl type (14), showing a rate constant ratio of kinh/k0=0.084+/-0.023 (1/12 deceleration).In order to elucidate the basis of this interesting discriminative catalysis or inhibition by 1, mechanistic studies were carried out.Temperature-jump experiments by the use of a model compound for substrate, sodium hydroxynaphthalenecarboxylate (11,12), had shown that the present host-guest inclusions are satisfactorily fast (kA=1.8E7 to 4.4E7 s-1 M-1; kD=1.6E4 to 3.8E4 s-1), allowing the host and guest to search for the most appropriate arrangement for the slow subsequent hydrolysis.The absence of any systematic correlation between log (k2/k0) vs. pKa of the leaving phenol or naphthol or a small basicity dependence of the N+-aryloxyl interaction leads to the conclusion that the very discriminative catalysis by 1 was developed mostly from specific substrate binding, in a sense that the N+-oxyanion interaction, at the transition state for the tetrahedral intermediate formation, remarkably depends on the substrate structure.The one-twelfth deceleration observed for 14 was, therefore, attributed to the inhibition of this N+-oxyanion interaction due to either the mechanism of "reverse binding" of the substrate or the "induced disfit".

Facile and selective deprotection of aryl acetates using sodium perborate under mild and neutral conditions

Bandgar, Babasaheb P.,Uppalla, Lavkumar S.,Sadavarte, Vaibhav S.,Patil, Suresh V.

, p. 1273 - 1276 (2002)

A variety of aryl acetates are cleaved to the corresponding phenols using sodium perborate in methanol under mild conditions (25°C). The effectiveness of this protocol is manifested in its tolerance of different functional groups and selectivity of deprotection towards aryl acetates whereas alkyl acetates are found to be unreactive under these reaction conditions.

Fungalα-arabinofuranosidases of glycosyl hydrolase families 51 and 54 show a dual arabinofuranosyl- and galactofuranosyl-hydrolyzing activity

Tefsen, Boris,Lagendijk, Ellen L.,Park, Joohae,Akeroyd, Michiel,Schachtschabel, Doreen,Winkler, Robert,Van Die, Irma,Ram, Arthur F.J.

, p. 767 - 775 (2012)

Aspergillus niger possesses a galactofuranosidase activity, however, the corresponding enzyme or gene encoding this enzyme has never been identified. As evidence is mounting that enzymes exist with affinity for both arabinofuranose and galactofuranose, we

Selective reductive cleavage of inert aryl C-O bonds by an iron catalyst

Ren, Yunlai,Yan, Mengjie,Wang, Jianji,Zhang, Z. Conrad,Yao, Kaisheng

, p. 12674 - 12678 (2013)

Breaking point: An effective reductive cleavage of inert aryl C-O bonds with an inexpensive iron catalyst has been developed. During this process, the reduction of the arene rings was not observed. This catalytic system also enabled the selective cleavage of the β-O-4 linkage of lignin model compounds under an atmosphere of hydrogen, thus offering an opportunity for the depolymerization of lignin. Copyright

Alcohol oxidation in ionic liquid with UHP and recyclable amberlite IR-120 acidic resin: A green approach

Bhati, Nishi,Sarma, Kuladip,Goswami, Amrit

, p. 496 - 497 (2008)

Amberlite IR-120 acidic resin, an age old polymer matrix, plays a significant role as catalyst in the oxidation of aromatic alcohols with urea-hydrogen peroxide in ionic liquid at 70°C to disproportionate into phenols and carbonyl compounds in 30-60 min following two pathways. Under similar condition tertiary aromatic alcohol gave exclusively monohydroxyphenol accompanied by acetone. However, aliphatic and alicyclic alcohols yielded carbonyl compounds in moderate to good yields in 1-5 h. Copyright

Xylella fastidiosa esterase rather than hydroxynitrile lyase

Torrelo, Guzman,Ribeiro De Souza, Fayene Zeferino,Carrilho, Emanuel,Hanefeld, Ulf

, p. 625 - 630 (2015)

In 2009, we reported that the product of the gene SCJ21.16 (XFa0032) from Xylella fastidiosa, a xylem-restricted plant pathogen that causes a range of diseases in several important crops, encodes a protein (XfHNL) with putative hydroxynitrile lyase activi

Highly efficient synthesis of phenols by copper-catalyzed oxidative hydroxylation of arylboronic acids at room temperature in water

Xu, Jimin,Wang, Xinyan,Shao, Changwei,Su, Deyong,Cheng, Guolin,Hu, Yuefei

, p. 1964 - 1967 (2010)

Figure presented A general and efficient procedure for the preparation of phenols was developed by copper-catalyzed oxidative hydroxylation of arylboronic acids at room temperature in water.

A versatile approach for the synthesis of para -substituted arenes via palladium-catalyzed C-H functionalization and protodecarboxylation of benzoic acids

Pan, Shulei,Zhou, Bo,Zhang, Yanghui,Shao, Changdong,Shi, Guangfa

, p. 277 - 281 (2016)

While a great number of ortho C-H functionalization reactions have been developed and several breakthroughs have been achieved in meta C-H activation, para C-H functionalization is still in its infancy stage. In this article, a versatile strategy for the synthesis of para-substituted arenes has been developed via a tandem process consisting of palladium-catalyzed C-H functionalization and subsequent copper-catalyzed protodecarboxylation of benzoic acids. Both electron-withdrawing and electron-donating functionalities can be introduced into the para positions of arenes bearing a variety of substituents.

Novel CuCl2-cryptand-[2.2.Benzo] complex: A base free and oxidant free catalyst for Ipso-Hydroxylation of aryl/heteroaryl-boronic acids in water at room temperature

Bora, Sankar Jyoti,Chetia, Bolin

, p. 52 - 56 (2017)

A novel cryptand and its copper complex was synthesised, which found to have enormous catalytic activity towards ipso-hydroxylation of aryl or heteroarylboronic acids and esters in water without using H2O2 or other oxidising agent and base at room temperature. This newly developed method efficiently converts aryl boronic acids and esters as well as heteroaryl boronic acids to their corresponding phenols with high yields within a very short reaction time. This protocol has found to be well-matched with a wide variety of functional groups. High yields, very short reaction time, easy separation, recyclability up to 6th time are the advantages of this method.

Origin of the dendritic effect in multivalent enzyme-like catalysts

Zaupa, Giovanni,Scrimin, Paolo,Prins, Leonard J.

, p. 5699 - 5709 (2008)

Functionalization of multivalent structures such as dendrimers and monolayer passivated nanoparticles with catalytically active groups results in very potent catalysts, a phenomenon described as the positive dendritic effect. Here, we describe a series of

Glycosyl azide - A novel substrate for enzymatic transglycosylations

Fialová, Pavla,Carmona, Ana T.,Robina, Inmaculada,Ettrich, Rüdiger,Sedmera, Petr,P?ikrylová, Věra,Petrásková-Hu?áková, Lucie,K?en, Vladimír

, p. 8715 - 8718 (2005)

Glycosyl azides are new efficient donors for glycosidases. Their high water solubility facilitates transglycosylations with comparable or better yields than common O-glycosides. The azido group totally changes the β-GalNAc-ase/β-GlcNAc-ase ratio in β-N-ac

Modulation of catalytic functionality of alkaline phosphatase induced by semiconductor quantum dots: Evidence of substrate-mediated protection

Ghosh, Debasmita,Roy, Chandra Nath,Mondal, Somrita,Kundu, Somashree,Maiti, Susmita,Bag, Prasanta Kumar,Saha, Abhijit

, p. 5024 - 5031 (2016)

Enzymes provide the critical means by which almost all biological reactions are catalyzed in a controlled manner. Methods to harness and exploit their properties are of strong current interest to the growing field of biotechnology. In view of many unique

Deacylation Effect in the Hydrolysis of p-Nitrophenyl Esters by Bifunctional Comicelles Containing Imidazolyl and Hydroxyl Groups

Ihara, Yasuji,Nango, Mamoru,Koga, Joichi

, p. 815 - 817 (1987)

The rate constants for hydrolysis of p-nitrophenyl acetate, hexanoate, and dodecanoate catalyzed by bifunctional catalysts containing the imidazolyl and hydroxyl groups have been determined in the presence of hexadecyltrimethylammonium bromide micelles at

Reactions of aryl chlorothionoformates with quinuclidines. A kinetic study

Castro, Enrique A.,Aliaga, Margarita,Campodonico, Paola R.,Leis, J. Ramon,Garcia-Rio, Luis,Santos, Jose G.

, p. 102 - 107 (2008)

The reactions of quinuclidines with phenyl, 4-chlorophenyl, 4-cyanophenyl, and 4-nitrophenyl chlorothionoformates (1, 2, 3, and 4, respectively) are subjected to a kinetic study in aqueous solution, at 25.0°C, and an ionic strength of 0.2 M (KCl). The rea

A MILD PROCEDURE FOR HYDROLYSIS OF ALKOXYMETHYL ARYL ETHERS TO GIVE HYDROXYARENES. A RATIONAL SYNTHESIS OF ASCOFURANONE

Saimoto, Hiroyuki,Kusano, Yukari,Hiyama, Tamejiro

, p. 1607 - 1610 (1986)

A mild procedure is reported for cleavage of alkoxymethyl aryl ethers with P2I4 to afford hydroxyarenes, and this deprotection method was successfully applied to the synthesis of an antibiotic ascofuranone through a rational approach.

Development of a bioautographic method for the detection of lipase inhibitors

Bayineni, Venkata Krishna,Suresh, Sukrutha,Singh, Gurmeet,Kadeppagari, Ravi-Kumar

, p. 784 - 786 (2014)

An autobiographic method based on the thin layer chromatogram was developed by using the chemical system that comprises p-Nitrophenyl butyrate and bromothymol blue for detecting the lipase inhibitor. Lipase inhibitory zones were visualized as blue spots a

New 14-membered trans-di-substituted 'tet-a' macrocycles and their copper(II) and nickel(II) complexes: Spectral, magnetic, electrochemical, crystal structure, catalytic and antimicrobial studies

Nirmala,Kalilur Rahiman,Sreedaran,Jegadeesh,Raaman,Narayanan

, p. 91 - 100 (2011)

Copper(II) and nickel(II) complexes of new trans-di-substituted macrocyclic ligands incorporating three different benzoyl groups, 1,8-bis-(benzoyl)-5,5,7, 12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L1), 1,8-bis-(2-nitrobenzoyl)-5,5,7,12,12,14-hexamethyl-1,4,8,11- tetraazacyclotetradecane (L2), and 1,8-bis-(4-nitrobenzoyl)-5,5,7,12, 12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L3) have been synthesized. The ligands and complexes were characterized by elemental and spectral analysis. Further, the X-ray crystal structure of one of the ligand, L1, has been determined. N-benzoylation causes red shift in the λmax values of the complexes. The cyclic voltammogram of the complexes of ligand L1 shows one-electron, quasi-reversible reduction wave in the region -0.94 to -1.00 V, whereas that of L2 and L 3 show two quasi-reversible reduction peaks corresponding to ligand and metal. Nickel complexes show one electron quasi-reversible oxidation wave at a positive potential in the range +0.92 to +1.21 V. The Cu(II) complexes have a magnetic moment value close to the spin-only value with four hyperfine EPR signals. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts and on the hydrolysis of 4- nitrophenylphosphate using the copper(II) and nickel(II) complexes as catalysts were carried out. The complexes containing electron-withdrawing group shows higher rate-constant values than that with no electron-withdrawing group. All the complexes were screened for antifungal and antibacterial activity.

Probing the role of the trivalent metal in phosphate ester hydrolysis: Preparation and characterization of purple acid phosphatases containing AlIIIZnII and InIIIZnII active sites, including the first example of

Merkx, Maarten,Averill, Bruce A.

, p. 6683 - 6689 (1999)

Purple acid phosphatases contain a dinuclear Fe3+M2+ center in their active site (M = Fe2+ or Zn2+). To resolve the specific role of the ferric ion in catalysis, a series of metal-substituted forms of bovine spl

Structure-Reactivity Relationships in Nucleophilic Reactions on Cinnamoyl Azide and Phenyl Cinnamates. Kinetic Stability of the Acyl Azide and Relative Leaving Ability of Nitrogen and Oxygen

Suh, Junghun,Lee, Byung Hyun

, p. 3103 - 3107 (1980)

The alkaline hydrolysis and aminolysis of cinnamoyl azide and aryl-substituted phenyl cinnamates and the azidolysis of the phenyl cinnamates have been studied.The positions of the rate-determining steps in the reactions are identified by the structure-reactivity relationships.The enhanced affinity of azide ion for an acyl carbon compared with its basicity is proposed to account for the observed kinetic stability of cinnamoyl azide toward alkaline hydrolysis and aminolysis.Azide ion resists expulsion from the tetrahedral intermediate more than quinuclidine derivatives but less than phenolates.This is explained in terms of the electron withdrawal as well as electron donation by resonance.

Effect of high-pressure processing on activity and structure of alkaline phosphatase and lactate dehydrogenase in buffer and milk

Kouassi, Gilles K.,Anantheswaran, Ramaswamy C.,Knabel, Stephen J.,Floros, John D.

, p. 9520 - 9529 (2007)

Changes in the activity and structure of alkaline phosphatase (ALP) and L-lactate dehydrogenase (LDH) were investigated after high pressure processing (HPP). HPP treatments (206-620 MPa for 6 and 12 min) were applied to ALP and LDH prepared in buffer, fat-free milk, and 2% fat milk. Enzyme activities were measured using enzymatic assays, and changes in structure were investigated using far-ultraviolet circular dichroism (CD) spectroscopy and dynamic light scattetering (DLS). Kinetic data indicated that the activity of ALP was not affected after 6 min of pressure treatments (206-620 MPa), regardless of the medium in which the enzyme was prepared. Increasing the processing time to 12 min did significantly reduce the activity of ALP at 620 MPa (P 0.001). However, even the lowest HPP treatment of 206 MPa induced a reduction in LDH activity, and the course of reduction increased with HPP treatment until complete inactivation at 482, 515, and 620 MPa. CD data demonstrated a partial change in the secondary structure of ALP at 620 MPa, whereas the structure of LDH showed gradual denaturation after exposure at 206 MPa for 6 min, leading to a random coil structure at both 515 and 620 MPa. DLS results indicated aggregation of ALP only at HPP treatment of 206 MPa and not above and enzyme precipitation as well as aggregation at 345, 415, 482, and 515 MPa. The loss of LDH activity with increasing pressure and time treatment was due to the combined effects of denaturation and aggregation.

The Reactivity of p-Nitrophenyl Esters with Surfactants in Apolar Solvents. V. p-Nitrophenyl Acetate in Benzene Solutions of Butane-1,4-diamine Bis(dodecanoate)

O'Connor, Charmian J.,Lomax, Terence D.

, p. 895 - 905 (1983)

The rate of decomposition of p-nitrophenyl acetate in benzene in the presence of butane-1,4-diamine bis(dodecanoate) (budb) has been measured at temperatures between 333 and 353 K.The data fit a rate equation which consists of a term arising from micellar

Comparisons of phosphorothioate with phosphate transfer reactions for a monoester, diester, and triester: Isotope effect studies

Catrina, Irina E.,Hengge, Alvan C.

, p. 7546 - 7552 (2003)

Phosphorothioate esters are sometimes used as surrogates for phosphate ester substrates in studies of enzymatic phosphoryl transfer reactions. To gain better understanding of the comparative inherent chemistry of the two types of esters, we have measured equilibrium and kinetic isotope effects for several phosphorothioate esters of p-nitrophenol (pNPPT) and compared the results with data from phosphate esters. The primary 18O isotope effect at the phenolic group (18kbridge), the secondary nitrogen-15 isotope effect (15k) in the nitro group, and (for the monoester and diester) the secondary oxygen-18 isotope effect (18knonbridge) in the phosphoryl oxygens were measured. The equilibrium isotope effect (EIE) 18knonbridge for the deprotonation of the monoanion of pNPPT is 1.015 ± 0.002, very similar to values previously reported for phosphate monoesters. The EIEs for complexation of Zn2+ and Cd2+ with the dianion pNPPT2- were both unity. The mechanism of the aqueous hydrolysis of the monoanion and dianion of pNPPT, the diester ethyl pNPPT, and the triester dimethyl pNPPT was probed using heavy atom kinetic isotope effects. The results were compared with the data reported for analogous phosphate monoester, diester, and triester reactions. The results suggest that leaving group bond fission in the transition state of reactions of the monoester pNPPT is more advanced than for its phosphate counterpart pNPP, while alkaline hydrolysis of the phosphorothioate diester and triester exhibits somewhat less advanced bond fission than that of their phosphate ester counterparts.

-

Epshtein,L.M. et al.

, (1975)

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Preparation of a PTE simulacrum based on surface molecular imprinting

Guo, Yong,Yang, Ying,Guo, Tian Ying

, p. 493 - 496 (2011)

Firstly, we synthesized N-methacryloyl-histidine monomer and N-methacryloyl-histidine-Cu2+ complex (MAH-Cu2+). Then the molecular imprinting polymers (MIP) has been prepared by surface grafting on uniform polystyrene (PS) core using

Entropy and Enthalpy Contributions to Solvent Effects on Phosphate Monoester Solvolysis. The Importance of Entropy Effects in the Dissociative Transition State

Hoff, Richard H.,Hengge, Alvan C.

, p. 6680 - 6688 (1998)

The solvolysis reactions of a series of aryl phosphates in tert-butyl alcohol and in tert-amyl alcohol have been examined. The dianion of p-nitrophenyl phosphate reacts 7500- and 8750-fold faster in these solvents, respectively, than the corresponding aqu

Reaction of poly-L-lysine with aryl acetates and aryl methyl carbonates. A mechanistic study

Castro, Enrique A.,Echevarria, Gerardo R.,Opazo, Alejandra,Robert, Paz S.,Santos, Jose G.

, p. 62 - 67 (2008)

The pH profile (log k vs. pH) of the reactions of poly-L-lysine (PL) with a series of aryl acetates and aryl methyl carbonates in aqueous solution show the same conformational changes as those determined by potentiometric titrations. When PL is a random coil, the most probable mechanism for the reactions studied is through the formation of a tetrahedral intermediate and its breakdown to products as the rate-determining step. The tetrahedral intermediate is stabilized by a hydrogen bond interaction between the nitro groups in the substrate and the NH group of the principal chain or some NH2 groups of the lateral chains. Copyright

Nickel-catalyzed oxidative hydroxylation of arylboronic acid: Ni(HBTC)BPY MOF as an efficient and ligand-free catalyst to access phenolic motifs

Latha, Ganesapandian,Devarajan, Nainamalai,Karthik, Murugan,Suresh, Palaniswamy

, (2020)

A straightforward and mild oxidative ipso-hydroxylation of arylboronic acids has been achieved using a simple and non-noble metal, nickel-based reusable heterogeneous catalyst Ni(HBTC)BPY MOF (HBTC = benzene-1,3,5-tricarboxylate, BPY = 4,4′-bipyridine) in the presence of benign hydrogen peroxide as an oxidant under ambient reaction condition. The Ni(HBTC)BPY MOF exhibits excellent catalytic activity towards the formation of phenols from diverse arylboronic acids within short time and can be reused up to five times without any notable loss in its activity as well as shown high functional group tolerance even in the presence of sensitive functionalities and useful to achieve hydroxyl group in heterocycles.

Effect of Hydrophobic-Lipophilic Interactions on Chemical Reactivity. 6. The First Example of Correlation of Hydrophobic-Lipophilic Substituent Constants with Chemical Reactivity for a Simple Substrate-Solvent System

Fan, Wei-Qiang,Jiang, Xi-Kui

, p. 7680 - 7684 (1985)

Hydrolytic rate constants (kobsd) were determined for 13 para- and meta-substituted phenyl esters of n-hexadecanoates (16-Y) in 55:45 (v/v) (Φ=0.55), 60:40 (Φ=0.60), 65"35 (Φ=0.65), and 70:30 (Φ=0.70) Me2SO-H2O solvent mixtures.Rates of 7 n-octanoates (8-Y) were also measured in solvents with Φ=0.55, 0.60, 0.65.Results reveal that the nature of the substituent effect depends on solvent composition.At Φ=0.70, the log kob's correlate with Hammett's ? constants, whereas at Φ=0.55, they correlate with Rekker's hydrophobic f constants.In between at Φ=o.65 and 0.60, the rate constants can be expressed in terms of a two-parameter equation: log k=?ρ + hf + C.The n-octanoates, as expected, follow only the Hammett correlation in disregard of the solvent composition.The present work is the first example of a successful correlation of hydrophobic-lipophilic substituent constants for substrates with different types of substituents and withuot the involvement of "third-parties", e.g., added host or surfactant molecules.It provides further insights into the effect of hydrophobic-lipophilic interactions on chemical reactivity and yet another new line of evidence for the phenomena of aggregation and self-coiling.

Characterization of a novel thermophilic pyrethroid-hydrolyzing carboxylesterase from Sulfolobus tokodaii into a new family

Wei, Tao,Feng, Shengxue,Shen, Yulong,He, Peixin,Ma, Geli,Yu, Xuan,Zhang, Fei,Mao, Duobin

, p. 225 - 232 (2013)

A novel gene ST2026 encoding a putative carboxylesterase from the thermophilic crenarchaeota Sulfolobus tokodaii (named EstSt7) was cloned and functionally overexpressed in Escherichia coli. The recombinant enzyme was purified to homogeneity after heat treatment, Ni-NTA affinity and Superdex-200 gel filtration chromatography. EstSt7 showed maximum activity at 80 C over 30 min and had a half-life of 180 min at 90 C. Its enzymatic activity was stable in the pH range of 8.0-10.0 with an optimum at 9.0. The enzyme exhibited significant esterase activity toward various p-nitrophenyl esters and the most preferable substrate was p-nitrophenyl butyrate (kcat/Km of 246.3 s-1 mM-1). In addition, EstSt7 showed high activity and stability against organic solvents (20% and 50% v/v) and detergents (1% and 5% v/v). Furthermore, EstSt7 could efficiently hydrolyze a wide range of synthetic pyrethroids including fenpropathrin, permethrin, cypermethrin, cyhalothrin, deltamethrin and bifenthrin, which makes it a potential candidate for the detoxification of pyrethroids for the purpose of biodegradation. Sequence alignment, phylogenetic analysis and comparison of the conserved motif reveal that this novel carboxylesterase EstSt7 should be grouped into a new bacterial lipase and esterase family.

A mechanistic study for 4A1 antibody-catalyzed hydrolysis : Detection of acyl intermediate

Wada, Yumiko,Sudo, Yukio,Ono, Mitsunori

, p. 1225 - 1226 (1997)

Recent study identified a hydrolytic abzyme 4A1, that has a significant rate enhancement in hydrolysis of carbonate substrates differing from the inducing hapten in structure around the scissile bond. Kinetic investigation suggested the existence of other

Polyoxometalates: Study of inhibitory kinetics and mechanism against α-glucosidase

Chi, Guoxiang,Wang, Li,Chen, Bingnian,Li, Jian,Hu, Jingjing,Liu, Shuxia,Zhao, Meijuan,Ding, Xiaomei,Li, Yue

, (2019)

Alpha-glucosidase is considered to be an important target for the treatment of noninsulin-dependent diabetes. In this work, the inhibitory effects of polyoxometalates (POMs) affected by three different factors (heteroatom, transition metal substitution el

Enzymatic synthesis of sulfated disaccharides using β-D-galactosidase-catalyzed transglycosylation

Murata, Takeomi,Kosugi, Masaki,Nakamura, Tadashi,Urashima, Tadasu,Usui, Taichi

, p. 2456 - 2464 (2001)

We have established a unique enzymatic approach for obtaining sulfated disaccharides using Bacillus circulans β-D-galactosidase-catalyzed 6-sulfo galactosylation. When 4-methyl umbelliferyl 6-sulfo β-D-galactopyranoside (S6Gal β-4MU) was used as a donor, the enzyme induced transfer of 6-sulfo galactosyl residue to GlcNAc acceptor. As a result, the desired compound 6′-sulfo N-acetyllactosamine (S6Gal β1-4GlcNAc) and its positional isomer 6′-sulfo N-acetylisolactosamine (S6Gal β1-6GlcNAc) were observed by HPAEC-PAD, in 49% total yield based on the donor added, and in a molar ratio of 1:3.5. With a glucose acceptor, the regioselectivity was substantially changed and S6Gal β1-2Glc was mainly produced along with β-(1-1)α, β-(1-3), β-(1-6) isomers in 74% total yield. When methyl α-D-glucopyranoside (Glcα-OMe) was an acceptor, the enzyme also formed mainly S6Gal β1-2Glcβ-OMe with its β-(1-6)-linked isomer in 41% total yield based on the donor added. In both cases, it led to the predominant formation of β-(1-2)-linked disaccharides. In contrast, with the corresponding methyl β-D-glucopyranoside (Glc β-OMe) acceptor, S6Gal β1-3Glc β-OMe and S6Gal β1-6Glc β-OMe were formed in a low total yield of 12%. These results indicate that the regioselectivity and efficiency on the β-D-galactosidase-mediated transfer reaction significantly depend on the anomeric configuration in the glucosyl acceptors.

The effect of lecithin dispersed by surfactants on the hydrolysis of p-nitrophenyl acetate

Yotsuyanagi,Mizutani,Ikeda

, p. 137 - 138 (1982)

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Function–Topology Relationship in the Catalytic Hydrolysis of a Chemical Warfare Simulant in Two Zr-MOFs

Ghasempour, Hosein,Morsali, Ali

, p. 17437 - 17444 (2020)

Owing to their high surface area, high concentration of active metal sites, and water stability, zirconium(VI)-based metal–organic frameworks (Zr-MOFs) have shown excellent activity in the hydrolysis of organophosphorus nerve agents (OPNs). In this regard, for the first time, two topologically different Zr-MOFs (Zr-fcu-tmuc and Zr-bcu-tmuc, constructed from the same organic and inorganic building blocks; fcu=face-centered cubic, bcu=body-centered cubic) have been rationally chosen to investigate the effect of network topology on the catalytic hydrolysis of the nerve agent simulant, dimethyl 4-nitrophenyl phosphate (DMNP). A remarkable enhancement in the hydrolysis rate of DMNP was observed with Zr-bcu-tmuc, reducing the half-life more than three-fold compared with Zr-fcu-tmuc. Greater accessibility of the active ZrVI sites in the 8-connected bcu net compared with the 12-connected fcu leads to a faster hydrolysis of DMNP on Zr-bcu-tmuc. Interestingly, the higher activity of Zr-bcu-tmuc was also confirmed by its higher fluorescence sensitivity towards DMNP (limit of detection (LOD)=0.557 μm) compared with Zr-fcu-tmuc (LOD=1.09 μm). The results show that controlling the desired topology of Zr-MOFs is a useful strategy for improving their performance in the detection and catalytic detoxification of OPNs.

Aryl sulfatase of unusual specificity from the liver of marine mollusk Littorina kurila

Kusaykin,Pesentseva,Sil'Chenko,Avilov,Sova,Zvyagintseva,Stonik

, p. 63 - 70 (2006)

An aryl sulfatase of unusual specificity has been isolated from the liver of marine mollusk Littorina kurila. It hydrolyzes p-nitrophenyl sulfate, does not affect the natural fucoidan, and catalyzes splitting off the sulfate group in position C4 of xylose

-

Brasem et al.

, p. 685 (1972)

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REACTIVITY AND STEREOSELECTIVITY IN THE CLEAVAGE OF COMPLEXES OF ACTIVATED ENANTIOMERIC SUBSTRATES WITH CYCLODEXTRINS.

Fornasier, Roberto,Scrimin, Paolo,Tonellato, Umberto

, p. 5541 - 5542 (1983)

Remarkable rate accelerations and enantioselectivities in the cleavage of the enantiomers of carbonate 1 and of ester 2 in the presence of α- and β-cyclodextrins are reported.

Mechanism of Meerwein arylation of furan derivatives

Obushak,Lesyuk,Gorak, Yu. I.,Matiichuk

, p. 1375 - 1381 (2009)

Catalytic arylation of furan-2-carbaldehyde with arenediazonium salts was studied. The yields of 5-arylfuran-2-carbaldehydes were found to depend on the solvent, catalyst, and anion in the arenediazonium salt. Redox catalysis and generation of aryl radicals are not sufficient conditions for the reaction to occur. The reaction is successful only under conditions ensuring formation of complex intermediates. A mechanism involving two Cu2+ ? Cu + catalytic series and generation of furan-2-carbaldehyde was proposed.

Substrate recognition and saturation kinetics in de novo designed histidine-based four-helix bundle catalysts

Broo, Kerstin S.,Nilsson, Helena,Nilsson, Jonas,Baltzer, Lars

, p. 10287 - 10295 (1998)

Designed four-helix bundle proteins with reactive sites based on the cooperativity of HisH+-His pairs in helical sequences catalyze acyl-transfer reactions of p-nitrophenyl esters with large rate enhancements. The function of the HisH+/su

Microbial biocatalysis of quercetin-3-glucoside and isorhamnetin-3-glucoside in: Salicornia herbacea and their contribution to improved anti-inflammatory activity

Ahn, Hyung Jin,Choe, Deokyeong,Ji, Geun Eog,Johnston, Tony Vaughn,Ku, Seockmo,Li, Zhipeng,Park, Myeong Soo,You, Hyun Ju

, p. 5339 - 5350 (2020)

Salicornia herbacea (glasswort) is a traditional Asian medicinal plant which exhibits multiple nutraceutical and pharmaceutical properties. Quercetin-3-glucoside and isorhamnetin-3-glucoside are the major flavonoid glycosides found in S. herbacea. Multipl

Catalysis of hydrolysis and transesterification reactions of p- Nitrophenyl esters by a designed helix-loop-helix dimer

Broo, Kerstin S.,Brive, Lars,Ahlberg, Per,Baltzer, Lars

, p. 11362 - 11372 (1997)

KO-42, a polypeptide with 42 amino acid residues has been designed to fold into a hairpin helix-loop-helix motif that dimerizes and forms a four- helix bundle. The solution structure of the folded KO-42 dimer has, been determined by NMR and CD spectroscop

Comment on 'Formation of nitroaromatic compounds in advanced oxidation processes: Photolysis versus photocatalysis'

Louw,Santoro

, p. 3281 - 3281 (1999)

A discussion on nitrophenols formation from the treatment of waters containing phenol and nitrate, covers the valuable contribution of the recent paper by Dzengel et. al. to the knowledge on scope and limitations of advanced oxidation technologies for the

Acceleration of acid-catalyzed transesterification of 2-hydroxypropyl-p-nitrophenyl phosphate by organic solvents

Hong, In Seok,Suh, Junghun

, p. 377 - 380 (2000)

(Formula Presentation) Transesterification of 2-hydroxypropyl-p-nitrophenyl phosphate in the presence of 0.092 M HClO4 is 50-5000 times faster in acetonitrile, 1,4-dioxane, methanol, ethanol, N,N-dimethylformamide, or dimethyl sulfoxide than in

Cyclodextrin-peptide hybrid as a hydrolytic catalyst having multiple functional groups

Tsutsumi, Hiroshi,Hamasaki, Keita,Mihara, Hisakazu,Ueno, Akihiko

, p. 741 - 743 (2000)

A designed cyclodextrin-peptide hybrid, which has multiple functional groups on its α-helix peptide backbone, has been synthesized as a catalyst for ester hydrolysis. Kinetic study revealed that the carboxylate group plays a key role in this system. (C) 2

Conidial alkaline phosphatase from Neurospora crassa

Say, Jose C.,Furriel, Rosa P.M.,Ciancaglini, Pietro,Jorge, Joao A.,Lourdes, Maria,Polizeli,Pizauro, Joao M.,Terenzi, Hector F.,Leone, Francisco A.

, p. 71 - 75 (1996)

An alkaline phosphatase was purified from conidia of a Neurospora crassa wild type strain. The Mr of the purified native enzyme was estimated as ca 145000 and 110000 by gel filtration, in the presence and absence of magnesium ions, respectively

New processes in the environmental chemistry of nitrite: Nitration of phenol upon nitrite photoinduced oxidation

Pelizzetti,Vione,Maurino,Minero

, p. 669 - 676 (2002)

Nitrite is a relevant environmental factor in natural waters and in the atmosphere. The effects of dissolved Fe(III), α-Fe2O3, β-FeOOH, NO3-, and humic acid on phenol nitration in irradiated systems containing N

PERMEABLE MEMBRANE - MASS SPECTROMETRIC MEASUREMENT OF REACTION KINETICS.

Calvo,Weisenberger,Anderson,Klapper

, p. 981 - 985 (1981)

The compound to be analyzed is introduced into the source of a mass spectrometer after selective permeation through a thin membrane which permits passage of apolar molecules. The in situ measurement of ethyl 2-furoate produced in an alpha -chymotrypsin catalyzed transesterification is described. Under present experimental conditions, and in a selective ion mode operation, ethyl furoate production can be detected with a sensitivity of 0. 1 mu M and a response time of approximately 13 s at 25 degree C.

-

Nucci et al.

, p. 3099 (1977)

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Export of methyl parathion hydrolase to the periplasm by the twin-arginine translocation pathway in escherichia coli

Yang, Chao,Freudl, Roland,Qiao, Chuanling

, p. 8901 - 8905 (2009)

The uptake of organophosphates (OPs) is a rate-limiting factor in whole-cell biocatalysis systems. Here, we report the periplasmic secretion of methyl parathion hydrolase (MPH) by employing the twinarginine translocation (Tat) pathway in Escherichia coli. The twin-arginine signal peptide of trimethy-lamine N-oxide reductase (TorA) from E. coli was used for exporting MPH to the periplasm of E. coli, alleviating the substrate uptake limitation. A periplasmic expression vector, pUTM18, coding for TorA-MPH was constructed, and the periplasmic secretion and functionality of MPH were demonstrated by cell fractionation, immunoblotting, and enzyme activity assays. The strain expressing periplasmic MPH showed 3-fold higher whole-cell activity than the control strain expressing cytoplasmic MPH. Suspended cultures also exhibited good stability, retaining almost 100% activity over a period of 2 weeks. Owing to their high activity and superior stability, these "live biocatalysts" are ideal for large-scale detoxification of OPs.

Transition state stabilization by micelles: the hydrolysis of p-nitrophenyl alkanoates in cetyltrimethylammonium bromide micelles

Tee,Fedortchenko

, p. 1434 - 1438 (1997)

The cleavage of p-nitrophenyl alkanoates (acetate to octanoate) at high pH is modestly catalyzed by micelles formed from cetyltrimethylammonium bromide (CTAB) in aqueous solution. Rate constants exhibit saturation behaviour with respect to [CTAB], consist

Very fast ester hydrolysis by a cyclodextrin dimer with a catalytic linking group

Breslow, Ronald,Zhang, Biliang

, p. 5882 - 5883 (1992)

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Nitration of phenol and substituted phenols with dilute nitric acid using phase-transfer catalysts

Joshi, Ashutosh V.,Baidoosi, Mubeen,Mukhopadhyay, Sudip,Sasson, Yoel

, p. 95 - 97 (2003)

Highly selective nitration of phenol and substituted phenols to the corresponding nitro compounds is accomplished under mild conditions in a liquid - liquid two-phase system with dilute nitric acid (6 wt %) and in the presence of a phase-transfer catalyst. The consequence of various phase-transfer catalysts on the reaction rate is contemplated. Tetrabutylammonium bromide (TBAB) was found to be the most effective phase-transfer catalyst in terms of conversion and selectivity. The experimental results are accounted for by a binary role of the phase-transfer catalyst in this system. It is anticipated to extract nitric acid into the organic phase via the hydrogen-bonded complex and to supply HBr, formed in situ in the reaction scheme by anion exchange, which is believed to be the key for generation of the active nitration species, nitronium ion in the organic phase.

Enzymatic modification of hydroxyethylcellulose by transgalactosylation with β-galactosidases

Li, Jun,Cheng,Nickol, Robert G.,Wang, Peng George

, p. 133 - 137 (1999)

β-galactosidases from A. oryzae and a thermophilic CLONEZYME(TM) glycosidase library were used to catalyze the transfer of the β-D-galactopyranosyl moiety from lactose to the hydroxyl groups of hydroxyethylcellulose (HEC) in sodium acetate buffer. The degree of substitution was quantified by using galactose oxidase enzymatic assays. Depolymerization was also observed in the course of the transglycosylation reactions. Copyright (C) 1999 Elsevier Science Ltd.

Studies on the Susceptibility to Alkaline Hydrolysis of Inclusion Complexes of Organophosphorothioate Pesticides with β-Cyclodextrins

Kamiya, Mamoru,Nakamura, Kaori

, p. 305 - 310 (1994)

The inhibition of alkaline hydrolysis of organophosphorothioate pesticides such as parathion, parathion-methyl and fenitrithion by the formation of inclusion complexes with β-cyclodextrin and its methylated derivatives was investigated. The inclusion complex/pesticide stability relationship with the series of pesticides and β-cyclodextrins is discussed in connection with the inclusion geometrical parameters, such as those relating to the inclusion orientation and depth of the 4-nitrophenoxy moiety of the included pesticide. These parameters were estimated from the induced circular dichroism of the inclusion complexes by means of the rotational-strength analysis method.

Phosphoryl Transfer Processes Promoted by a Trifunctional Calix[4]arene Inspired by DNA Topoisomerase i

Salvio, Riccardo,Volpi, Stefano,Cacciapaglia, Roberta,Sansone, Francesco,Mandolini, Luigi,Casnati, Alessandro

, p. 9012 - 9019 (2016)

The cone-calix[4]arene derivative (1H3)2+, decorated at the upper rim with two guanidinium units and a phenolic hydroxyl in an ABAH functionalization pattern, effectively promotes the cleavage of the DNA model compound bis(p-nitrophe

Purification and characterization of a glucose-tolerant β-glucosidase from black plum seed and its structural changes in ionic liquids

Bi, Yanhong,Zhu, Chun,Wang, Zhaoyu,Luo, Hongzhen,Fu, Ruiping,Zhao, Xiaojuan,Zhao, Xiangjie,Jiang, Ling

, p. 422 - 428 (2019)

The objective of this study was to characterize a plant origin β-glucosidase from black plum seeds and identify its conformational changes in twenty-six imidazolium- and amino acid-based ionic liquids (ILs). The results revealed that the purified 60 kDa e

4-Nitrophenyltriflate as a New Triflating Agent

Zhu, Jieping,Bigot, Antony,Elise, Marie,Dau, Tran Huu

, p. 1181 - 1182 (1997)

Aryl triflates were prepared under mild conditions using 4-nitrophenyl triflate (1) as a stable, crystalline triflating agent.

Application of Electron-Rich Covalent Organic Frameworks COF-JLU25 for Photocatalytic Aerobic Oxidative Hydroxylation of Arylboronic Acids to Phenols

Xiao, Guangjun,Li, Wenqian,Chen, Tao,Hu, Wei-Bo,Yang, Hui,Liu, Yahu A.,Wen, Ke

, p. 3986 - 3991 (2021)

Visible-light-driven organic reactions are environmentally friendly green chemical transformations among which photosynthetic oxidative hydroxylation of arylboronic acids to phenols has attracted increasing research interest during the very recent years. Given the efficiency and reusability of heterogeneous catalysts, COF-JLU25, an electron-rich COF-based photocatalyst constructed by integrating electron-donating blocks 1,3,6,8-tetrakis(4-aminophenyl)pyrene (PyTA) and 4-[4-(4-formylmethyl)-2,5-dimethoxyphenyl] benzaldehyde (TpDA), was selected as a photocatalyst for the oxidative hydroxylation of arylboronic acids. In our studies, COF-JLU25 demonstrated excellent photocatalytic activity with high efficiency, robust reusability, and low catalyst loading, showcasing an application potential of previously underexplored COF-based photocatalyst composed solely of electron-rich units.

(Z)-3-butylidenephthalide from Ligusticum porteri, an α-glucosidase inhibitor

Brindis, Fernando,Rodriguez, Rogelio,Bye, Robert,Gonzalez-Andrade, Martin,Mata, Rachel

, p. 314 - 320 (2011)

An extract from the roots of Ligusticum porteri, orally administered to groups of normal and diabetic mice, showed significant hypoglycemic and antihyperglycemic effects. Experimental type-II DM was achieved by treating mice with streptozotocin 15 min aft

Activity of Lipase in Water-in-oil Microemulsions

Fletcher, Paul D. I.,Robinson, Brian H.,Freedman, Robert B.,Oldfield, Christopher

, p. 2667 - 2680 (1985)

The lipase-catalysed hydrolysis rates of several nitrophenyl alkanoate esters of varying alkyl chain length (C4-C16) have been measured both in aqueous solution and in water-in-oil (w/o) microemulsions (which are known to contain discrete droplets).Lipase

Efficient method for demethylation of aryl methyl ether using aliquat-336

Waghmode, Suresh B.,Mahale, Ganesh,Patil, Viraj P.,Renalson, Kartik,Singh, Dharmendra

, p. 3272 - 3280 (2013)

A rapid method for selective cleavage of aryl methylethers can be achieved in the presence of a protic acid and a catalytic amount of phase-transfer catalyst (Aliquat-336). Aliquat-336 accelerates the rate of reaction and affords the corresponding phenols in excellent to good yields on a wide variety of substrates. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.]

The inhibitory role of Co2+ on α-glucosidase: Inhibition kinetics and molecular dynamics simulation integration study

Li, Xuan,Lü, Zhi-Rong,Shen, Dong,Zhan, Yi,Yang, Jun-Mo,Park, Yong-Doo,Zhou, Hai-Meng,Sheng, Qing,Lee, Jinhyuk

, p. 1913 - 1919 (2014)

It is important to study enzyme inhibition of α-glucosidase (EC 3.2.1.20) due to its clinical relevance as a target enzyme for the treatment of type 2 diabetes mellitus. In this study, we investigated Co2+-induced inhibition as well as structur

Quantity of immobilized acid phosphatase and reaction rate across enzyme membranes

Takeda, Hideo,Tanaka, Hiroki,Nomura, Kazuo

, p. 1102 - 1103 (2010)

Acid phosphatase from sweet potato was immobilized on the external-solution side surface of a perfluorocarboxylate ionexchange membrane. Two membranes of different enzyme amounts were prepared without any crosslinking reagents. The effect of the immobiliz

Structure-efficiency relationships of cyclodextrin scavengers in the hydrolytic degradation of organophosphorus compounds

Letort, Sophie,Bosco, Micha?l,Cornelio, Benedetta,Brégier, Frédérique,Daulon, Sébastien,Gouhier, Géraldine,Estour, Fran?ois

, p. 417 - 427 (2017)

New derivatives of cyclodextrins were prepared in order to determine the relative importance of the structural key elements involved in the degradation of organophosphorus nerve agents. To avoid a competitive inclusion between the organophosphorus substra

Hydrolysis of phosphodiester with hydroxo- or carboxylate-bridged dinuclear Ni(II) and Cu(II) complexes

Yamaguchi,Akagi,Fujinami,Suzuki,Shionoya,Suzuki

, p. 375 - 376 (2001)

A hydroxo- or carboxylate-bridged dinuclear Ni(II) complexes with N,N,N′,N′-tetrakis((6-methyl-2-pyridyl)methyl)- 1,3-diaminopropan-2-ol has been synthesized as models for Ni(II)-substituted phosphotriesterase, which are more active catalysts for hydrolys

Mercury(II) Ion-Promoted Hydrolysis of Some Organophosphorus Pesticides

Wan, Hai Bin,Wong, Ming Keong,Mok, Chup Yew

, p. 93 - 100 (1994)

The promotion of hydrolysis of some organophosphorus pesticides by mercury(II) ion was studied. The presence of mercuric chloride at 20 mg litre-1 increased the initial hydrolysis rates of malathion, fenitrothion, fenthion and parathion-methyl in pH 5.5 buffer by two to three orders of magnitude. The hydrolysis was found to be first order with respect to both mercury(II) ion and the pesticide. The main hydrolysis product was 3-methyl-4-nitrophenol for fenitrothion, and 4-nitrophenol for parathion-methyl. It is postulated that the reaction involves the formation of a 1:1 complex and very slow regeneration of the mercury(II) ion from the reacted complex. Mercury(II) ion had little effect on the organophosphorus pecticide dichlorphos.

Electrochemical investigations of lipase enzyme activity inhibition by methyl parathion pesticide: Voltammetric studies

Reddy, K. Gangadhara,Madhavi,Swamy, B.E. Kumara,Reddy, Sathish,Reddy, A.Vijaya Bhaskar,Madhavi

, p. 26 - 30 (2013)

Candida Rugosa Lipase mobilized sensor method was developed for the detection of organophosphorus pesticides like methyl parathion. Here p-Nitrophenyl Acetate was used as a substrate which releases p-Nitrophenol by the enzymatic hydrolysis and gives an an

Synthesis of a peptidocalix[4]arene library and identification of compounds with hydrolytic activity

Brewster, R. Elizabeth,Dalton, Brian G.A.,Shuker, Suzanne Beckham

, p. 16 - 21 (2005)

A 120 member library of peptidocalix[4]arenes was synthesized and screened for catalysis of the hydrolysis of p-nitrophenyl acetate. His-Ser-His-calix[4] arene was found to catalyze this reaction with v0 = 3.24 × 10-8 M/s, an increase of 1520% above background and 30% above the tripeptide (His-Ser-His) alone.

Alkali-metal ion catalysis and inhibition in nucleophilic displacement reactions at carbon, phosphorus and sulfur centres. IX. p-Nitrophenyl diphenyl phosphate

Nagelkerke, Ruby,Thatcher, Gregory R.J.,Buncel, Erwin

, p. 163 - 167 (2003)

We report on the catalytic effects by alkali-metal ions in the ethanolysis of p-nitrophenyl diphenyl phosphate, in continuation of our studies on alkali-metal ion catalysis and inhibition in nucleophilic displacement reactions at carbon, phosphorus and sulfur centres. The following selectivity order of catalytic reactivity was observed for nucleophilic displacement at the phosphorus center with p-nitrophenoxide as leaving group: Li+ > Na+ > K+ > Cs+ A minor reaction pathway with phenoxide leaving was also found. The kobs data have been dissected into reaction pathways by free ions (kEtO) and by ion pairs (kMOEt) with the latter being dominant, in a 4-membered transition-state. Further analysis is given in terms of initial-state and transition-state stabilization by the alkali-metal ions in terms of the Eisenman model (electrostatic interaction vs. desolvation). Results of ab-initio MO calculations are presented based on interaction between M+ and a model bipyramidal phosphorane intermediate and compared with the sulfurane analogue.

Immobilization of α-galactosidase inside hybrid silica nanocomposites containing polysaccharides

Bakunina,Nedashkovskaya,Zvyagintseva,Shchipunov

, p. 827 - 832 (2006)

α-Galactosidase was encapsulated into sol-gel derived hybrid polysaccharide-silica nanocomposites. The main properties of the immobilized enzyme were studied. Pleiades Publishing, Inc., 2006.

Bio-relevant manganese(II) compartmental ligand complexes: Syntheses, crystal structures and studies of catalytic activities

Guha, Averi,Banu, Kazi Sabnam,Banerjee, Arpita,Ghosh, Totan,Bhattacharya, Santanu,Zangrando, Ennio,Das, Debasis

, p. 51 - 57 (2011)

Three new mono-manganese(II) complexes of a compartmental ligand, namely [Mn(HL)(H2O)3](NO3)2·H 2O (1), [Mn(HL)(SCN)2(H2O)]·H 2O (2), and [Mn(HL){N(CN)2}(H

A novel method for the regeneration of alcohols from toluene sulphonates using CeCl3. 7H2O -NaI system

Sudhakar Reddy,Hari Mohan,Iyengar

, p. 3829 - 3832 (2000)

Treatment of aryl and alkyl tosylates with Cerium(III) chloride hepta hydrate and sodium iodide in acetonitrile provides a simple, convenient and chemoselective procedure for the detosylatlon.

Efficient promotion of phosphate diester cleavage by a face-to-face cyclodextrin dimer without metal

Hu, Ping,Liu, Gao-Feng,Ji, Liang-Nian,Mao, Zong-Wan

, p. 5515 - 5517 (2012)

An organic face-to-face cyclodextrin dimer promotes the cleavage of bis(4-nitrophenyl) phosphate efficiently in neutral pH without the addition of metal. Both of the phosphate diester bonds can be cleaved.

Enhancing activity and thermostability of lipase A from Serratia marcescens by site-directed mutagenesis

Mohammadi, Mohsen,Sepehrizadeh, Zargham,Ebrahim-Habibi, Azadeh,Shahverdi, Ahmad Reza,Faramarzi, Mohammad Ali,Setayesh, Neda

, p. 18 - 28 (2016)

Lipases as significant biocatalysts had been widely employed to catalyze various chemical reactions such as ester hydrolysis, ester synthesis, and transesterification. Improving the activity and thermostability of enzymes is desirable for industrial appli

A New Method for Nitration of Phenolic Compounds

Shi, Min,Cui, Shi-Cong

, p. 1197 - 1202 (2003)

Phenolic compounds can be nitrated by 65% nitric acid in the presence of catalytic amounts of montmorillonite KSF and bismuth(III) nitrate to give the corresponding nitrated products in good yields in a heterogeneous phase. The co-catalyst of KSF and Bi(NO3)3 can be easily recovered and reused in the next batch of nitration.

Cloning and comparison of third β-glucoside utilization (bglEFIA) operon with two operons of Pectobacterium carotovorum subsp. carotovorum LY34

Hong, Su Young,An, Chang Long,Cho, Kye Man,Lee, Sun Mi,Kim, Yong Hee,Kim, Min Keun,Cho, Soo Jeong,Lim, Yong Pyo,Kim, Hoon,Yun, Han Dae

, p. 798 - 807 (2006)

A third bgl operon containing bglE, bglF, bglI, and bglA was isolated from Pectobacterium carotovorum subsp. carotovorum LY34 (Pcc LY34). The sequences of BglE, BglF, and Bgll were similar to those of the phosphotransferase system (PTS) components IIB, II

A copper nitride catalyst for the efficient hydroxylation of aryl halides under ligand-free conditions

Mitsudome, Takato,Mizugaki, Tomoo,Xu, Hang,Yamaguchi, Sho

, p. 6593 - 6597 (2021)

Copper nitride (Cu3N) was used as a heterogeneous catalyst for the hydroxylation of aryl halides under ligand-free conditions. The cubic Cu3N nanoparticles showed high catalytic activity, comparable to those of conventional Cu catalysts with nitrogen ligands, demonstrating that the nitrogen atoms in Cu3N act as functional ligands that promote hydroxylation.

New mixed ligand cobalt(II/III) complexes based on the drug sodium valproate and bioactive nitrogen-donor ligands. Synthesis, structure and biological properties

Abu Ali, Hijazi,Abu Shamma, Amani,Kamel, Shayma

, p. 40 - 47 (2017)

New cobalt valproate complexes with different nitrogen based ligands were synthesized and characterized using various techniques such as IR, UV–Vis, single crystal X-ray diffraction as well as other physical properties. The general formula of the prepared

Coaxial electrospun fibermat of poly(AM/DAAM)/ADH and PCL: Versatile platform for functioning active enzymes

Ando, Ren,Ido, Yuya,Kasuga, Toshihiro,Mizuno, Toshihisa,Nagata, Kenji,Obata, Akiko,Tanikawa, Yuji

, p. 1155 - 1163 (2020)

In this study, we prepared and characterized enzyme (αchymotrypsin or lactase)-encapsulating core-shell fibermats by electrospinning. The hydrophilic copolymer of acrylamide (AM) and diacetone acrylamide (DAAM), poly(AM/DAAM), was used as the base materia

Isomer Distribution Ratios of Phenols in Aromatic Hydroxylation with the Hydroxy Radical Generated from α-Azohydroperoxide in Anhydrous Organic Media. Comparison with Fenton's Reagent

Tezuka, Takahiro,Narita, Nozomu,Ando, Wataru,Oae, Shigeru

, p. 3045 - 3049 (1981)

New isomer distribution ratios of phenols in aromatic hydroxylation with the hydroxyl radical generated from α-azohydroperoxide (1) in anhydrous organic media are reported.Photodecomposition of 1 (10-2 M) in anisole, toluene, chlorobenzene, and nitrobenzene under argon or oxygen gas gave methoxyphenol, cresol, chlorophenol, and nitrophenol, respectively, in yield and isomer ratios listed in Table I.Photodecomposition of 1 (10-2 M) in acetonitrile containing toluene or nitrobenzene with various molar ratios under argon gas or under degassed conditions revealed that the isomer ratios under argon gas presented in Table I were reproducible as long as the reactions were conducted in an excess of the substrate.On the other hand, isomer ratios were varied when the reactions were carried out in an excess of 1 compared with the amount of substrate.The isomer ratios were also varied when oxygen was present in the reactants.On the basis of the isomer ratios found by this study, the degree of electrophilicity of the hydroxyl radical generated from 1 under anhydrous conditions and the mechanism of the aromatic hydroxylation are discussed in comparison with the aromatic hydroxylation with Fenton's reagent and others and with the aromatic phenylation, methylation, and trimethylsilylation reported in the literature.

Metalloglycosidase Mimics: Oxidative Cleavage of Saccharides Promoted by Multinuclear Copper Complexes under Physiological Conditions

Yu, Zhen,Thompson, Zechariah,Behnke, Shelby L.,Fenk, Kevin D.,Huang, Derrick,Shafaat, Hannah S.,Cowan

, p. 11218 - 11222 (2020)

Degradation of saccharides is relevant to the design of catalytic therapeutics, the production of biofuels, inhibition of biofilms, as well as other applications in chemical biology. Herein, we report the design of multinuclear Cu complexes that enable cl

A Bioorthogonal Reaction of N-Oxide and Boron Reagents

Kim, Justin,Bertozzi, Carolyn R.

, p. 15777 - 15781 (2015)

The development of bioorthogonal reactions has classically focused on bond-forming ligation reactions. In this report, we seek to expand the functional repertoire of such transformations by introducing a new bond-cleaving reaction between N-oxide and boron reagents. The reaction features a large dynamic range of reactivity, showcasing second-order rate constants as high as 2.3×103 M-1 s-1 using diboron reaction partners. Diboron reagents display minimal cell toxicity at millimolar concentrations, penetrate cell membranes, and effectively reduce N-oxides inside mammalian cells. This new bioorthogonal process based on miniscule components is thus well-suited for activating molecules within cells under chemical control. Furthermore, we demonstrate that the metabolic diversity of nature enables the use of naturally occurring functional groups that display inherent biocompatibility alongside abiotic components for organism-specific applications. The bond-cleaving reaction between N-oxide and diboron reagents features second-order rate constants as high as 2.3×103 M-1 s-1. Diboron reagents display minimal cell toxicity at millimolar concentrations, penetrate cell membranes, and reduce N-oxides inside mammalian cells. This new bioorthogonal reaction is thus well-suited for chemically activating molecules within cells.

Origin of rate-acceleration in ester hydrolysis with metalloprotease mimics

Kim, Dong H.,Lee, Soo Suk

, p. 647 - 652 (2000)

Mimics of carboxypeptidase A, a prototypical metalloprotease, were synthesized by linking macrocyclicpolyamines to the primary side of β-cyclodextrin followed by complexing with Zn(II). These enzyme mimics exhibit saturation kinetics in hydrolysis of p-ni

Synthesis of new Cu(II)-chelating ligand amphiphiles and their esterolytic properties in cationic micelles

Bhattacharya, Santanu,Snehalatha, Karnam,Kumar, V. Praveen

, p. 2741 - 2747 (2003)

Four new tetradentate 2,6-disubstituted pyridine and tridentate 2-substituted pyridine ligands were synthesized. Two of these compounds possessed a metal ion binding subunit in the form of a 2,6-disubstituted-4-N,N′-dimethylamine pyridine moiety. Cu2+-complexes of these ligands incorporated in cetyltrimethylammonium bromide (CTABr) micelles speeded the cleavage of p-nitrophenyldiphenyl phosphate and p-nitrophenyl hexanoate at pH 7.6. On the basis of a kinetic version of Job plot analysis, a 1:1 ligand/Cu2+ stoichiometry was found to be the most active species. In CTABr micelles, the pKa values for the Cu2+-coordinated hydroxyl or pendant-CH2OH in these ligands were between 7.8 and 7.9. The metallomicellar systems displayed catalytic (turnover) behavior in the presence of excess substrates.

Scalable and Template-Free Aqueous Synthesis of Zirconium-Based Metal-Organic Framework Coating on Textile Fiber

Ma, Kaikai,Islamoglu, Timur,Chen, Zhijie,Li, Peng,Wasson, Megan C.,Chen, Yongwei,Wang, Yuanfeng,Peterson, Gregory W.,Xin, John H.,Farha, Omar K.

, p. 15626 - 15633 (2019)

Organophosphonate-based nerve agents, such as VX, Sarin (GB), and Soman (GD), are among the most toxic chemicals to humankind. Recently, we have shown that Zr-based metal-organic frameworks (Zr-MOFs) can effectively catalyze the hydrolysis of these toxic chemicals for diminishing their toxicity. On the other hand, utilizing these materials in powder form is not practical, and developing scalable and economical processes for integrating these materials onto fibers is crucial for protective gear. Herein, we report a scalable, template-free, and aqueous solution-based synthesis strategy for the production of Zr-MOF-coated textiles. Among all MOF/fiber composites reported to date, the MOF-808/polyester fibers exhibit the highest rates of nerve agent hydrolysis. Moreover, such highly porous fiber composites display significantly higher protection time compared to that of its parent fabric for a mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES). A decreased diffusion rate of toxic chemicals through the MOF layer can provide time needed for the destruction of the harmful species.

Synthesis of cyclic oligomers from histidine-derived building blocks using dynamic combinatorial chemistry

Matsumoto, Masaomi,Nicholas, Kenneth M.

, p. 9308 - 9313 (2007)

(Chemical Equation Presented) Histidine-derived hydrazide acetal monomers (3-dimethoxymethylbenzoyl)-L-histidine methyl ester 1 and (3- dimethoxymethylbenzoyl)-τ-benzyl-L-histidine methyl ester 2 were prepared from a histidine methyl ester and a τ-benzyl-

Solvent-free one-step photochemical hydroxylation of benzene derivatives by the singlet excited state of 2,3-dichloro-5,6-dicyano-p-benzoquinone acting as a super oxidant

Ohkubo, Kei,Hirose, Kensaku,Fukuzumi, Shunichi

, p. 2855 - 2861 (2015)

Photoinduced hydroxylation of neat deaerated benzene to phenol occurred under visible-light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), which acts as a super photooxidant in the presence of water. Photocatalytic solvent-free hydroxylation of benzene derivatives with electron-withdrawing substituents such as benzonitrile, nitrobenzene, and trifluoromethylbenzene used as neat solvents has been achieved for the first time by using DDQ as a super photooxidant to yield the corresponding phenol derivatives and 2,3-dichloro-5,6-dicyanohydroquinone (DDQH2) in the presence of water under deaerated conditions. In the presence of dioxygen and tert-butyl nitrite, the photocatalytic hydroxylation of neat benzene occurred with DDQ as a photocatalyst to produce phenol. The photocatalytic reactions are initiated by oxidation of benzene derivatives with the singlet and triplet excited states of DDQ to form the corresponding radical cations, which associate with benzene derivatives to produce the dimer radical cations, which were detected by the femto- and nanosecond laser flash photolysis measurements to clarify the photocatalytic reaction mechanisms. Radical cations of benzene derivatives react with water to yield the OH-adduct radicals. On the other hand, DDQC?- produced by the photoinduced electron transfer from benzene derivatives reacts with the OH-adduct radicals to yield the corresponding phenol derivatives and DDQH2. DDQ is recovered by the reaction of DDQH2 with tert-butyl nitrite when DDQ acts as a photocatalyst for the hydroxylation of benzene derivatives by dioxygen.

Purification and characterization of a novel pyrethroid hydrolase from Aspergillus niger ZD11

Liang, Wei Q.,Wang, Zhuo Y.,Li, He,Wu, Pei C.,Hu, Ji M.,Luo, Na,Cao, Li X.,Liu, Yu H.

, p. 7415 - 7420 (2005)

The pyrethroid pesticides residues on foods and environmental contamination are a public safety concern. Pretreatment with pyrethroid hydrolase has the potential to alleviate the conditions. For this purpose, a fungus capable of using pyrethroid pesticides as a sole carbon source was isolated from the soil and characterized as Aspergillus niger ZD11. A novel pyrethroid hydrolase from cell extract was purified 41.5-fold to apparent homogeneity with 12.6% overall recovery. It is a monomeric structure with a molecular mass of 56 kDa, a pl of 5.4, and the enzyme activity was optimal at 45°C and pH 6.5. The activities were strongly inhibited by Hg2+, Ag+, and p-chloromercuribenzoate, whereas less pronounced effects (5-10% inhibition) were observed in the presence of the remaining divalent cations, the chelating agent EDTA and phenanthroline. The purified enzyme hydrolyzed various insecticides with similar carboxylester. trans-Permethrin is the preferred substrate.

Effects of cyclodextrin on hydrolysis and the Smiles rearrangement of salicylic acid esters

Yatsimirsky,Bezsoudnova

, p. 2517 - 2524 (1996)

The effect of β-cyclodextrin (β-CD) on "aqueous" hydrolysis of methyl, p-, and m-nitrophenyl salicylates as well as on the Smiles rearrangement of p-nitrophenyl salicylate was studied. No effect of β-CD on the pH-independent rate constant of "aqueous" hydrolysis of methyl ester was observed, while β-CD accelerated "aqueous" hydrolysis of nitrophenyl esters by ca. 10 times. The inclusion of these esters into the cavity of β-CD is accompanied by a change in the mechanism of hydrolysis: free ester in the deprotonated form undergoes hydrolysis through the mechanism of intramolecular general base catalysis, while the ester bound to cyclodextrin is hydrolyzed due to the nucleophilic attack of the deprotonated hydroxyl group of β-CD at a neutral substrate molecule. The effects of cyclodextrin on the rate constant of borate-catalyzed hydrolysis were interpreted by assuming that the substrate bound to β-CD undergoes borate-assisted attack at the deprotonated cyclodextrin hydroxyl group. The Smiles rearrangement, which is an intramolecular nucleophilic substitution reaction, is accelerated in the presence of β-CD.

Molecular basis of perhydrolase activity in serine hydrolases

Bernhardt, Peter,Hult, Karl,Kazlauskas, Romas J.

, p. 2742 - 2746 (2005)

(Chemical Equation Presented) Changing substrates: A mutation that forms a cis-proline-peptide bond in a loop structure close to the active site of an aryl esterase from Pseudomonas fluorescens converts the enzyme into a perhydrolase (see picture). The sw

A novel organic-solvent and detergent resistant esterase from Bacillus sp. isolated from Bazangan Lake

Pasban-Ziyarat, Fatemeh,Mehrzad, Jamshid,Asoodeh, Ahmad,Deiminiat, Behjat,Motavalizadehkakhky, Alireza

, (2021)

This study reports biochemical features of a novel esterase of Bacillus sp. HP 96 isolated from Bazangan Lake in Iran. The optimum pH and temperature for 53.4 kDa-purified esterase were 8 and 40 °C, respectively. The HPLC technique was used to examine the

Carbonate-bridged dinuclear lanthanide(III) complexes of chiral macrocycle

Gerus, Aleksandra,?lepokura, Katarzyna,Lisowski, Jerzy

, p. 115 - 121 (2019)

Mononuclear Eu(III) and Dy(III) complexes of the chiral hexaaza macrocycle L, 2(R),7(R),18(R),23(R)-1,8,15,17,24,31-hexaazatricyclo[25.3.1.1.0.0]-dotriaconta-10,12,14,26,28,30-hexaene have been obtained as chloride derivatives (1 and 2, respectively) and

New Tricks for Old Proteins: Single Mutations in a Nonenzymatic Protein Give Rise to Various Enzymatic Activities

Moroz, Yurii S.,Dunston, Tiffany T.,Makhlynets, Olga V.,Moroz, Olesia V.,Wu, Yibing,Yoon, Jennifer H.,Olsen, Alissa B.,McLaughlin, Jaclyn M.,Mack, Korrie L.,Gosavi, Pallavi M.,Van Nuland, Nico A. J.,Korendovych, Ivan V.

, p. 14905 - 14911 (2015)

Design of a new catalytic function in proteins, apart from its inherent practical value, is important for fundamental understanding of enzymatic activity. Using a computationally inexpensive, minimalistic approach that focuses on introducing a single high

Catalysis of Aromatic Nitration by the Lower Oxides of Nitrogen

Ross, David S.,Hum, Georgina P.,Blucher, William G.

, p. 532 - 533 (1980)

In the absence of nitrous acid traps, the nitration of phenol in 56.2percent sulphuric acid displays autocatalytic behaviour; on the other hand, the isomer ratio of the products is inconsistent with the commonly accepted prior nitrosation scheme, and some other route for the promotion of nitration must be operative.

Cloning, expression, and characterization of a thermostable PAP2L2, a new member of the type-2 phosphatidic acid phosphatase family from Geobacillus toebii T-85

Zhang, Yong,Yang, Zhenxing,Huang, Xiaodong,Peng, Jing,Fei, Xiangwei,Gu, Shaohua,Xie, Yi,Ji, Chaoneng,Mao, Yumin

, p. 3134 - 3141 (2008)

Most members of the type-2 phosphatidic acid phosphatase (PAP2) superfamily are integral membrane phophatases involved in lipid-related signal transduction and metabolism. Here we describe the cloning of a novel gene from Geobacillus toebii T-85, encoding

Purification and characterization of lipase from Spirulina platensis

Demir, Burcu Saygideger,Tuekel, S. Seyhan

, p. 123 - 128 (2010)

A lipase from photosynthetic cyanobacterium Spirulina platensis (Arthrospira) was purified by sequential operation of ammonium sulphate precipitation, dialysis, DEAE-Sepharose anion exchange chromatography, and Sepharose-6B gel filtration chromatography f

Linear free energy relationships of the inhibition of pancreatic cholesterol esterase by 4-nitrophenyl-N-alkylcarbamate

Lin, Gialih,Lai, Cheng-Yue

, p. 193 - 196 (1996)

4-Nitrophenyl-N-alkylcarbamates (1) as active site-directed irreversible inhibitors of pancreatic cholesterol esterase are investigated for values of the dissociation constant (K(i)), the carbamylation constant (k2), and the bimolecular rate co

Differential expression of nucleotide pyrophosphatase/phosphodiesterases by Walker 256 mammary cancer cells in solid tumors and malignant ascites

Buffon, Andréia,Casali, Emerson A.,Cardoso, Valesca V.,Zerbini, Luiz F.,Robson, Simon C.,Sarkis, Jo?o J.F.,Wink, Márcia R.

, p. 435 - 440 (2010)

Aims: Expression of ectoenzymes responsible for nucleotide phosphohydrolysis to form adenosine may represent a mechanism that facilitates the proliferation and spread of malignancy. In this study, we have identified and characterized the ectonucleotide py

Enzyme immunoassay for phenobarbital

Aoki,Terasawa,Kuriowa

, p. 3291 - 3295 (1980)

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Enzymatic properties and transglycosylation of α-galactosidase from Penicillium oxalicum so

Kurakake, Masahiro,Moriyama, Youichirou,Sunouchi, Riku,Nakatani, Shinya

, p. 177 - 182 (2011)

Penicillium oxalicum SO α-galactosidase demonstrated weak hydrolysing activity but a high rate of transglycosylation in the reaction with melibiose, where the major product was 6-α-galactosyl melibiose. The transfer ratio was 83.6% and was maintained over

Nucleophilic displacement on 4-nitrophenyl dimethyl phosphinate by ethoxide ion: Alkali metal ion catalysis and mechanism

Buncel, Erwin,Albright, Kendall G.,Onyido, Ikenna

, p. 601 - 610 (2004)

We report on a spectrophotometric kinetic study of the effect of Li + and K- cations on the ethanolysis of 4-nitrophenyl dimethylphosphinate (4a) in ethanol at 25°C. The nucleophilic displacement reaction of 4a with LiOEt and KOEt in the absence and presence of 18-crown-6 ether (18-C-6) furnished observed first-order rate constants which increase in the order EtO-MOEt. Derived δG ip, δGts and ΔGcat values quantify ground state and transition state stabilization by the metal ions to give δGtn>δGip for Li+ and δGts~δGip for K+. These results indicate moderate catalysis by Li+, with 4a manifesting lesser susceptibility to catalysis than other substrates previously studied. Second-order rate constants for the reaction of the aryl dimethylphosphinates 4a-f with free EtO- were obtained from plots of log kobs vs. [KOEt], measured in the presence of excess 18-C-6. Hammett plots with σ and σ° substituent constants give significantly better correlation of rates than σ- and yield a moderately large ρ(ρ°) value; this is interpreted in terms of a stepwise mechanism involving rate-limiting formation of a pentacoordinate intermediate. Comparison of the present results with those of Williams on the aqueous alkaline hydrolysis of Me2P(O)-OPhX and Ph2P(O)-OPhX esters, establishes the rationale for a change in mechanism in the more basic EtO/EtOH nucleophile/solvent system by a stepwise mechanism instead of a concerted one in aqueous base. Structure-reactivity correlations following Jencks show that the change in mechanism is accounted for by cross interactions between the nucleophile and the leaving group in the transition state. The observed duality of mechanism is rationalized on the basis of the More O'Ferrall-Jencks diagram, as a spectrum of transition states covering a wide range of nucleophile and leaving group basicities.

Stille couplings with fluorous tin reactants: Attractive features for preparative organic synthesis and liquid-phase combinatorial synthesis

Curran, Dennis P.,Hoshino, Masahide

, p. 6480 - 6481 (1996)

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Versatile catalysis of “natural extract”: oxidation of sulfides and alcohols and ipso-hydroxylation of arylboronic acids

Dutta, Apurba,Ali, Abdul Aziz,Sarma, Diganta

, p. 2379 - 2388 (2019)

Abstract: In the present work, we have described the versatile applications of naturally available inexpensive citrous lemon juice as biocatalyst for controlled oxidation of sulfides and alcohols and ipso-hydroxylation of arylboronic acids using 30% H2O2 as a green oxidant. A series of structurally divergent sulfides and benzyl alcohols were oxidized to their corresponding sulfoxides and aldehydes, respectively, with good-to-excellent yields. Similarly, aryl and heteroaryl boronic acids were rapidly, often within minutes, transformed to their corresponding phenols at room temperature. Graphic abstract: [Figure not available: see fulltext.]

D-Glucose as green ligand for selective copper-catalyzed phenol synthesis from aryl halides with an easy catalyst removal

Thakur, Krishna Gopal,Sekar, Govindasamy

, p. 6692 - 6694 (2011)

With the growing demand of environmentally friendly reagents for organic reactions, for the first time the utility of d-glucose as a ligand in its direct form has been described using a typical example of copper-catalyzed coupling reaction for phenol synthesis with a high degree of selectivity and easy catalyst removal.

Highly stabilized lipase in polyaniline nanofibers for surfactant-mediated esterification of ibuprofen

Hong, Sung-Gil,Kim, Han Sol,Kim, Jungbae

, p. 911 - 915 (2014)

Lipase (LP) from Candida rugosa was immobilized and stabilized in polyaniline nanofibers (PANFs) via a three-step process of enzyme adsorption, precipitation, and cross-linking, which generates the final immobilization called "EAPC". The activity of EAPC

Heterogeneous copper-catalyzed hydroxylation of aryl iodides under air conditions

Ding, Guodong,Han, Hongling,Jiang, Tao,Wu, Tianbin,Han, Buxing

, p. 9072 - 9075 (2014)

In this work, the ligand-free heterogeneous copper Cu-g-C3N 4 was synthesized and used for the hydroxylation of aryl iodides to synthesize phenols using cheap bases. The catalyst was conveniently prepared, air-tolerant, reusable and scalable, and is very efficient for a wide range of substrates. The synthesis of substituted phenols can be carried out under air conditions and has great potential for practical applications. This journal is the Partner Organisations 2014.

Selective hydroxylation of aryl iodides to produce phenols under mild conditions using a supported copper catalyst

Auni, Anika,Ding, Guodong,Hao, Leiduan,Li, Tao,Li, Xiaoyu,Xu, Haiping,Zhang, Qiang

, p. 25348 - 25353 (2021)

Owing to the high activity and low-cost, copper-based catalysts are promising candidates for transforming aromatic halides to yield phenols. In this work, we report the selective hydroxylation of aromatic iodides to produce phenols using an atomically dispersed copper catalyst (Cu-ZnO-ZrO2) under mild reaction conditions. The reactions were conducted without the use of additional organic ligands, and the protection of an inert atmosphere environment is not required. The catalyst can be easily prepared, scalable, and is very efficient for a wide range of substrates. The catalytic reactions can be carried out with only 1.24 mol% Cu loading, which shows great potential in mass production.

Enhancement of active compound, genipin, from Gardeniae Fructus using immobilized glycosyl hydrolase family 3 β-glucosidase from Lactobacillus antri

Kim, Young Soo,Lee, Chung-Jo,Ma, Jin Yeul

, (2017)

Geniposide is an iridoid glycoside, which is abundant in Gardeniae Fructus. Despite the various pharmaceutical effects of geniposide on a human body, its hydrolysis into a smaller molecule, genipin, by β-glucosidase produced by bacteria in the intestines is particularly important to improve geniposide uptake into the body. Since geniposide is much more abundant in Gardeniae Fructus than its aglycone genipin, we herein transformed geniposide into genipin using purified recombinant β-glucosidase from Lactobacillus antri (rBGLa), which was expressed in Escherichia coli to enhance the genipin content. Purified rBGLa was characterized using p-nitrophenyl β-d-glucopyranoside, and the optimal temperature and pH for its β-glucosidase activity were found to be 45?°C and 6.0. When the enzyme was immobilized, rBGLa was active at higher temperatures than the free enzyme, and we confirmed that its stability upon changes in pH and temperature was highly improved. Using 0.5?μg/mL free rBGLa, single compound of 0.4?mM geniposide was efficiently converted into genipin within 2?h, and the immobilized rBGLa also successfully transformed geniposide in a hot-water extract of Gardeniae Fructus into the aglycone, which makes it applicable to the food and pharmaceutical industries.

Polyoxomolybdate promoted hydrolysis of a DNA-model phosphoester studied by NMR and EXAFS spectroscopy

Absillis, Gregory,Van Deun, Rik,Parac-Vogt, Tatjana N.

, p. 11552 - 11560 (2011)

Hydrolysis of (p-nitrophenyl)phosphate (NPP), a commonly used phosphatase model substrate, was examined in molybdate solutions by means of 1H, 31P, and 95Mo NMR spectroscopy and Mo K-edge Extended X-ray Absorption Fine Str

OXIDATION OF NITROBENZENES BY OXYGEN IN A KOH-ORGANIC SOLVENT-18-CROWN-6 ETHER SYSTEM

Grinfel'd, A. A.,Artamkina, G. A.,Beletskaya, I. P.

, p. 2332 (1982)

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Cucurbit[7]uril/CuCl promoting decomposition of 4-nitrobenzenediazonium in aqueous solution

Xu, Hongxing,Wang, Qiaochun

, p. 337 - 339 (2019)

4-Nitro-benzendiazonium (4-NBD) was found to form a 1:1 host-guest complex (NBD@CB) with cucurbit[7]uril (CB[7]) in aqueous solution and 4-NBD enters into the cavity of CB[7] with a binding constant of 1.28 × 105 L/mol. NBD@CB can be decomposed into a nitrobenzene/4-nitrophenol mixture in a high total yield (61% + 33%) in the presence of CuCl, unlike the decomposition of 4-NBD in the presence of either CB[7] or CuCl, or both absence, where would result in significant amounts of unknown byproducts. This work might provide an economic and effective way to obtain arenes or phenols through the substitution of diazonium salts.

Tuning the intramolecular charge transfer (ICT) process in push-pull systems: Effect of nitro groups

Panja, Sumit Kumar,Dwivedi, Nidhi,Saha, Satyen

, p. 105786 - 105794 (2016)

The intramolecular charge transfer (ICT) process in donor-acceptor systems has tremendous importance in various physical and biological systems. Three nitrophenolate salts were synthesized and studied here. The ICT and π → π? transition processes were identified in these derivatives using UV-Vis spectroscopy and theoretical calculations. It was observed that by simple substitution with nitro groups, one can generate and control the ICT process by regulating the charge distribution over the molecule. While for a monosubstitute nitro derivative, only one ICT band was observed, additional ICT processes can be generated at will by introducing a second nitro group. The intensity of this second ICT channel can be regulated with introduction of a third nitro group. Further, the association constants and solvation processes for these potassium nitrophenolate derivatives were found to be drastically dependent on the number of ICT channels present in the molecule. Theoretical studies (MEP analysis) support the experimental observations presented here. The results show that by simply introducing additional acceptor groups to the system, one can tune the ICT band efficiently in a conjugate system.

Three-coordinate copper(I) 2-hydroxy-1,10-phenanthroline dinuclear complex catalyzed homocoupling of arylboronic acids towards biphenyls under air condition

Wang, Yan-Hong,Xu, Mei-Chen,Liu, Jie,Zhang, Ling-Juan,Zhang, Xian-Ming

, p. 9598 - 9601 (2015)

An efficient synthesis of biphenyls via three-coordinate planar dinuclear Cu2(ophen)2 complex catalyzed homocoupling of arylboronic acids under air condition and in the condition of alkali-free was demonstrated. Uniquely, this catalyst shows high selectivity towards biphenyls when the reaction was conducted in aqueous solution, which is significantly different from selectivity towards phenols in related Cu-catalysts. Utilization of environmentally friendly water as main solvent, reaction at room temperature and in the absence of base, cheapness, low loading and easy bulk preparation of catalyst make it potential in green synthesis of biphenyls.

Unravelling the role of ultrasonic energy in the enhancement of enzymatic kinetics

Galesio,Loureno,Madeira,Diniz,Capelo

, p. 9 - 15 (2012)

The enzymatic hydrolysis of anabolic androgenic steroids excreted to urine as glucuronide conjugates has been recently reported to be improved by applying ultrasonic energy to the reaction medium. The hydrolysis time using β-glucuronidase from Escherichia coli K12 was reduced by a factor of six when ultrasonic energy was employed to enhance the enzymatic kinetic. In this study, the effect of ultrasonic energy on the enzymatic hydrolysis kinetic parameters, as well as on the enzymatic activity of β-glucuronidase from E. coli K12 was assessed. The study was conducted using the compounds 4-nitrophenyl-β-d-glucuronide and 4-nitrophenol. Experimental data suggested that the reaction follows the Michaelis-Menten kinetics type. In addition it was found that the ultrasonic energy affects the initial velocity of reaction, which is higher when ultrasound waves are employed when compared to the classical method of incubation at 55 °C. Moreover the values of V max and kcat are higher for the ultrasonic essay (V max(US) = 17.1 ± 0.8 μM min-1; k cat(US) = 340,523 min-1; Vmax(55 °C) = 14.8 ± 0.7 μM min-1; kcat(55 °C) = 295,187 min-1) whilst the Michaelis-Menten constant obtained for the two methodologies showed similar values (KM(US) = 94.7 ± 7.2 μM; KM(55 °C) = 92.5 ± 6.6 μM). Deactivation of the enzyme was also observed under ultrasonic energy, which was found particularly evident for experimental conditions with excess of substrate; enzymatic activity half-life time increased with the increase of the E/S ratio. This research work seems to support the idea that the use of ultrasonic energy affects the transition state of the enzymatic reaction and that mass transfer processes are also most likely enhanced. .

-

Zabik,Schuetz

, p. 300,301 (1967)

-

Amine-functionalized magnetic nanocomposite particles for efficient immobilization of lipase: effects of functional molecule size on properties of the immobilized lipase

Esmaeilnejad-Ahranjani, Parvaneh,Kazemeini, Mohammad,Singh, Gurvinder,Arpanaei, Ayyoob

, p. 33313 - 33327 (2015)

A cost-effective design of reusable enzyme-functionalized particles with better catalytic activity is of great scientific interest due to their applications in a wide range of catalytic reactions in several industrial processes. In this work, a systematic

Photochemical Nucleophilic Substitution Reactions of Methyl Substituted Derivatives of p- and o-Nitroanisole

Sawaura, Masaki,Mukai, Toshio

, p. 3213 - 3214 (1981)

Photosubstitution reactions of several methyl substituted derivatives of p- and o-nitroanisole with hydroxide ion were investigated.The methyl substituent seemed to show an uncertain (probably electronic) effect in addition to the steric effect for the replacement of both the methoxy and the nitro groups.Mainly, the replacement reaction of the nitro group is discussed.

THE SYNTHESIS OF AN ACTIVE DERIVATIVE OF CYCLOMALTOHEPTAOSE FOR THE HYDROLYSIS OF ESTERS AND THE FORMATION OF AMIDE BONDS

Ekberg, Bjoern,Andersson, Lars I.,Mosbach, Klaus

, p. 111 - 118 (1989)

The synthesis is described of a derivative of cyclomaltoheptaose (β-cyclodextrin) to which the tripeptide Ser-His-Asp, the catalytic triad found in chymotrypsin, has been coupled.The derivative enhanced the rates of hydrolysis of activated esters, as meas

Comparison of three thermostable β-glucosidases for application in the hydrolysis of soybean isoflavone glycosides

Song, Xiangfei,Xue, Yemin,Wang, Qilei,Wu, Xixi

, p. 1954 - 1961 (2011)

A novel thermostable β-glucosidase (Te-BglA) from Thermoanaerobacter ethanolicus JW200 was cloned, characterized and compared for its activity against isoflavone glycosides with two β-glucosidases (Tm-BglA, Tm-BglB) from Thermotoga maritima. Te-BglA exhib

Properties of a metagenome-derived β-glucosidase from the contents of rabbit cecum

Feng, Yi,Duan, Cheng-Jie,Liu, Li,Tang, Ji-Liang,Feng, Jia-Xun

, p. 1470 - 1473 (2009)

In this study, a previously cloned β-glucosidase gene, umbgl3B, was heterologously expressed in Escherichia coli, and the biochemical properties of the purified enzyme were characterized. The recombinant enzyme was stable over a wide range of pH values (5.0-9.0) and below 30 °C. It displayed optimum enzymatic activity at pH 6.5 at 40 °C, under condition similar to that in the rabbit cecum, suggesting an active role of the native enzyme in vivo. The recombinant β-glucosidase Umbgl3B showed high activity to aryl β-D-glucosides and low activity to cellooligosaccharides, with a polymerization degree of less than 5. The enzyme had no activity toward long cellooligosaccharides or polysaccharides. The aspartic acid residue, D772, of the wildtype Umbgl3B was predicted as a nucleophile. Mutant D772A was constructed. It showed less than 1/10, 000 activity of the wild-type enzyme, but had the same properties, suggesting that residue D772 plays a key role in the enzyme's activity.

Preparation of salidroside with n-butyl β-D-glucoside as the glycone donor via a two-step enzymatic synthesis catalyzed by immobilized β-glucosidase from bitter almonds

Wang, Feng,Huang, Dengfa,Ma, Yong,Zhang, Fuming,Linhardt, Robert J.

, p. 246 - 260 (2019)

β-Glucosidase from bitter almonds was immobilized on epoxy group-functionalized beads for catalyzing salidroside synthesis in a two-step process with n-butyl-β-D-glucoside (BG) as the glucosyl donor. The formation of salidroside ((0.59 ± 0.02) M) at a yield of 39.04%±1.25% was accomplished in 8 h by the transglucosylation of immobilized β-glucosidase at pH?8.0 and 50 °C when the ratio of BG to tyrosol was 1:2 (mol/mol). A study on the influence of different glycosyl acceptors demonstrated that the yield of the glucosylation reaction of phenylmethanol and cyclohexanol was higher than that of either phenol or cyclohexanol. This may account for the selectivity of the immobilized enzyme towards the alcoholic hydroxyl group of tyrosol in the salidroside synthesis reaction. A study on the synthesis of BG via the reverse hydrolysis of immobilized β-glucosidase showed that a yield of 78.04%±2.2% BG can be obtained with a product concentration of (0.23 ± 0.015) M.

Protection of alcohols and phenols with dihydropyran and detetrahydropyranylation by ZrCl4

Rezai, Nasrin,Meybodi, Farhat Alsadat,Salehi, Peyman

, p. 1799 - 1805 (2000)

Alcohols and Phenols are protected efficiently with dihydropyran(DHP) in the presence of catalytic amounts of zirconium tetrachloridein dichloromethane. Deprotection of THP-ethers is also afforded in a methanolic solution at room temperature.

Regioselectivity of the nitration of phenol by acetyl nitrate adsorbed on silica gel

Augusto,Rodrigues,De Oliveira Filho, Antonio Pedro,Moran, Paulo J. S.,Custodio, Rogerio

, p. 6733 - 6738 (1999)

The reaction of phenol with acetyl nitrate in chloroform gives nitrophenol with an ortho/para ratio of 1.8. This ratio increase to 13.3 when the reaction was carried out with acetyl nitrate pre-adsorbed on dry silica gel. Silica may be acting as a template to bring phenol close to acetyl nitrate by hydrogen bonds forming a ternary complex, which undergoes a six- center rearrangement to o-nitrophenol. The formation of this ternary complex is evaluated by ab initio molecular orbital calculation.

Modification of an Enzyme Biocatalyst for the Efficient and Selective Oxidative Demethylation of para-Substituted Benzene Derivatives

Chao, Rebecca R.,Lau, Ian C.-K.,De Voss, James J.,Bell, Stephen G.

, p. 3626 - 3635 (2016)

The bacterial CYP199A4 enzyme is able to oxidise a narrow range of aromatic acids, which includes 4-methoxybenzoic acid, efficiently. A serine 244 to aspartate variant was identified with enhanced activity for a wide range of para-methoxy-substituted benzenes. Substrates in which the acidic benzoic acid moiety is replaced with a phenol and the amide, aldehyde and bromide analogues were all oxidised with high activity by the S244D mutant (product formation rate >600 nmol nmolCYP ?1 min?1) with turnover numbers of up to 20 000. If the carboxylate moiety was modified to a nitro, ketone, boronic acid, hydroxymethyl or nitrile group, these substrates were also oxidised at a significantly higher activity by S244D than the wild-type enzyme. 3,4-Dimethoxybenzaldehyde was demethylated selectively and oxidatively to 3-methoxy-4-hydroxybenzaldehyde by the S244D mutant 84-fold more rapidly than with the wild-type enzyme. CYP199A4 would have applications in the catalytic regioselective oxidative demethylation of suitably substituted benzene substrates under mild conditions and in the presence of more oxidatively sensitive functional groups, such as an aldehyde.

Reductive deprotection of aryl allyl ethers with Pd(Ph3)4/NaBH4

Beugelmans, Rene,Bourdet, Sebastien,Bigot, Antony,Zhu, Jieping

, p. 4349 - 4350 (1994)

Treatment of aryl allyl ethers with catalytic amounts of Pd(PPh3)4 and NaBH4 at room temperature afforded the parent phenol in high yield under non-hydrolytic conditions.

Chromogenic substrate from 4-nitro-1-naphthol for hydrolytic enzyme of neutral or slightly acidic optimum pH: 4-Nitro-1-naphthyl-β-d- galactopyranoside as an example

Dang, Jizheng,Liu, Hongbo,Yang, Xiaolan,Zhang, Yi,Xie, Yanling,Li, Yuanli,Pu, Jun,Liao, Juan,Yuan, Yonghua,Liao, Fei

, p. 646 - 649 (2013)

At pH from 5.5 to 7.6, absorptivity of 4-nitro-1-naphthol at 450 nm is over 2.1-fold of that of para-nitrophenol at 405 nm and over 9.6-fold of that of ortho-nitrophenol at 415 nm. On 4-nitro-1-naphthyl-β-d-galactopyranoside at pH 7.4, catalytic efficiency of Escherichia coli β-d-galactosidase is 3-fold of that on para-nitrophenyl-β-d-galactopyranoside and about 40% of that on ortho-nitrophenyl-β-d-galactopyranoside, and produces a lower quantification limit of penicillin G by enzyme-linked-immunoabsorbent-assay. Hence, 4-nitro-1-naphthol is favorable to prepare chromogenic substrates of hydrolytic enzymes of neutral or slightly acidic optimum pH.

Evidence That the Effects of Synthetic Amphiphile Vesicles on Reaction Rates Depend on Vesicle Size

Kawamuro, Maria K.,Chaimovich, Hernan,Abuin, Elsa B.,Lissi, E. A.,Cuccovia, Iolanda M.

, p. 1458 - 1463 (1991)

Small and large vesicles were prepared with dioctadecyldimethylammonium chloride and bromide.The hydrodynamic radius of the small vesicles ranges from 11 to 30 nm, while that of the large vesicles is ca. 140 nm.Both small and large vesicles increased the

Hydroxyl radical as a strong electrophilic species

Marusawa, Hiroshi,Ichikawa, Kazuhiko,Narita, Nozomu,Murakami, Hiromu,Ito, Keiichi,Tezuka, Takahiro

, p. 2283 - 2290 (2002)

In order to clarify an index which could be used as proof of the presence of hydroxyl radical, a new standard isomer distribution ratio of phenols formed from aromatic hydroxylation with [(4-bromophenyl)diazenyl](phenyl)methyl hydroperoxide 4, which is a stable source of hydroxyl radical, under a new appropriate photolysis condition in the presence or absence of benzoquinones is reported. We also demonstrated the strong electrophilic properties of hydroxyl radical in reference to earlier results of electron density calculations.

Nitration and hydroxylation of phenolic compounds by peroxynitrite

Ramezanian, Merrikh S.,Padmaja, Sarojini,Koppenol, Willem H.

, p. 232 - 240 (1996)

The kinetics and products of the reaction of peroxynitrite with the phenolic compounds phenol, tyrosine, and salicylate were studied as a function of pH. All reactions are first-order in peroxynitrite and zero- order in the phenolic compound. Relative to

La(III)-hydrogen peroxide cooperativity in phosphate diester cleavage: A mechanistic study

Takasaki, Bryan K.,Chin, Jik

, p. 8582 - 8585 (1995)

La(III), Pr(III), Nd(III), and Eu(III) (2 mM) can each combine with hydrogen peroxide to provide close to 9 orders of magnitude rate acceleration for hydrolyzing BNPP (bis(p-nitrophenyl) phosphate) at pH 7 and 25 °C. The rate of the reaction is second ord

Zirconium and hafnium cations rapidly cleave model phosphodiesters in acidic aqueous solutions

Moss, Robert A.,Zhang, Jing,Ragunathan, Kaliappa G.

, p. 1529 - 1532 (1998)

Aqueous solutions of 20-fold excess Zr4+ and Hf4+ at pH 3.5 (37°C) hydrolyze phosphodiester substrates 1-3 very rapidly. The reactivity of Zr4+ (with rate constants up to 0.015 s-1 for 2 at 1 mM Zr4+)

Reactive-site design in folded-polypeptide catalysts - The leaving group pKa of reactive esters sets the stage for cooperativity in nucleophilic and general-acid catalysis

Nilsson, Jonas,Baltzer, Lars

, p. 2214 - 2220 (2000)

The second-order rate constants for the hydrolysis of nitrophenyl esters catalysed by a number of folded designed polypeptides have been determined, and 1900-fold rate enhancements over those of the 4-methylimidazolecatalysed reactions have been observed. The rate enhancements are much larger than those expected from the pKa depression of the nucleophilic His residues alone. Kinetic solvent isotope effects were observed at pH values lower than the pKa values of the leaving groups and suggests that general-acid catalysis contributes in the pH range where the leaving group is predominantly protonated. In contrast, no isotope effects were observed at pH values above the PKa of the leaving group. A Hammett ρ value of 1.4 has been determined for the peptide-catalysed hydrolysis reaction by variation of the substituents of the leaving phenol. The corresponding values for the imidazole-catalysed reaction is 0.8 and for phenol dissociation is 2.2. There is therefore, very approximately, half a negative charge localised on the phenolate oxygen in the transition state in agreement with the conclusion that transition-state hydrogen-bond formation may contribute to the observed catalysis. The elucidation at a molecular level of the principles that control cooperativity in the biocatalysed ester-hydrolysis reaction represents the first step towards a level of understanding of the concept of cooperativity that may eventually allow us to design tailor-made enzymes for chemical reactions not catalysed by nature.

Enantioselectivity enhancement of ester cleavage by a β-sheet polypeptide containing catalytic triads in a serine protease

Fukushima, Yasumasa

, p. 2269 - 2274 (1996)

Catalytic activity and enantioselectivity of Poly(Asp-Leu-His-Leu-Ser-Leu) with a β-sheet structure for the hydrolysis of chiral phenylalanine p-nitrophenyl esters were compared with those of the peptide hexamer, under various conditions. The relationship

Tertiary Butyl Nitrite Triggered Nitration of Phenols: Solvent- and Structure-Dependent Kinetic Study

Kumar, M. Satish,Rajanna,Venkateswarlu,Rao, K. Lakshman

, p. 171 - 196 (2016)

Nitration of phenols with tertiary butyl nitrite (TBN) obeyed second-order kinetics with a first-order dependence on [TBN] and [phenol] under acid-free conditions. Reaction rates were significantly altered by a change in the dielectric constant and other physical properties of solvent. The rate of nitration increased with an increase in temperature (303-323 K) in different solvent media (acetonitrile, dichloroethane, CCl4, dimethyl formamide (DMF), and toluene). The rates of nitration (log k) could not fit into either Amis or Kirkwood plots [log k' vs. (1/D) or [(D - 1)/(2D + 1)], but the trends were better explained by the basic form of multivariate linear solvent energy relationships (MLSER) suggested by the Koppel and Palm approach on the one hand and the Kamlet and Taft approach on the other hand. These observations probably substantiate that cumulative contributions of basic solvent parameters (equilibrium as well as frictional solvent effects) and solvent-solute interactions for solvation of transition state during nitration of phenols. Reaction rates accelerated with the introduction of electron-donating groups and retarded with electron-withdrawing groups. Accordingly, the reactivity of structurally different phenols was found to follow the following sequence: p-OH > p-MeO > p-Me > H > m-Me > p-Cl > p-Br > m-Cl > p-NO2 > m-OH. The results are interpreted by Hammett's theory of linear free energy relationship. The reaction constant (Hammett's ρ) is a measure of the sensitivity of the reaction toward the electronic effects of the substituent. The rho (ρ) values obtained from the present experiments are fairly large negative values (ρ CH3) versus σ? or, Es or combined Taft's relationship. However, Charton's MLRA of the log k with polar, resonance, steric, hydrophobicity, and molar refractivity showing a very good linear relationship was obtained. It is of interest to note that when log kexp values are correlated with log kcal a perfect linearity is obtained with a correlation coefficient of unity, indicating the consonance between experimental and calculated rate constants in the present work.

PRODUCTION, PURIFICATION, AND PROPERTIES OF AN α-L-ARABINOFURANOSIDASE FROM Dichomitus squalens

Brillouet, Jean-Marc,Moulin, Jean-Claude,Agosin, Eduardo

, p. 113 - 126 (1985)

A white-rot fungus Dichomitus squalens, when grown on 1percent wheat-straw glucuronoarabinoxylan under aerated submerged conditions, secreted an α-L-arabinofuranosidase (4.3 nkat/mL).The enzyme was purified 70-fold by ammonium sulfate precipitation, chrom

Synthesis of a novel prebiotic trisaccharide by a type i α-glucosidase from B. licheniformis strain TH4-2

Nimpiboon, Pitchanan,Nakapong, Santhana,Pichyangkura, Rath,Ito, Kazuo,Pongsawasdi, Piamsook

, p. 448 - 457 (2011)

The use of α-glucosidase from Bacillus licheniformis TH4-2 in the glucosyl transfer reaction for the synthesis of oligosaccharides (OS) was evaluated. The conditions for α-glucosidase production were optimized. The enzyme was 112-fold purified with a 28% yield. The molecular mass was 64 kDa, and the optimum pH and temperature were 6.0 and 45 °C. The highest hydrolytic activity was observed towards p-nitrophenyl α-d-glucopyranoside followed by isomaltose, sucrose and maltose, supporting that it is a type I α-glucosidase. The enzyme could synthesize OS by transglucosylation from sucrose donor using various saccharides as acceptor. Melibiose, an α-galactoside, was selected as an efficient and interesting acceptor. TLC and HPLC analysis of the products revealed that the optimum condition for OS production was pH 6.0 with 15% melibiose, 5% sucrose and 5 U/ml enzyme at 45 °C for 24 h. Under these conditions two product peaks were observed in the HPLC profile with yields of 17.2% and 3.3%. The main product was isolated by Sephadex LH-20 column and analyzed by MS and NMR as the novel 504 Daltons trisaccharide, α-d-glucopyranosyl-(1 → 6)-α-d-galactopyranosyl- (1 → 6)-d-glucopyranose. The prebiotic nature of this product was suggested from its resistance to hydrolysis by rat intestinal acetone powder containing digestible enzymes of rat intestine.

Rapid phosphodiester hydrolysis by zirconium(IV)

Ott, Reina,Kraemer, Roland

, p. 1957 - 1960 (1998)

A 3 x 109-fold faster cleavage of DNA dinucleotide 1 to thymidine and phosphate can be achieved under mild conditions (pH 5.5, 20°C) with a zirconium(IV) complex containing tris(hydroxymethyl)aminomethane as ligand [Eq.(1)]. In view of applications of artificial DNAses to molecular biology and gene therapy, non-redox-active zirconium(IV) is an alternative to the highly efficient but reduction-sensitive cerium(IV).

Cloning and characterization of the β-xylosidase from Dictyoglomus turgidum for high efficient biotransformation of 10-deacetyl-7-xylosltaxol

Li, Qi,Jiang, Yujie,Tong, Xinyi,Pei, Jianjun,Xiao, Wei,Wang, Zhenzhong,Zhao, Linguo

, (2020)

With the aim of finding an extracellular biocatalyst that can efficiently remove the C-7 xylose group from 10-deacetyl-7-xylosltaxol, a Dictyoglomus turgidum β-xylosidase was cloned and expressed in Escherichia coli BL21 (DE3). The molecular mass of purified Dt-Xyl3 was approximately 84 kDa. The recombinant Dt-Xyl3 was most active at pH 5.0 and 75 °C, retaining 88% activity at 65 °C for 1 h, and displaying excellent stability over pH 4.0–7.5 for 24 h. In terms of kinetic parameters, the Km and Vmax values for pNPX were 0.8316 mM and 5.0178 μmol/mL·min, respectively. Moreover, Dt-Xyl3 was activated by Mn2+ and Ba2+ and inhibited by Cu2+, Ni+ and Al3+. In particular, it displayed high tolerance to salts with 60.8% activity in 20% (w/v) NaCl. Ethanol and methanol at 5–15% showed little effect on the enzymatic activity. Dt-Xyl3 demonstrated multifunctional activities followed by pNPX, pNPAraf and pNPG and had a high selectivity for cleaving the outer xylose moieties of 10-deacetyl-7-xylosltaxol with Kcat/Km 110.87 s?1/mM, which produced 10-deacetyl-taxol to semi-synthesize paclitaxel. Under the optimized conditions (60 °C, pH 4.5, enzyme dosage of 0.5 U/mL), 1 g of 10-deacetyl-7-xylosltaxol was transformed to its corresponding aglycone 10-deacetyl-taxol within 30 min, with a molar conversion of 98%. This is the first report that Dictyoglomus turgidum can produce extracellular GH3 β-xylosidase with highly specific activity for 10-deacetyl-7-xylosltaxol biotransformation, thus leading to the application of β-xylosidase Dt-Xyl3 as a biocatalyst in biopharmaceutics.

STEREOSELECTIVE DEACYLATION OF LONG-CHAIN p-NITROPHENYL N-ACYLPHENYLALANATES BY PALMITOYL-L-HISTIDINE IN A BILAYER SYSTEM

Ueoka, Ryuichi,Matsumoto, Yoko,Ninomiya, Yashushi,Nakagawa, Yoshiharu,Inoue, Kazuhiro,Ohkubo, Katsutoshi

, p. 785 - 788 (1981)

In the stereoselective deacylation of H-n-1 -CONHCH(CH2Ph)CO2-C6H4NO2-p (n=10 and 16), the bilayer catalytic systems of palmitoyl-L-histidine and double-chain surfactants (2N2Br; m=12 and 14) offered the relatively higher enantiomer rat

pH dependence of ester hydrolysis catalyzed by imidazolethiol compounds

Schneider,Wenck

, p. 1653 - 1661 (1969)

-

A Mechanistic Study on the Non-enzymatic Hydrolysis of Kdn Glycosides

Nejatie, Ali,Colombo, Cinzia,Hakak-Zargar, Benyamin,Bennet, Andrew J.

, (2022/01/13)

Sialic acids are biologically important carbohydrates that are prevalent throughout nature. We are interested in their intrinsic reactivity in aqueous solution and how such reactivity affects the design of substrates for investigation of enzymes that process these sugars. To probe the reactivity differences between two sialic acid family members N-acetylneuraminic acid and Kdn we measured the rate constants for hydrolysis of 4-nitrophenyl 3-deoxy-d-glycero-α-d-galacto-non-2-ulosonide in aqueous solution. The kinetic data is consistent with glycosidic C?O bond cleavage occurring via four mechanistic pathways, and these are: (i) hydronium ion-catalyzed hydrolysis of the neutral sugar; (ii) hydronium ion-catalyzed hydrolysis of the glycosidic carboxylate; (iii) water-catalyzed hydrolysis of the anionic glycoside; and (iv) base-promoted reaction of the anionic glycoside. To study the effects of C-5 substitution on the Kdn glycoside we made 4-nitrophenyl 5-O-methyl-α-Kdn glycoside and determined its rate constants for hydrolysis. All hydrolytic rate constants for both Kdn glycosides were larger than those reported for the parent N-acetyl-α-neuraminide. The water-catalyzed reaction (pathway iii) exhibited a βlg value of ?1.3±0.1. We conclude that the larger rate constants associated with C5-oxygen containing sialosides results from less steric congestion at the hydrolytic transition states than for the parent C-5 acetamido glycoside.

A highly photosensitive covalent organic framework with pyrene skeleton as metal-free catalyst for arylboronic acid hydroxylation

Chen, Ying,Huo, Jianqiang,Zhang, Yubao

, (2022/03/16)

Covalent organic frameworks (COFs) have been widely utilized in metal-free photocatalytic synthesis base on their excellent properties such as super conjugation, porosity and stability. In this work, we synthesized a new COF material using 1,3,6,8-Tetrakis (p-formylphenyl)pyrene (TFPPy) and 2,2′-Dimethylbenzidine (DMBZ) as basic units through Schiff base condensation reaction. The new COF (TF-DM COF) was applied as metal-free catalyst for hydroxylation of arylboronic acids. The results indicated that the extended π conjugation of COFs enhanced the absorption of visible light, and the large porosity (BET surface area: 113.782 m2g?1) accelerated the reaction rate. Good recyclability enables it with multiple applications, which result in a great reducing of the cost. This study reports that TF-DM COF has a broad application prospect as a new generation of metal-free photocatalysts for organic conversions.

Design and Synthesis of Supramolecular Phosphatases Formed from a Bis(Zn2+-Cyclen) Complex, Barbital-Crown-K+ Conjugate and Cu2+ for the Catalytic Hydrolysis of Phosphate Monoester

Rahman, Akib Bin,Okamoto, Hirokazu,Miyazawa, Yuya,Aoki, Shin

, p. 1213 - 1223 (2021/02/01)

The development of artificial mimics of natural enzymes such as hydrolases and phosphatases is one of the great challenges in bioorganic and bioinorganic chemistry and related sciences. Supramolecular strategies are one of the useful methods to construct

Process route upstream and downstream products

Process route

p-nitrophenyl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranoside
3482-57-3,4419-94-7,7344-00-5,17400-77-0,56846-39-0,78248-67-6,80446-81-7

p-nitrophenyl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranoside

4-nitrophenyl α-maltotrioside
66451-58-9

4-nitrophenyl α-maltotrioside

4-nitrophenyl α-maltotetraoside
66068-37-9

4-nitrophenyl α-maltotetraoside

p‐nitrophenyl‐α‐D-maltopentoglycoside
66068-38-0

p‐nitrophenyl‐α‐D-maltopentoglycoside

4-nitrophenyl-α-D-glucopyranoside
3767-28-0

4-nitrophenyl-α-D-glucopyranoside

Conditions
Conditions Yield
In water; at 35 ℃; Rate constant; Product distribution; acetate buffer pH 5.5, barley alpha-amylase 1 or 2;
p-nitrophenolate
14609-74-6

p-nitrophenolate

Conditions
Conditions Yield
With triethylamine; In dimethyl sulfoxide; benzene; at 25 ℃; Equilibrium constant; ionization in solvent mixtures with different ratio;
With diethylamine; In dimethyl sulfoxide; benzene; at 25 ℃; Equilibrium constant; ionization in solvent mixtures with different ratio;
With N-butylamine; In dimethyl sulfoxide; benzene; at 25 ℃; Equilibrium constant; ionization in solvent mixtures with different ratio;
In water; at 25 ℃; Rate constant;
In methanol; Equilibrium constant; equilibrium constant for dissociation; also in ethylene glycol;
4-nitrobenzenediazonium tetrafluoroborate
456-27-9

4-nitrobenzenediazonium tetrafluoroborate

4-nitro-benzenediazohydroxide, sodium salt
32352-96-8

4-nitro-benzenediazohydroxide, sodium salt

nitrobenzene
98-95-3,26969-40-4

nitrobenzene

Conditions
Conditions Yield
In acetonitrile; Product distribution; Mechanism;
4-nitrobenzenediazonium tetrafluoroborate
456-27-9

4-nitrobenzenediazonium tetrafluoroborate

Conditions
Conditions Yield
With nitrogen; In water; at 26 ℃; Product distribution;
8.3 % Chromat.
Multi-step reaction with 2 steps
1: 70 percent / acetonitrile / 12 h / Ambient temperature
2: 11 percent / potassium phenoxide / acetonitrile / 12 h / Heating
With potassium phenolate; In acetonitrile;
Multi-step reaction with 2 steps
1: 41.4 percent / acetonitrile / 12 h / Ambient temperature
2: 3.2 percent / potassium phenoxide / acetonitrile / 4 h / Heating
With potassium phenolate; In acetonitrile;
1-O-(p-Nitrophenyl)-β-D-ribofuranoside
59495-69-1

1-O-(p-Nitrophenyl)-β-D-ribofuranoside

Conditions
Conditions Yield
With water; at 100 ℃; Rate constant; various pH;
N,N-dimethylguanidine sulfate
598-65-2,1186-46-5

N,N-dimethylguanidine sulfate

p-Nitrophenyl 3-bromo-2,2-diethoxy-propionate
87224-03-1

p-Nitrophenyl 3-bromo-2,2-diethoxy-propionate

2-Dimethylamino-5,5-diethoxy-5,6-dihydro-3H-pyrimidin-4-one
117053-43-7

2-Dimethylamino-5,5-diethoxy-5,6-dihydro-3H-pyrimidin-4-one

Conditions
Conditions Yield
With sodium; Product distribution; multistep reaction: 1.) EtOH, room t., 1 h, 2.) EtOH, reflux, 16 h; reaction with var.guanidines;
With sodium; Yield given. Multistep reaction; 1.) ethanol, room t., 1 h, 2.) ethanol, reflux, 16 h;
p-nitrophenyl 2',3'-O-(o,o'-biphenylenemethylidene)ribofuranoside
116910-88-4

p-nitrophenyl 2',3'-O-(o,o'-biphenylenemethylidene)ribofuranoside

Conditions
Conditions Yield
With water; at 100 ℃; Rate constant; various pH;
p-nitrophenyl endo-2',3'-O-(1-aminocarbonyl-o,o'-biphenylenemethylidene)ribofuranoside
127086-70-8

p-nitrophenyl endo-2',3'-O-(1-aminocarbonyl-o,o'-biphenylenemethylidene)ribofuranoside

Conditions
Conditions Yield
With water; at 100 ℃; Rate constant; various pH;
p-nitrophenyl endo-2',3'-O-(1-carboxy-o,o'-biphenylenemethylidene)ribofuranoside
127179-72-0

p-nitrophenyl endo-2',3'-O-(1-carboxy-o,o'-biphenylenemethylidene)ribofuranoside

Conditions
Conditions Yield
With water; at 100 ℃; Rate constant; various pH;
p-nitrophenyl endo-2',3'-O-(1-methoxycarbonyl-o,o'-biphenylenemethylidene)ribofuranoside
127179-71-9

p-nitrophenyl endo-2',3'-O-(1-methoxycarbonyl-o,o'-biphenylenemethylidene)ribofuranoside

Conditions
Conditions Yield
With water; at 100 ℃; Rate constant; various pH;

Global suppliers and manufacturers

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  • Hangzhou Dingyan Chem Co., Ltd
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  • Chemwill Asia Co., Ltd.
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  • Hangzhou Keyingchem Co.,Ltd
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  • Career Henan Chemical Co
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