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100-02-7Relevant articles and documents
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 carbon (AC) promoted ozone oxidation, which helps developing a mechanism involving HO{radical dot} radical. For a compound which is quite easy to oxidise, like 2,4-dichlorophenol (2,4-DCP) conventional ozonation is efficient enough to remove the initial molecule. The mechanism involved mainly consists of an electrophilic attack on the aromatic ring, which is activated by the donor effect of the -OH group, then followed by a 1,3 dipolar cycloaddition (Criegee mechanism) that leads to aliphatic species, mainly carboxylic acids. Yet, the addition of AC, through the presence of HO{radical dot} radical, enhances the removal of these species which are more refractory. For a refractory compound like nitrobenzene (NB), with a de-activated aromatic ring because of the attractive effect of -NO2, conventional ozonation is inefficient. On the contrary, this molecule can be quite easily removed with AC promoted oxidation and it is found that the mechanism (electrophilic attack followed by a 1,3 dipolar cycloaddition) is quite similar to the one corresponding to conventional ozonation, but with less selectivity. For both molecules, a mass balance has established that the by-products accounting for more than 75% of the remaining COD can be quantified. A significant part is composed of carboxylic acids (acetic, oxalic, etc.), which could afterwards be easily removed in an industrial wastewater treatment process followed by a final biological treatment step.
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 methyl aryl phosphate diesters (6) was studied at sspH 9.8 in methanol at 25.0 ± 0.1°C. Plots of kobs vs [3:Zn(II)2: -OCH3]free for all members of 6 show saturation behavior from which KM and kcatmax were determined. The second order rate constants for the catalyzed reactions (k catmax/KM) for each substrate are larger than the corresponding methoxide catalyzed reaction (k2-OMe) by 1.4 × 108 to 3 × 109-fold. The values of kcatmax for all members of 6 are between 4 × 10 11 and 3 × 1013 times larger than the solution reaction at sspH 9.8, with the largest accelerations being given for substrates where the departing aryloxy unit contains ortho-NO 2 or C(=O)OCH3 groups. Based on the linear Bronsted plots of kcatmax vs sspK aof the phenol, βIg values of -0.57 and -0.34 are determined respectively for the catalyzed methanolysis of regular substrates that do not contain the ortho-NO2 or C(=O)OCH3 groups, and those substrates that do. The data are consistent with a two step mechanism for the catalyzed reaction with rate limiting formation of a catalyst-coordinated phosphorane intermediate, followed by fast loss of the aryloxy leaving group. A detailed energetics calculation indicates that the catalyst binds the transition state comprising [CH3O -:6]?, giving a hypothetical [3:Zn(II) 2:CH3O-:6]? complex, by -21.4 to -24.5 kcal/mol, with the strongest binding being for those substrates having the ortho-NO2 or C(=O)OCH3 groups.
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 similarities. The N-15 and the bridge O-18 isotope effects for the reaction of the pNPS anion are very similar to those of the p-nitrophenyl phosphate (pNPP) dianion. This indicates that in the transition states for both reactions the leaving group bears nearly a full negative charge resulting from a large degree of bond cleavage to the leaving group. The nonbridge O-18 isotope effects support the notion that the sulfuryl group resembles SO3 in the transition state. The reaction of the neutral pNPS species in acid solution is mechanistically similar to the reaction of the pNPP monoanion. In both cases proton transfer from a nonbridge oxygen atom to the leaving group is largely complete in the transition state. Despite their mechanistic similarities, the phosphoryl- and sulfuryl-transfer reactions differ markedly in their response to medium effects. Increasing proportions of the aprotic solvent DMSO to aqueous solutions of pNPP cause dramatic rate accelerations of up to 6 orders of magnitude, but only a 50-fold rate increase is observed for pNPS. Similarly, phosphoryl transfer from the pNPP dianion to tert-amyl alcohol is 9000-fold faster than the aqueous reaction, while the sulfuryl transfer from the pNPS anion is some 40-fold slower. The enthalpic and entropic contributions to these differing medium effects have been measured and compared.