- Flash vacuum pyrolysis of 2-acetyl-3-azido[1]benzothiophene
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Flash vacuum pyrolysis (FVP) of 2-acetyl-3-azido[1]benzothiophene at 300 °C provides 3-methyl [1]benzothieno[3,2-c]isoxazole (72%). At higher temperatures, the heteroindoxyl 1,2-dihydro[1]benzo-thieno[3,2-b]pyrrol-3-one was obtained in low yield (ca. 10%). The heteroindoxyl exists as a mixture of keto and enol forms in DMSO solution. Because of the easy oxidative dimerisation of these products to indigotin (and its heteroanalogues), such reactions are excellent examples of the synthetic advantages of FVP with the monomeric products conveniently generated under vacuum in a solvent-free, air-free environment.
- Gaywood, Alexander P.,McNab, Hamish,McNab, Lilian
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p. 228 - 237
(2020/09/09)
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- Elucidating Cysteine-Assisted Synthesis of Indirubin by a Flavin-Containing Monooxygenase
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Indirubin is a biologically active compound found in Danggui Longhui Wan, which is a traditional Chinese medicine for chronic myelocytic leukemia. In the biosynthesis of indirubin, the formation of indigo, which is a stereoisomer of indirubin, is a major side reaction. Recent findings have suggested that cysteine supplementation shifts product selectivity from indigo to indirubin. Here, we disclose how cysteine is involved in enhancing the product selectivity in the synthesis of indirubin using a flavin-containing monooxygenase from Methylophaga aminisulfidivorans (MaFMO). First, cysteine reacts with indoxyl to synthesize 2-cysteinylindoleninone, inhibiting the dimerization of indoxyl. Second, the reducing power of cysteine allows MaFMO to additionally hydroxylate indoxyl toward isatin, overcoming the problem in biased distribution of two different precursors. Third, cysteine activates isatin to react with 2-cysteinylindoleninone to form indirubin. Based on this revealed mechanism, indirubin derivatives with different indole ring components were synthesized.
- Kim, Joonwon,Lee, Jeongchan,Lee, Pyung-Gang,Kim, Eun-Jung,Kroutil, Wolfgang,Kim, Byung-Gee
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p. 9539 - 9544
(2019/10/14)
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- Comprehensive kinetic and substrate specificity analysis of an arylsulfatase from Helix pomatia using mass spectrometry
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Sulfatases hydrolyze sulfated metabolites to their corresponding alcohols and are present in all domains of life. These enzymes have found major application in metabolic investigation of drugs, doping control analysis and recently in metabolomics. Interest in sulfatases has increased due to a link between metabolic processes involving sulfated metabolites and pathophysiological conditions in humans. Herein, we present the first comprehensive substrate specificity and kinetic analysis of the most commonly used arylsulfatase extracted from the snail Helix pomatia. In the past, this enzyme has been used in the form of a crude mixture of enzymes, however, recently we have purified this sulfatase for a new application in metabolomics-driven discovery of sulfated metabolites. To evaluate the substrate specificity of this promiscuous sulfatase, we have synthesized a series of new sulfated metabolites of diverse structure and employed a mass spectrometric assay for kinetic substrate hydrolysis evaluation. Our analysis of the purified enzyme revealed that the sulfatase has a strong preference for metabolites with a bi- or tricyclic aromatic scaffold and to a lesser extent for monocyclic aromatic phenols. This metabolite library and mass spectrometric method can be applied for the characterization of other sulfatases from humans and gut microbiota to investigate their involvement in disease development.
- Correia, Mário S.P.,Ballet, Caroline,Meistermann, Hannes,Conway, Louis P.,Globisch, Daniel
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p. 955 - 962
(2019/02/09)
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- New enzymatic and mass spectrometric methodology for the selective investigation of gut microbiota-derived metabolites
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Gut microbiota significantly impact human physiology through metabolic interaction. Selective investigation of the co-metabolism of bacteria and their human host is a challenging task and methods for their analysis are limited. One class of metabolites associated with this co-metabolism are O-sulfated compounds. Herein, we describe the development of a new enzymatic assay for the selective mass spectrometric investigation of this phase II modification class. Analysis of human urine and fecal samples resulted in the detection of 206 sulfated metabolites, which is three times more than reported in the Human Metabolome Database. We confirmed the chemical structure of 36 sulfated metabolites including unknown and commonly reported microbiota-derived sulfated metabolites using synthesized internal standards and mass spectrometric fragmentation experiments. Our findings demonstrate that enzymatic sample pre-treatment combined with state-of-the-art metabolomics analysis represents a new and efficient strategy for the discovery of unknown microbiota-derived metabolites in human samples. Our described approach can be adapted for the targeted investigation of other metabolite classes as well as the discovery of biomarkers for diseases affected by microbiota.
- Ballet, Caroline,Correia, Mário S. P.,Conway, Louis P.,Locher, Theresa L.,Lehmann, Laura C.,Garg, Neeraj,Vujasinovic, Miroslav,Deindl, Sebastian,L?hr, J.-Matthias,Globisch, Daniel
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p. 6233 - 6239
(2018/08/07)
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- Hemiindigo: Highly Bistable Photoswitching at the Biooptical Window
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Hemiindigo is a long known chromophore that absorbs in the blue part of the spectrum but has almost completely been ignored as potential photoswitch. Herein we show how the absorption of hemiindigo is shifted to the red part of the visible spectrum and how nearly perfect photoswitching can be achieved using blue or green and red light. Five derivatives were investigated giving very high isomeric yields in both switching directions, i.e. >90% E isomer after irradiation with 470 to 530 nm light and 99% Z isomer with 590 up to 680 nm light. At the same time the thermal bistability is extraordinarily high leading to half-lives of the pure isomeric states of up to 83 years at 25 °C. The herein developed photoswitches show photochromism in the visible enabling the two isomeric states to be distinguished by the naked eye. Substituted hemiindigos therefore constitute extremely promising new photoswitches with excellent properties for applications in biology, chemistry, or material sciences.
- Petermayer, Christian,Thumser, Stefan,Kink, Florian,Mayer, Peter,Dube, Henry
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supporting information
p. 15060 - 15067
(2017/11/03)
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- Determination of acetylcholinesterase and butyrylcholinesterase activity without dilution of biological samples
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Two cholinesterases: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), are known. The enzymes are important in the body and alteration of their activity has significant use in the diagnosis of poisoning, liver function, etc. Currently available methods for the determination of cholinesterases have some major drawbacks including various interferences and the inability to be used for decreasing the enzyme activity in the presence of reversible inhibitors due to sample dilution; hence, a method for dilution free assay of cholinesterases is desired. Here, microplates were modified with indoxylacetate (100 μL of 10 mmol L-1 solution) and used for cholinesterases assay after drying at 37 °C. The fact that indoxylacetate remains stable in dry state and serves simultaneously as a chromogen and substrate provide good prerequisites for the method. The limit of detection for BChE was 0.71 U while that for AChE was 2.8 U per a 100 μL sample (solution of enzyme or plasma sample). The limit of detection is low enough to allow standard examination of cholinesterasemia. The two cholinesterases can be distinguished from each other using selective inhibitors such as donepezil and iso-OMPA. The new method was also successfully validated for the standard Ellman's assay using plasma samples with BChE activity adjusted by carbofuran. The new method based on indoxylacetate seems promising for routine tests.
- Pohanka, Miroslav
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p. 1044 - 1049
(2015/06/08)
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- Pullulan encapsulation of labile biomolecules to give stable bioassay tablets
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A simple and inexpensive method is reported for the long-term stabilization of enzymes and other unstable reagents in premeasured quantities in water-soluble tablets (cast, not compressed) made with pullulan, a nonionic polysaccharide that forms an oxygen impermeable solid upon drying. The pullulan tablets dissolve in aqueous solutions in seconds, thereby facilitating the easy execution of bioassays at remote sites with no need for special reagent handling and liquid pipetting. This approach is modular in nature, thus allowing the creation of individual tablets for enzymes and their substrates. Proof-of-principle demonstrations include a Taq polymerase tablet for DNA amplification through PCR and a pesticide assay kit consisting of separate tablets for acetylcholinesterase and its chromogenic substrate, indoxyl acetate, both of which are highly unstable. The encapsulated reagents remain stable at room temperature for months, thus enabling the room-temperature shipping and storage of bioassay components.
- Jahanshahi-Anbuhi, Sana,Pennings, Kevin,Leung, Vincent,Liu, Meng,Carrasquilla, Carmen,Kannan, Balamurali,Li, Yingfu,Pelton, Robert,Brennan, John D.,Filipe, Carlos D. M.
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p. 6155 - 6158
(2014/06/23)
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- Structural characterization and function determination of a nonspecific carboxylate esterase from the amidohydrolase superfamily with a promiscuous ability to hydrolyze methylphosphonate esters
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The uncharacterized protein Rsp3690 from Rhodobacter sphaeroides is a member of the amidohydrolase superfamily of enzymes. In this investigation the gene for Rsp3690 was expressed in Escherichia coli and purified to homogeneity, and the three-dimensional structure was determined to a resolution of 1.8 ? The protein folds as a distorted (β/α)8-barrel, and the subunits associate as a homotetramer. The active site is localized to the C-terminal end of the β-barrel and is highlighted by the formation of a binuclear metal center with two manganese ions that are bridged by Glu-175 and hydroxide. The remaining ligands to the metal center include His-32, His-34, His-207, His-236, and Asp-302. Rsp3690 was shown to catalyze the hydrolysis of a wide variety of carboxylate esters, in addition to organophosphate and organophosphonate esters. The best carboxylate ester substrates identified for Rsp3690 included 2-naphthyl acetate (kcat/Km = 1.0 × 105 M-1 s-1), 2-naphthyl propionate (k cat/Km = 1.5 × 105 M-1 s -1), 1-naphthyl acetate (kcat/Km = 7.5 × 103 M-1 s-1), 4-methylumbelliferyl acetate (kcat/Km = 2.7 × 103 M-1 s-1), 4-nitrophenyl acetate (kcat/Km = 2.3 × 105 M-1 s-1), and 4-nitrophenyl butyrate (kcat/Km = 8.8 × 105 M -1 s-1). The best organophosphonate ester substrates included ethyl 4-nitrophenyl methylphosphonate (kcat/Km = 3.8 × 105 M-1 s-1) and isobutyl 4-nitrophenyl methylphosphonate (kcat/Km = 1.1 × 104 M-1 s-1). The (SP)-enantiomer of isobutyl 4-nitrophenyl methylphosphonate was hydrolyzed 10 times faster than the less toxic (RP)-enantiomer. The high inherent catalytic activity of Rsp3690 for the hydrolysis of the toxic enantiomer of methylphosphonate esters make this enzyme an attractive target for directed evolution investigations.
- Xiang, Dao Feng,Kumaran, Desigan,Swaminathan, Subramanyam,Raushel, Frank M.
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p. 3476 - 3485
(2014/06/23)
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- Methylene meldrums acid derivatives of indoxyl and their cyclization reactions under flash vacuum pyrolysis conditions
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Pure indoxyl can be obtained in 75% yield by flash vacuum pyrolysis (FVP) of 2′-azidoacetophenone at 650 °C. Reaction of indoxyl with methoxymethylene Meldrums acid takes place at the 1-position, and FVP of the resulting derivative provides 1-hydroxy-9H-pyrrolo[1,2-a]indol-9-one (54%). FVP of the isomeric 2-methylene compound gives pyrano[3,2-b]indol-2(5H)-one (42%). Georg Thieme Verlag Stuttgart · New York.
- Gaywood, Alexander P.,McNab, Hamish
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experimental part
p. 1361 - 1364
(2010/07/02)
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- Trypsin substrate and diganostic device, and method of using same
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A compound of the formula (I) (I) wherein R1 is a protecting group for Nα, R2 is a protecting group for NG, and R3 is aryl, and wherein the compound of formula (I) is a trypsin substrate such that trypsin cleaves the O—C single bond, which liberates R3—OH; a diagnostic device comprising same; a method for preparing the diagnostic device; and a method of using the diagnostic device to detect levels of urinary trypsin inhibitor in a biological sample; and a diagnostic kit for detecting levels of urinary trypsin inhibitor in a biological sample.
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- Directed evolution of the fatty-acid hydroxylase P450 BM-3 into an indole-hydroxylating catalyst
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The self-sufficient cytochrome P450 BM-3 enzyme from Bacillus megaterium catalyzes subterminal hydroxylation of saturated long-chain fatty acids and structurally related compounds. Since the primary structure of P450 BM-3 is homologous to that of mammalian P450 type II, it represents an excellent model for this family of enzymes. During studies on the directed evolution of P450 BM-3 into a medium-chain fatty-acid hydroxylase, several mutants, in particular the triple mutant Phe87Val, Leu 188Gln, Ala74Gly, were observed to hydroxylate indole, producing indigo and indiruhin at a catalytic efficiency of 1365M-1s-1 (kcat=2.73 s-1 and Km,=2.0mM). Both products were unequivocally characterized by NMR and MS analysis. Wild-type P450 BM-3 is incapable to hydroxylate indole. These results demonstrate that an enzyme can be engineered to catalyze the transformation of substrates with structures widely divergent from those of its native substrate.
- Li, Qing-Shan,Schwaneberg, Ulrich,Fischer, Peter,Schmid, Rolf D.
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p. 1531 - 1536
(2007/10/03)
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- Tautomerism of the Monohydroxy Derivatives of Five-Membered O, N, and S Heterocycles
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The O-deuterated enolic tautomers 3-deuteroxybenzofuran, 3-deuteroxybenzothiophene, 3-deuteroxyindole, 3-deuteroxy-1-methylindole, 3-deuteroxyfuran, 3-deuteroxythiophene, 2-deuteroxybenzothiophene, and 2-deuteroxythiophene have been generated in solution in mixtures of CD3COCD3, CD3CN, or CD3SOCD3 with D2O by hydrolysis of their trimethylsilyl derivatives in the presence of DCl (1E-3 - 1E-4 M) and characterized by 1H NMR spectroscopy.Solutions of 3-hydroxypyrrole and of 3-hydroxy-1-methylpyrrole were obtained by methanolysis of their trimethylsilyl derivatives,evaporation of the methanol, and immediate dissolution in DMSO-d6.The carbocyclic analogues of the bicyclic heterocyclic enols 3-deuteroxyindene and 2-deuteroxyindene were also generated in solution.Attempts to prepare solutions of 2-deuteroxyfuran, 2-deuteroxypyrrole, and 2-deuteroxy-1-methylpyrrole were unsuccessful.The kinetics of ketonization of the OH forms of these enols have been investigated in water or aqueous acetonitrile solution.The equilibrium constants for the keto-enol tautomerism were also determined either by direct measurement when sufficient enol was present at equilibrium or as the ratio of the rate constant for enolization of the keto form to that for ketonization of the enol form, the former being determined by the iodine-trapping technique.The effect of solvent on the equilibrium constants was also studied.Sufficient data were available for the equilibrium between 3-hydroxyindole and 3-ketoindole for them to be analyzed by the four-parameter equation of Mills and Beak to yield an a value of 2.4 and a b value of -3.0.The pKas of the bicyclic enols were measured. 3-Hydroxybenzofuran and3-hydroxybenzothiophene are stronger acids than 3-hydroxyindole and 3-hydroxy-1-methylindole.The ketonization reactions are general acid and general base catalyzed and their mechanisms are discussed.
- Capon, Brian,Kwok, Fu-Chiu
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p. 5346 - 5356
(2007/10/02)
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- 2,2-Disubstituted-1,2-dihydro-3H-indol-3-ones by Base- and Thermal-induced Cyclisations of o-Azidophenyl s-Alkyl Ketones and o-Azidobenzoyl Esters
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o-Azidophenyl s-alkyl ketones in ethanolic potassium hydroxide at room temperature undergo loss of nitrogen and cyclisation to 2,2-dialkyl-1,2-dihydro-3H-indol-3-ones in high yield.Kinetic data (E(act.) 62.4 and 71.6 kJ mol-1, respectively) obtained for the o-azidophenylisopropyl and o-azidophenylcyclohexyl ketones support an assisted nitrogen loss from the azide via the enolate ion, rather than a nitrene reaction. 1,2-Dihydro-3H-indol-3-ones, along with in some cases 2,1-benzisoxazoles, have been obtained by the thermolysis and spray vacuum pyrolysis of other o-azidophenyl alkyl ketones, diethyl o-azidobenzoyl malonate, and ethyl o- azidobenzoyl(phenyl)acetate.
- Azadi-Ardakani, Manouchehr,Alkhader, Mohamed A.,Lippiatt, John H.,Patel, Dalpat I.,Smalley, Robert K.,Higson, Susan
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p. 1107 - 1112
(2007/10/02)
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