- Structure of a Clostridium botulinum C143S thiaminase I/thiamin complex reveals active site architecture
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Thiaminases are responsible for the degradation of thiamin and its metabolites. Two classes of thiaminases have been identified based on their three-dimensional structures and their requirements for a nucleophilic second substrate. Although the reactions of several thiaminases have been characterized, the physiological role of thiamin degradation is not fully understood. We have determined the three-dimensional X-ray structure of an inactive C143S mutant of Clostridium botulinum (Cb) thiaminase I with bound thiamin at 2.2 A resolution. The C143S/thiamin complex provides atomic level details of the orientation of thiamin upon binding to Cb-thiaminase I and the identity of active site residues involved in substrate binding and catalysis. The specific roles of active site residues were probed by using site directed mutagenesis and kinetic analyses, leading to a detailed mechanism for Cb-thiaminase I. The structure of Cb-thiaminase I is also compared to the functionally similar but structurally distinct thiaminase II.
- Sikowitz, Megan D.,Shome, Brateen,Zhang, Yang,Begley, Tadhg P.,Ealick, Steven E.
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- Mechanistic studies on thiaminase I: Identification of the product of thiamin degradation in the absence of the nucleophilic cosubstrate
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Thiaminase I catalyzes the decomposition of thiamin under basic conditions in the absence of the nucleophilic cosubstrate. The product of this reaction was identified as the adduct resulting from the displacement of the thiazole moiety of thiamin by the r
- Wu, Min,Papish, Elizabeth T.,Begley, Tadhg P.
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- Oxygen Vacancy-Engineered PEGylated MoO3 ?x Nanoparticles with Superior Sulfite Oxidase Mimetic Activity for Vitamin B1 Detection
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Sulfite oxidase (SuOx) is a molybdenum-dependent enzyme that catalyzes the oxidation of sulfite to sulfate to maintain the intracellular levels of sulfite at an appropriate low level. The deficiency of SuOx would cause severe neurological damage and infant diseases, which makes SuOx of tremendous biomedical importance. Herein, a SuOx mimic nanozyme of PEGylated (polyethylene glycol)-MoO3 ?x nanoparticles (P-MoO3 ?x NPs) with abundant oxygen vacancies created by vacancy-engineering is reported. Their level of SuOx-like activity is 12 times higher than that of bulk-MoO3. It is also established that the superior increased enzyme mimetic activity is due to the introduction of the oxygen vacancies acting as catalytic hotspots, which allows better sulfite capture ability. It is found that vitamin B1 (VB1) inhibits the SuOx mimic activity of P-MoO3 ?x NPs through the irreversible cleavage by sulfite and the electrostatic interaction with P-MoO3 ?x NPs. A colorimetric platform is developed for the detection of VB1 with high sensitivity (the low detection limit is 0.46 μg mL?1) and good selectivity. These findings pave the way for further investigating the nanozyme which possess intrinsic SuOx mimicing activity and is thus a promising candidate for biomedical detection.
- Chen, Yuan,Chen, Tongming,Wu, Xiaoju,Yang, Guowei
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- Characterization of 2-methyl-4-amino-5-(2-methyl-3-furylthiomethyl)pyrimidine from thermal degradation of thiamin
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Thiamin hydrochloride was thermally degraded in phosphate buffer (pH 6.5) at 110 °C for 2 h. A major decomposition product was isolated by column chromatography and structurally identified by spectrometric techniques (1H NMR, 13C NMR
- Jhoo, Jin-Woo,Lin, Ming-Chi,Sang, Shengmin,Cheng, Xiaofang,Zhu, Nanqun,Stark, Ruth E.,Ho, Chi-Tang
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- Kinetics and mechanistic study of manganese(II)-catalyzed cerium(IV) oxidation of thiamine hydrochloride in aqueous perchloric acid medium by stopped flow technique
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The kinetics of the manganese(II)-catalyzed oxidation of thiamine hydrochloride by cerium(IV) in aqueous perchloric acid medium at a constant ionic strength of 1.10 mol dm-3 was studied spectrophotometrically at 15, 25, 35, and 45 C by the stopped flow technique. The reaction between thiamine hydrochloride and cerium(IV) in the acid medium exhibits 1:3 stoichiometry. The main products were identified by spot test, IR, 1H NMR, and GC-MS studies. The reaction is first order in cerium(IV) and manganese(II) and has less than unit order in thiamine hydrochloride. As the acid concentration increases the rate of reaction decreases. The added product cerium(III) retards the rate of reaction. The active catalyst and oxidant species were identified as [Mn(H2O)4]2+ and [Ce(OH)]3+, respectively. A probable mechanism involving free radicals and the formation of a complex between substrate and catalyst is proposed. The reaction constants, activation parameters, and thermodynamic quantities are calculated and discussed.
- Naik,Byadagi,Nandibewoor,Chimatadar
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- Assessing and utilizing esterase specificity in antimicrobial prodrug development
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As a class of enzymes, esterases have been investigated for decades and have found use in industrial processes, synthetic organic chemistry, and elsewhere. Esters are functional groups composed of an alcohol moiety and a carboxylic acid moiety. Although much work has explored the influence of the carboxyl moiety of an ester on its susceptibility to esterases, little work has explored the influence of the alcohol moiety. Here, we describe an in vitro methodology to explore the influence of changing the alcohol moiety of an ester on its enzymatic hydrolysis, including strategies for analyzing such data. We then describe leveraging data from these assays to develop targeted antimicrobial prodrugs that activate in certain species due to the discriminatory activity of species-specific esterases. We envisage the potential of genomics and machine learning to further these efforts. Finally, we anticipate the potential future uses of these ideas, including developing targeted anti-cancer compounds.
- Hetrick, Kenton J.,Raines, Ronald T.
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- Synthetic method of thiazoles (by machine translation)
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4 - Acetoxy 3 - acetyl -3 - chloropropyl acetate is hydrolyzed under acidic conditions to prepare 4 -mercapto -2 - methyl -2 - (β - acetoxyethyl)-thiazole; the step of preparing -2 - methyl -2 - (β - acetoxyethyl)-thiazole with 3 - methyl -3 - (β - acetoxyethyl)-thiazole under acidic condition is carried out under an acidic condition by adding an oxidizing agent under an acidic condition in 3 -chloro -3 -methyl 2 - (β - acetoxyethyl)-thiazole in an acidic condition under an acidic condition by adding 4 - an oxidizing agent under an acidic condition; and a -5 - method -5 - for synthesizing thiazoles -4 - and -5 -mercapto 2 -methyl-ethyl)-thiazole in an acidic condition by adding an -5 - oxidizing agent under an -5 - 4 - acidic condition; and the method comprises the following steps: preparing -4 -4 - ethyl acetoxyethyl)-thiazole. The synthesis method is mild in overall reaction condition, simple in post-treatment and suitable for pilot scale test and industrial production. (by machine translation)
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Paragraph 0016; 0020-0021; 0025-0026; 0030
(2020/09/16)
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- KHF2: A mild and selective desilylating agent for phenol tert-butyldimethylsilyl (TBDMS) ethers
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TBDMS (t-BuMe2Si, tert-butyldimethylsilyl) ethers of a variety of phenols have been deprotected with KHF2 in MeOH, at room temperature. Carboxylic ester and labile phenolic acetate were unaffected under these conditions. In competition reactions between TBDMS ethers of a phenol and two primary benzylic alcohols, the phenolic ether underwent cleavage whereas the alcohol ethers remained intact. From a substrate containing both a phenolic hydroxyl group and a secondary, doubly benzylic hydroxyl group protected as TBDMS ethers, the phenol was rapidly and selectively released. Cleavage of TBDMS, TBDPS, and TIPS ethers of a phenol was also compared. TBDMS and TBDPS ethers underwent cleavage at room temperature within 30 minutes, whereas removal of the TIPS ether required 2.5 hours. Ease of cleavage appears to be TBDMS ≈ TBDPS > TIPS. At 60°C, TBDMS ethers of primary benzylic, allylic, and unactivated alcohols can be efficiently desilylated over a prolonged period (13-17 h). Thus, KHF2 proves to be a mild and effective reagent for the selective desilylation of phenol TBDMS ethers at room temperature.
- Lakshman, Mahesh K.,Tine, Fatou A.,Khandaker, Tashrique A.,Basava, Vikram,Agyemang, Nana B.,Benavidez, Michael S.A.,Ga?i, Marikone,Guerrera, Lisa,Zajc, Barbara
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supporting information
p. 381 - 385
(2017/02/10)
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- Biosynthesis of a thiamin antivitamin in clostridium botulinum
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Bacimethrin-derived 2′-methoxythiamin pyrophosphate inhibits microbial growth by disrupting metabolic pathways dependent on thiamin-utilizing enzymes. This study describes the discovery of the bacimethrin biosynthetic gene cluster of Clostridium botulinum A ATCC 19397 and in vitro reconstitution of bacimethrin biosynthesis from cytidine 5′-monophosphate.
- Cooper, Lisa E.,O'Leary, Seán E.,Begley, Tadhg P.
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p. 2215 - 2217
(2014/05/06)
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- Synthesis of [thiazolium-2,2′-14C2]-SAR97276A from [14C]-thiourea
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[thiazolium-2,2′-14C2]-SAR97276A, a bis(thiazolium) antimalarial development candidate, was synthesized from [ 14C]-thiourea with an overall radiochemical yield of 15%. The synthetic route involves a modified procedure for the synthesis of [ 14C]-sulfurol, also a key intermediate in thiamine synthesis, which was developed due to unlabelled chemistry proving irreproducible with the radiolabelled substrate. Copyright
- Herbert, John M.,Le Strat, Franck,Oumeddour, Delphine G.,Passey, Stephen C.,Taylor, Keith,Whitehead, David M.
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experimental part
p. 89 - 92
(2011/10/02)
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- Mechanistic investigation of the oxidation of vitamin B1 with sodium N-chlorobenzenesulfonamide in presence of ruthenium(III) catalyst in hydrochloric acid medium: A kinetic approach
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The oxidative cleavage of vitamin B1 (thiamine hydrochloride, THM) with sodium N-chlorobenzenesulfonamide (chloramine-B, CAB) has been kinetically investigated in HCl medium in presence of ruthenium(III) catalyst at 308 K. The oxidation reaction follows the rate law, -d[CAB]/dt = k [CAB] [Ru(III)] [H+] [THM]a [Cl-]b, where a and b are less than unity. Variation of ionic strength of the medium and addition of the reaction product, benzenesulfonamide (BSA) had no significant effect on the reaction rate. The change in relative permittivity of the medium affected by changing the solvent composition with acetonitrile has been studied. The stoichiometry of the reaction was found to be 1:1, and N-[(4-amino-2- methylpyrimidine-5-yl)methyl]benzensulfonamide and 2-(4-methylthiazol-5-yl) ethanol were identified as the oxidation products of vitamin B1. The reaction constants involved in the mechanism were computed. The reaction was studied at different temperatures and the overall activation parameters have been evaluated. C6H5SO2NHCl has been postulated as the reactive oxidizing species. The observed results have been explained by plausible mechanisms and the relative rate laws have been deduced.
- Mohana, Kikkeri N.,Prasad, Ningegowda,Rai, Kuriya M. L.
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experimental part
p. 1203 - 1210
(2009/12/04)
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- Effect of pH on the maillard reaction of [C]xylose, cystein, and thiamin
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The influence of different pH values, ranging from 4.0 to 7.0, on the formation of sulfur volatiles in the Maillard reaction was studied using a model system with [13C5]xylose, cysteine, and thiamin. The use of 13C-labeled xylose allowed, by analysis of the mass spectra, volatiles that incorporated xylose carbons in the molecule from other carbon sources to be discerned. For 2-furaldehyde and 2-furfurylthiol, which were favored at low pH, the labeling experiments clearly indicated that xylose was the exclusive carbon source. On the other hand, xylose was virtually not involved in the formation of 3-mercapto-2-butanone, 4,5-dihydro-2-methyl-3- furanthiol, and 5-(2-hydroxyethyl)-4-methylthiazole, which apparently stemmed from thiamin degradation. Both xylose and thiamin seemed to significantly contribute to the formation of 2-methyl-3-furanthiol, 3-mercapto-2-pentanone, and 2-mercapto-3-pentanone, and therefore different formation pathways must exist for each of these molecules. In general, the pH determined strongly which volatiles were formed, and to what extent. However, the relative contribution of xylose to the C-skeleton of a particular compound changed only slightly within the investigated pH range, when both xylose and thiamin were involved in the formation.
- Cerny, Christoph,Briffod, Matthieu
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scheme or table
p. 1552 - 1556
(2009/10/01)
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- Thiazole, imidazole and oxazole compounds and treatments of disorders associated with protein aging
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Provided are, among other things, compounds of formula I or IA, . Also provided are methods of treatment with such compounds.
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- Method for treating glaucoma IIB
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Provided is a method of decreasing intraocular pressure or improving ocular accommodation in an animal, including a human, comprising administering an intraocular pressure decreasing amount or ocular accommodation improving amount of a compound of the formula I or IA, wherein J is oxygen, sulfur, or N—Rd.
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- Novel compounds and their use
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A compound of the general formula (I): wherein R1, R2, X, Y and Z are as described in the specification.
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- Preparation and Reactivity of Model Compounds Related to Oligomers from Thiamin. A Mechanism for Oligomerization
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Compounds were synthesized having a pyrimidilmethyl groups as found in oligomers formed from thiamin.These compounds contain two such groups and a thiazole, phenylthio, or sulfonato substituent at terminal methylene position and undergo nucleophilic substitution with aqueous sulfite ion.Comparison of the rate constants for reaction with sulfite ion involving a bis(pyrimidine) and 1'-methylthiaminium ion, both having the same thiasole leaving group, reveals that an N-pyrimidinylmethyl substituent increases reactivity over that by an N-methyl griup by factor of 19.Other comparisons show that a thiazole is replaced about 1.9 times faster than a pyrimidine ring by the action of sulfite ion.Addoitives can increase or decrease by induction period for the oligomerization of thiamin chloride in methanol.A mechanism similar to that for sulfite ion substitution is suggested for oligomerization; a key feature is the conversion of thiamin to a more reactive oligomer by quaternization with introduces a pyrimidinmethyl unit.
- Zoltewicz, John A.,Uray, Georg,Kauffmann, Glenn M.
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p. 4900 - 4904
(2007/10/02)
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