- An Acyl Transfer Reaction Catalyzed by an Epimerase MarH
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MarH, a small protein (129 amino acids) belonging to the cupin superfamily, was previously characterized as an epimerase involved in the (2S,3S)-β-methyltryptophan formation in the maremycin biosynthesis. Here, MarH was discovered to act as an acyltransferase that can catalyze the 3-O-acylation of chloramphenicol. Furthermore, MarH can catalyze N-acylation of deacylated chloramphenicol analogue thereby activating them for 3-O-acylation. By systematic site-directed mutagenesis, H64 was revealed as a potential catalytic base that deprotonates the acyl acceptor substrate. Nucleophilic attack at the carbonyl carbon of the acyl donor then gives the acylation product.
- Han, Mo,Yin, Haixing,Zou, Yi,Brock, Nelson L.,Huang, Tingting,Deng, Zixin,Chu, Yiwen,Lin, Shuangjun
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- Fabrication of resin supported Au-Pd bimetallic nanoparticle composite to efficiently remove chloramphenicol from water
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The evolution of antibiotic resistance and the potential impact on human health of chloramphenicol (CAP) have made it an environmental pollutant requiring urgent action. In this study, Au-Pd bimetallic nanoparticles (BNPs) were first synthesized and then successfully loaded on Amberlite 717 to form an Amberlite 717 supported Au-Pd BNP catalytic system (717@Au-Pd) with the mass fraction of Au-Pd at about 4.5%. The as-synthesized catalytic system was used to degrade CAP in water under a H2 atmosphere at room temperature. When 0.5 g of 717@Au-Pd was added into the CAP solution (50 mg L-1, 50 mL, pH 7), about 60% of CAP was absorbed on the 717@Au-Pd in the first 10 h and then all of CAP can be completely removed in the following 3 h under a H2 atmosphere. The degradation process of the reaction can be fitted with a first-order kinetics equation with the kinetics constant of 4.3 h-1 ± 0.009. The degradation products and mechanism were studied using LC/MSD Trap-XCT. The results showed that CAP was removed by the 717@Au-Pd via cleaving the carbon-halogen bond of CAP while keeping the nitro-group unaffected and this made the degradation products less environmentally toxic. The recycled experiments showed that the removal rate of CAP can still be maintained at 99% even after 5 cycles. The study indicated that 717@Au-Pd is a promising catalyst for removing environmental pollutants such as CAP containing carbon-halogen bonds.
- Wang, Xu,Wang, Yun-Xia,Yuan, Baoling,Cui, Hao-Jie,Fu, Ming-Lai
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p. 18806 - 18812
(2015/04/22)
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- ANTIMICROBIAL AGENTS
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The present invention relates to the field of anti-infective, anti-proliferative, anti-inflammatory, and prokinetic agents. More particularly, the invention relates to substituted aromatic compounds useful as therapeutic agents.
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Page/Page column 75-76
(2012/10/07)
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- Correlation between antigen-combining-site structures and functions within a panel of catalytic antibodies generated against a single transition state analog
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The diversity of the immune response, which can provide a panel of catalytic antibodies with varying degrees of catalytic activity and substrate specificity by immunization with a single hapten, raises the question concerning the extent to which a rationa
- Fujii, Ikuo,Tanaka, Fujie,Miyashita, Hideaki,Tanimura, Ryuji,Kinoshita, Keiko
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p. 6199 - 6209
(2007/10/02)
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- Reversed-phase liquid chromatographic separation of enantiomeric and diastereomeric bases related to chloramphenicol and thiamphenicol.
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The important antimicrobial agents chloramphenicol and thiamphenicol are N-acylated amines whose chemical structures include two chiral centers. Each drug is the single enantiomer of R,R configuration. The N-deacylated bases of the drugs are important intermediates in their synthesis and optical resolution. In this report, reversed-phase HPLC methods are described for the separation of enantiomeric and diastereomeric bases of the two drugs and of two closely related bases used in some syntheses of the drugs. The stereoisomeric bases were derivatized with a homochiral isothiocyanate and the resulting diastereomeric thioureas were separated on C18 columns with methanol:water mixtures as mobile phases and detection at 254 nm. The four stereoisomeric bases of chloramphenicol and those of its unnitrated analogue were thus separable after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate. This reagent also allowed the separation of the D-threo isomer of the p-mercaptomethyl analogue of thiamphenicol base from its stereoisomers. The stereoisomers of thiamphenicol base were similarly separated with (R)-alpha-methylbenzyl isothiocyanate as the derivatizing agent. The diastereomers of chloramphenicol base and of thiamphenicol base were chromatographically separable after derivatization with the nonchiral reagent benzyl isothiocyanate. The procedures developed may be useful in the determination of the stereoisomeric composition of the drugs in research and in quality control, and may be applicable to other similar agents whose chemistry and pharmacology are receiving considerable attention.
- Gal,Meyer-Lehnert
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p. 1062 - 1065
(2007/10/02)
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