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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical study of the reduction mechanism of sulfoxides by thiols
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Theoretical study of the reduction mechanism of sulfoxides by thiols

机译：硫醇还原亚砜机理的理论研究

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摘要

Theoretical computations have been carried out to investigate the reaction mechanism of the sulfoxide reduction by thiols in solution. This reaction is a suitable model for enzymatic processes involving methionine sulfoxide reductases (Msrs). Recent investigations on the Msr mechanism have clearly shown that a sulfenic acid intermediate is formed on the catalytic cysteine of the active site concomitantly to the methionine product. In contrast, experimental studies for the reaction of a number of thiols and sulfoxides in solution did not observe sulfenic acid formation. Only, a disulfide was identified as the final product of the process. The present study has been carried out at the MP2/6-311+G(3d2f, 2df, 2p)//B3LYP/6-311G(d,p) level of theory. The solvent effect in DMSO has been incorporated using a discrete-continuum model. The calculations provide a basic mechanistic framework that allows discussion on the apparent discrepancy existing between experimental data in solution and in the enzymes. They show that, in the early steps of the process in solution, a sulfurane intermediate is formed the rate of which is limiting. Then, a proton transfer from a second thiol molecule to the sulfurane leads to the formation of either a sulfenic acid or a disulfide though the latter is much more stable than the former. If a sulfenic acid is formed in solution, it should react with a thiol molecule making its experimental detection difficult or even unfeasible.
机译：已经进行了理论计算以研究溶液中硫醇还原亚砜的反应机理。该反应是涉及蛋氨酸亚砜还原酶（Msrs）的酶促过程的合适模型。对Msr机理的最新研究清楚地表明，在蛋氨酸产物的同时，在活性位点的催化半胱氨酸上形成了亚硫酸中间体。相反，溶液中许多硫醇和亚砜反应的实验研究未观察到亚硫酸的形成。仅将二硫化物鉴定为该方法的最终产物。本研究是在MP2 / 6-311 + G（3d2f，2df，2p）// B3LYP / 6-311G（d，p）的理论水平上进行的。 DMSO中的溶剂效应已使用离散连续模型纳入其中。计算提供了一个基本的机制框架，该框架允许讨论溶液和酶中实验数据之间存在的明显差异。他们表明，在溶液中的方法的早期步骤中，形成硫烷中间体的速度是有限的。然后，质子从第二硫醇分子转移到硫烷导致形成亚磺酸或二硫化物，尽管后者比前者稳定得多。如果在溶液中形成亚硫酸，它应与硫醇分子反应，从而使其实验检测变得困难甚至不可行。

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