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首页> 外文期刊>The Journal of Chemical Physics >Fourier transform infrared spectroscopic and theoretical study of water interactions with glycine and its N-methylated derivatives
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Fourier transform infrared spectroscopic and theoretical study of water interactions with glycine and its N-methylated derivatives

机译：傅里叶变换红外光谱和水与甘氨酸及其N-甲基化衍生物相互作用的理论研究

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摘要

In this study we attempt to explain the molecular aspects of amino acids hydration. Glycine and its N-methylated derivatives: N-methylglycine, N,N-dimethylglycine, and N,N,N-trimethylglycine were used as model solutes in aqueous solution, applying FT-IR spectroscopy as the experimental method. The quantitative version of the difference spectra method enabled us to obtain the solute-affected HDO spectra as probes of influenced water. The spectral results were confronted with density functional theory calculated structures of small hydration complexes of the solutes using the polarizable continuum model. It appears that the hydration of amino acids in the zwitterionic form can be understood allowing a synchronized fluctuation of hydrogen bonding between the solute and the water molecules. This effect is caused by a noncooperative interaction of water molecules with electrophilic groups of amino acid and by intramolecular hydrogen bond, allowing proton transfer from the carboxylic to the amine group, accomplishing by the chain of two to four water molecules. As a result, an instantaneous water-induced asymmetry of the carboxylate and the amino group of amino acid molecule is observed and recorded as HDO band splitting. Water molecules interacting with the carboxylate group give component bands at 2543 11 and 2467 15 cm-1, whereas water molecules interacting with protons of the amine group give rise to the bands at 2611 15 and 2413 12 cm-1. These hydration effects have not been recognized before and there are reasons to expect their validity for other amino acids.
机译：在这项研究中，我们试图解释氨基酸水合的分子方面。甘氨酸及其N-甲基化衍生物：N-甲基甘氨酸，N，N-二甲基甘氨酸和N，N，N-三甲基甘氨酸用作水溶液中的模型溶质，采用FT-IR光谱作为实验方法。差异光谱法的定量版本使我们能够获得受溶质影响的HDO光谱作为受影响水的探针。光谱结果与密度泛函理论使用可极化连续谱模型计算出的溶质的小水合配合物的结构有关。看来两性离子形式氨基酸的水合可以理解为允许溶质和水分子之间的氢键同步波动。这种作用是由于水分子与氨基酸的亲电基团的非合作相互作用以及分子内的氢键所引起的，从而使质子从羧基转移到胺基，这是通过两个到四个水分子的链来完成的。结果，观察到羧酸盐和氨基酸分子的氨基的瞬时水诱导的不对称性，并记录为HDO带分裂。与羧酸盐基团相互作用的水分子在2543 11和2467 15 cm-1处给出了能带，而与胺基质子相互作用的水分子在2611 15和2413 12 cm-1处出现了能带。这些水合作用以前没有被认识到，有理由期待它们对其他氨基酸的有效性。

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