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首页> 外文期刊>New Journal of Chemistry >The regulatory roles of metal ions (M~(+/2+) = Li~+,Na~+,K~+,Be~(2+),Mg~(2+),and Ca~(2+)) and water molecules in stabilizing the zwitterionic form of glycine derivatives
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The regulatory roles of metal ions (M~(+/2+) = Li~+,Na~+,K~+,Be~(2+),Mg~(2+),and Ca~(2+)) and water molecules in stabilizing the zwitterionic form of glycine derivatives

机译：金属离子的调节作用（M〜（+ / 2+）= Li〜+，Na〜+，K〜+，Be〜（2 +），Mg〜（2+）和Ca〜（2+））和水分子稳定甘氨酸衍生物的两性离子形式

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The regulatory roles of metal ions (M~(+/2+) = Li~+,Na~+,K~+,Be~(2+),Mg~(2+),and Ca~(2+)) and water molecules in stabilizing the zwitterionic form of glycine derivatives are discussed in the present paper.The involved glycine conformers are (1) the glycine zwitterion (OO),which can bind an ion to form the salt-bridge-form derivative,and (2) two neutral forms (NO and OH),which can bind the ion with both the carboxyl oxygen and the amino nitrogen (NO),or both the carboxyl oxygen and the hydroxyl oxygen (OH) to form charge-solvated structures.Results show that four water molecules can make the OO-mode glycine-Li~+/Na~+/K~+ derivatives more stable than each of the corresponding NO-mode counterparts.Similarly,two water molecules can make the OO-mode glycine-Be~(2+) more stable than its corresponding NO-mode counterpart,while the OO-mode glycine-Mg~(2+)/Ca~(2+) are always more stable than their corresponding NO counterparts whether there is a water molecule(s) attached or not.No OH-mode glycine-Be~(2+)/Mg~(2+)/Ca~(2+) hydrates are observed because the large electrostatic effect of these divalent metal ions makes the OH-mode hydrates degenerate into the OO-mode ones.For the non-hydrated or monohydrated glycine-Li~+/Na~+ isomers,the global minimum derives from the NO-mode structure.Their (di-tetra)hydrates,however,prefer the OH-mode to the other two.For all these different glycine-K~+ hydrates,each OH-mode structure is always the global minimum among the corresponding isomers,as for the non-hydrated reactant (glycine-K~+).These predictions are consistent with other theoretical and experimental results.Most of the relative binding strengths,between a metal ion and its corresponding ligand,of the three modes are in good agreement with the relative stabilities,i.e.,the larger the binding energy is,the more stable the structure would be.Some exceptions to the agreement are explained.A comparison of binding strengths shows that the smaller the ion radius is,the greater its binding strength would be.For instance,Li-NO centre dot W (-50.5 kcal mol~(-1)) > Na-NO centre dot W (-36.4 kcal mol~(-1)) > K-NO centre dot W (-25.4 kcal mol~(-1)).
机译：金属离子的调节作用（M〜（+ / 2+）= Li〜+，Na〜+，K〜+，Be〜（2 +），Mg〜（2+）和Ca〜（2+））本文讨论了稳定稳定两性离子形式的甘氨酸衍生物的水分子。涉及的甘氨酸构象异构体是（1）甘氨酸两性离子（OO），它可以与离子结合形成盐桥形式的衍生物，和（ 2）两种中性形式（NO和OH），它们可以使离子与羧基氧和氨基氮（NO）或羧基氧和羟基氧（OH）结合形成电荷溶剂化的结构。结果表明四个水分子可以使OO型甘氨酸-Li〜+ / Na〜+ / K〜+衍生物比每个相应的NO模式对应物更稳定。类似地，两个水分子可以使OO型甘氨酸-Be〜+ 〜（2+）比其对应的NO模式稳定剂更稳定，而OO模式甘氨酸-Mg〜（2 +）/ Ca〜（2+）始终比其对应的NO模式稳定剂更稳定是否附着OH模式糖观察到ine-Be〜（2 +）/ Mg〜（2 +）/ Ca〜（2+）水合物，因为这些二价金属离子的巨大静电作用使OH型水合物退化为OO型水合物。对于非水合或一水合的甘氨酸-Li〜+ / Na〜+异构体，全局最小值源自NO-模式结构。但是，它们的（di-tetra）水合物优先于其他两个模式为OH-模式。这些不同的甘氨酸-K〜+水合物，对于非水合反应物（甘氨酸-K〜+），每个OH型结构始终是相应异构体中的整体最小值。这些预测与其他理论和实验结果一致。三种模式中金属离子与其相应配体之间的大多数相对结合强度与相对稳定性非常吻合，即结合能越大，结构越稳定。结合强度的比较表明，离子半径越小，其结合力越大。例如，Li-NO中心点W（-50.5 kcal mol〜（-1））> Na-NO中心点W（-36.4 kcal mol〜（-1））> K-NO中心点W （-25.4 kcal mol〜（-1））。

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