Ab Initio Molecular Orbital Study on Molecular and Hydration Structures of Ectoine
Ab Initio Molecular Orbital Study on Molecular and Hydration Structures of Ectoine
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四氢嘧啶分子和水合结构的从头算分子轨道研究
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
S. Nagata
中科院分区：
文献类型：
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作者：
K. Suenobu;M. Nagaoka;T. Yamabe;S. Nagata
本文首次通过从头算分子轨道（MO）方法研究了嗜盐和耐盐微生物中最重要的相容溶质之一异托碱（2-甲基-4-羧基-3,4,5,6-四氢嘧啶）的分子结构和水合结构。假设其电子结构为两性离子形式，并通过几何优化寻找其在气相中可能的稳定分子结构。在MP2/6-31G*水平下获得了两种稳定的结构，其稳定性几乎相同。一种是COO基团在轴向位置另一种是平伏位置。在MP2/6-31G*水平上，得到了COO基团位于赤道位置的两性离子外酯和中性外酯之间质子转移的过渡态（TS）。然而，质子转移的能量势垒对所使用的基组敏感，并在MP2/6-31G**//MP2/6-31G*水平上消失，表明zwitte…
The molecular and hydration structures of ectoine (2-methyl-4-carboxy-3,4,5,6-tetrahydropyrimidine), which is one of the most important compatible solutes in halophilic and halotolerant microorganisms, were investigated for the first time via ab initio molecular orbital (MO) calculations. The electronic structure of ectoine was assumed to be a zwitterionic form, and possible stable molecular structures in the gas phase were searched by geometry optimizations. Two stable structures were obtained at the MP2/6-31G* level, and their stability were almost the same. One has the geometry in which the COO group is in axial position and the other in equatorial position. The transition state (TS) of proton transfer between the zwitterionic ectoine where the COO group is in equatorial position and neutral ectoine was obtained at the MP2/6-31G* level. However, the energy barrier of the proton transfer was sensitive to the basis sets used and disappeared at the MP2/6-31G**//MP2/6-31G* level, indicating that the zwitte...