甘氨酸离子态构象蜕变计算

目的：研究甘氨酸（Gly）阳离子态、阴离子态和两性离子态在气相真空、油相环己烷和水相环境中的构象蜕变行为。方法：运用CAM-B3LYP和B3LYP方法在6-311＋＋G（2d，p）基组水平上对Gly不同离子态，进行几何结构、电子结构、振动分析和热力学函数计算，并运用极化连续模型（PCM）考察溶剂效应。结果：在气相、油相和水相3种环境中得到阳离子态的构象分别有3、3、5种，阴离子态的构象有1、1、3种；3种环境中只有极性强的水相中得到1种两性离子态构象且与中性分子态能量差别不大。两种方法计算得到键角一致，前者计算得到键长稍短，后者能量稍低。结论：Gly在不同环境中构象变化行为不同，环境极性增加，有利于离子态存在。

Theoretical study on the conformation disintegration of ionic Glycine

Objective：To study the conformation disintegration of glycine in cationic, anionic, and zwit-terionic states in gas phase and solvent environments with cyclohexane and water. MethodThe geometric and electronic structures, vibrational frequencies, thermodynamic functions of ionic glycine were calculated fully at the CAM-B3LYP and B3LYP theory levels using 6-311＋＋G （2d, p） basis set. The solvent effects were dealt with the polarizable continuum model （PCM）. ResultTo the cationic state, there were 3, 3, and 5 conformers, and to the anionic state, only 1, 1, and 3 conformers existed in three environments, but there was only 1 zwitterionic conformer in the water environment and its energies were higher slightly than the most stable neutral conformer. Two methods got the similar properties values but the former optimized bonds distances were shorter slightly and the latter obtained energy values were a little lower. Conclusion：The conformation disintegration of ionic gly-cine in different environments is different. The polarity of solvent increases, then more polar conformers may be presented.