水环境下基于氨基作氢迁移桥梁α-丙氨酸的手性转变机制  

Chiral transition mechanism of α-lalanine molecule under the water environment based on anmino used as hydrogen transfer bridges

作　　者：王彦全[1] 王佐成[1] 闫红彦[2] 佟华[1] 

机构地区：[1]白城师范学院物理学院,吉林白城137000 [2]白城师范学院计算机科学学院,吉林白城137000

出　　处：《中山大学学报（自然科学版）》2016年第5期57-65,共9页Acta Scientiarum Naturalium Universitatis Sunyatseni

基　　金：吉林省科技发展计划资助项目(20130101131JC)

摘　　要：采用密度泛函理论的B3LYP方法、微扰理论的MP2方法和自洽反应场(SCRF)理论的smd模型方法,研究了α-丙氨酸在水环境下基于氨基作氢迁移桥梁的手性转变机理。结构分析表明:7元环过渡态a TS2·2H_2O和9元环过渡态a TS2·3H_2O的键角1C-13H-14O和18O-15H-6N,比5元环过渡态a TS2·1H_2O的键角1C-13H-14O和14O-15H-6N明显增大。反应通道研究发现:手性转变反应有两个通道,一是手性碳上的H只以氨基为桥迁移到手性碳另一侧,实现手性转变;二是手性碳的H先迁移到羰基,然后再以氨基为桥迁移到手性碳另一侧,实现手性转变。势能面计算表明:第一通道为优势反应通道,H从手性碳向氨基迁移过程是决速步骤,3个水分子作为氢迁移媒介时,决速步能垒被降到122.5 k J·mol^(-1)。研究结果表明:水分子对α-丙氨酸分子内的质子迁移反应具有较好的催化作用,水溶剂效应使非质子转移反应的能垒略有升高。Based on anmino used as hydrogen transfer bridges, chiral transition mechanism of α-alanine molecule was studied under the water environment through the B3 LYP methods of density functional theory and the MP2 methods of perturbation theory as well as the stud models of SCRF. The result of structural analysis suggested that the bond angles 1C -13H- 140 and 180 -15H-6N between transition state aTS2 · 2H2O of seven membered ring and aTS2· 3H2O of nine membered ring were significantly larger than that 1C- 13H- 140 and 140- 15H-6N of transition state aTS2 ·1H2O of five membered ring. There were two channels in the ehiral transition reaction, in which one the hydrogen of chiral carbon used the imino N as a bridge and was transferred to the other side to achieve chiral transition, the other that was firstly transferred to carbonyl and then to the other side using amino as a bridge. Calculations of potential energy surface showed that the first channel was the dominant reaction channel, where the process of the hydrogen from chiral carbon to amino was the rate determining step and the energy barrier is reduced to 122.5 kJ · mo1^-1 when using three water molecules as transfer media. The water molecules had good catalytic effect on the proton transfer in α-Ala molecule, and the solvent effect on water made the energy barrier of the non proton transfer reaction increase slightly.

关 键 词：手性转变 α-Ala 密度泛函理论 微扰理论 自洽反应场 过渡态 

分 类 号：O641.12[理学—物理化学]