气相赖氨酸分子手性转变机制的理论研究

Theoretical Research on Chiral Change Mechanism of Gaseous Lysine Molecules

赖氨酸的S型和R型两种手性对映体有着不同的功能特性,本文基于密度泛函理论(DFT)的B3LYP/6-311++g(d,p)水平上的计算,对气相赖氨酸分子的手性转变过程进行研究.通过寻找反应过程中过渡态和中间体等极值点的结构,绘制了赖氨酸分子手性转变路径上完整的反应势能面.结果表明:赖氨酸分子完成从S型向R型的手性转变要经过5个过渡态和4个中间体.首先是实现氢原子在羧基内的转移,能垒为148.3kJ·mol-1;而后是手性碳上的氢原子迁移至羰基氧上,能垒为318.9kJ·mol-1,是整个反应过程的最大能垒;最后羰基的氢原子转移至手性碳原子的另一侧,实现S型到R型的手性转变.

The two kinds of chiral enantiomers of lysine have different features. In this article, we do a research on the chiral shift process of gaseous lysine molecules by calculating in B3LYP/6-311 ＋ ＋g（d, p） level based on densi ty functional theory. Furthermore, the chiral transition path reaction potential energy surface of lysine molecule is drawn by looking for the extreme value point structure of the transition state and intermediate, etc. The resuhs show that： to achieve the chiral transition of lysine from S type to R-type, five transition states and four intermediates are needed. The first is to achieve the transfer of hydrogen atoms inside the carboxyl group, which needs energy barrier 148.3 kJ mol-1. Then the hydrogen atoms on the chiral carbon transfer to the carbonyl group, which needs the greatest energy barrier 318.9 kJ mol-1 in whole process. Finally, the hydrogen atoms on the carbonyl transfer to the other side of chiral carbon atom, achieving the chiral transition from S-type to R-type.