单水协同作用下甲硫氨酸分子的手性转变机制

Chiral Transition Mechanism of Methionine Molecule under Cooperative Action of Mono-H_2O

基于密度泛函理论的B3LYP方法,在6-311+G(2df)基组水平上研究单水协同作用下的甲硫氨酸(Met)分子手性转变反应过程,寻找Met分子手性反应过程中各中间体与过渡态的极值点结构,绘制单水协同作用下完整的Met分子手性转变路径反应势能面,并分析各极值点的几何和电子结构特性.结果表明:单水协同作用下S型Met分子手性C上的H原子以羧基内10O-19O原子为桥梁,转移至手性C原子的另一侧,实现从S型到R型Met分子的手性转变;该路径有4个中间体和5个过渡态,最大反应能垒为199.275 5kJ/mol,来源于第2个过渡态TS_2-S-Met&1H_2O-2.

Using the B3LYP method of density functional theory,we investigated the chiral transition process of the methionine molecule under the cooperative action of mono-H_2O at the level of 6-311＋G（2df）.We drawed a complete chiral transition path reaction potential energy surface by finding structures of the extreme value points including the transition states and intermediates,and analyzed the geometric and electronic structure properties of extreme value points.The results show that the hydrogen atom on the chiral carbon atom of S-methionine molecule can transfer to the other side of the carbon atom via the 10O-19O atoms of carboxyl atoms as a bridge,and achieve the chiral transition of methionine molecule from S-type to R-type.On this path there are four intermediates and five transition states.The maximum reaction energy barrier is 199.275 5 kJ/mol,which comes from the second transition state TS_2-S-Met1H_2O-2.