【摘要】 基于密度泛函理论考察水环境下α-丙氨酸分子手性转变机制,通过寻找水环境下α-丙氨酸手性转变过程过渡态及中间体等极值点的结构,绘制水环境下α-丙氨酸分子手性碳上氢原子转移及形成中间体异构过程的反应势能面.结果表明:与孤立条件的手性转变过程相比,以单个和两个水分子为桥梁的氢原子从手性碳向羰基氧转移过程的能垒从325.5kJ/mol分别降为200.6,173.0kJ/mol;氢原子从羰基氧再迁移到手性碳另一侧的能垒从229.2kJ/mol分别降为105.3,73.5kJ/mol.这是由于水分子在α-丙氨酸分子对映体手性转变过程中具有催化作用,即生命体内存在微量右旋丙氨酸的机制是水参与了左旋丙氨酸手性转变过程,降低了反应能垒所致.更多还原

【Abstract】 Based on density functional theory,theα-alanine molecule chiral transition mechanism in water was investigated. Having found the structures of heterogeneous transition states and intermediates at peak energy values ofα-alanine in water,we drew up the potential energy surface of chiral hydrogen transfer isomerization processesα-alanine molecule in water.Compared with the isolated chiral transition,those with single or two water molecules as hydrogen transfer bridges made the transfer process energy barrier for H from chiral C to carbonyl O reduced from 325.5kJ/mol to200.6,173.0kJ/mol respectively,and the energy barrier for H from carbonyl O to the other side of chiral C reduced from 229.2kJ/mol to 105.3,73.5kJ/mol respectively.The results reveal water molecules catalyze the chiral enantiomer transformation process ofα-alanine,illustrating apossible source of a very small amount of D-alanine in vivo,which is due to water participiting in L-alanine chiral transition.更多还原