水液相下Phe分子与Na+配合物对映异构的DFT研究

该文采用DFT(密度泛函理论)的M06-2X、MN15方法和处理溶剂效应的SMD模型方法，研究了在水液相下苯丙氨酸与钠离子配合物(Phe·Na⁺)的对映异构.研究结果发现：手性Phe·Na⁺的对映异构可在质子只以氧为桥、以氧和氮联合为桥和只以氮为桥迁移的3个通道上实现.反应势能面计算结果表明：质子只以氮为桥迁移的反应通道最优势，其余2个反应通道处于劣势.在隐性水溶剂效应下优、劣通道的速度决定步骤的自由能垒分别为228.0和255.8 kJ·mol^-1,在显性水溶剂效应下优、劣通道的速度决定步骤的自由能垒分别降至111.7～122.0 kJ·mol^-1和142.2～145.8 kJ·mol^-1.研究结果表明：在水液相下手性Phe·Na⁺的消旋速度极慢，苯丙氨酸钠短期用于生命体同补苯丙氨酸和钠元素比较安全.

The Density Functional Theory Study on Enantiomeric Isomerization of Phenylalanine with Na+ Complex in Aqueous Liquid Phase

The enantiomeric isomerization of phenylalanine with sodium complex(Phe·Na⁺)in aqueous liquid is studied by using M06-2X and MN15 methods of DFT(density functional theory)and SMD model method dealing with solvent effect.It is found that the enantiomeric isomerization of chiral Phe·Na⁺ can be realized in three channels where protons use only oxygen as bridge, oxygen and nitrogen as bridge and nitrogen only as bridge.The calculation of reaction potential energy surface shows that the reaction channel of proton transfer only with nitrogen as bridge is the most dominant, and the other two reaction channels are at a disadvantage.The free energy barriers for determining the speed step of the superior and inferior channels under the recessive water solvent effect are 228.0 and 255.8 kJ·mol^-1,respectively,and under the dominant water solvent effect the two barriers are reduced to between 111.7—122.0 kJ·mol^-1 and 142.2—145.8 kJ·mol^-1,respectively.The results show that the racemization rate of chiral Phe·Na⁺ in aqueous liquid phase is very slow,and sodium phenylalanine is safe to be used as supplement of phenylalanine and sodium in short term.