水液相下两性Lys→Mg(Ⅱ)配合物对映异构的理论研究

Theoretical Study on the Enantiomerism of Amphoteric Lys→Mg(Ⅱ)Complex in Aqueous-liquid Environment

采用基于密度泛函理论的M06-2X和MN15方法,结合处理溶剂效应的SMD模型方法,研究了水液相下两性赖氨酸二价镁配合物(Lys→Mg(Ⅱ))的对映异构.发现Lys→Mg(Ⅱ)的对映异构可通过质子转移和R基的CC键旋转过程实现.考察了3个反应通道a、b和c,它们分别是S-Lys→Mg(Ⅱ)先失去手性,然后R-基C-C键旋转,最后实现对映体异构;S-Lys→Mg(Ⅱ)先手性转变,然后R-基C-C键旋转实现对映体异构;S-Lys→Mg(Ⅱ)先从两性向中性异构,然后实现手性转变,最后通过R-基C-C键旋转实现对映体异构.计算表明,c通道最优势,隐性溶剂效应下决速步的自由能垒是204.4 k J/mol,显性溶剂效应下该能垒降到103.9-109.9 k J/mol之间.结果表明,水液相下Lys→Mg(Ⅱ)的对映异构过程很慢,赖氨酸二价镁可短期用于生命体同补赖氨酸和二价镁.

The enantiomerism of amphoteric lysine and magnesium bivalent complexes(Lys→Mg(Ⅱ))in aqueous-liquid environment was studied by using M06-2X and MN15 methods based on density functional theory and SMD model method to deal with solvent effect.It was found that the enantiomerism of Lys Mg(II)can be achieved through the process of proton transfer and the rotation of R group C-C bond.Three reaction channels a,b and c were investigated.In channel a,S-Lys→Mg(Ⅱ)loses its chirality first,then C-C bond of R group totates,and it achieves enantiomerism process finally.The reaction be achieved through the chiral flip of S-Lys→Mg(Ⅱ)and the rotation of R group C-C bond in channel b.S-Lys→Mg(Ⅱ)isomerisms from amphoteric to neutral first,then achieves chiral flip and through the rotation of R group C-C bond achieves enantiomerism reaction finally in channel c.The calculation shows that the channel c has the most advantage,its free energy barriers of step-determining is 204.4 kJ/mol under the effect of recessive solvent,the barrier could be reduced to between 103.9 and 109.9 kJ/mol under the effect of dominant solvent.The results show that the enantiomerism process of Lys→Mg(Ⅱ)is slow in aqueous-liquid environment,lysine magnesium divalent can be used to supply lysine and magnesium divalent for life simultaneously in short-term dimensions.