谷氨酸分子的手性转变及溶剂化效应

采用密度泛函理论的B3LYP方法,微扰理论的MP2方法及自洽反应场(SCRF)理论的SMD模型方法,研究两种稳定构型谷氨酸分子的手性转变及水溶剂化效应.结果表明:构型1的优势通道为通道a和通道b,决速步骤自由能垒分别为242.3,245.7kJ/mol;构型2的优势通道为通道a,决速步骤自由能垒为243.5kJ/mol;决速步骤能垒均由质子从手性C向氨基N迁移的过渡态产生;水溶剂化效应使构型1的优势通道决速步骤自由能垒降至101.5kJ/mol;决速步骤的反应速率常数在298.15K时为1.002×10~(-5)s~(-1),在310.00K时为3.802×10~(-5)s~(-1).可见谷氨酸分子在生命体内富水环境下可缓慢地实现旋光异构.

Chiral Transition and Solvation Effect of Glutamic Acid Molecules

We studied the chiral transition and water solvation effect of two kinds of the most stable configurations of glutamic acid molecules by using the B3LYP method of density functional theory, the MP2 method of perturbation theory, and SMD model method of self consistent reaction field (SCRF) theory. The results show that the dominant channels of the configurationone are channel a and channel b, step determining free energy barriers are 242.3, 245.7 kJ/mol, respectively. The dominant channel of the configuration two is the channel a, and step determining free energy barrier is 243.5 kJ/mol which is generated by the transition state of proton transfer from the chiral carbon to the amino N. The water solvation effect enables the step determining energy barrier is reduced to 101.5 kJ/mol for the dominant channel of the configuration one. The step determining reaction rate is 1.002×10^-5s^-1 at 298.15 K, and it is 3.802×10^-5 s^-1 at 310.00 K. So the glutamic acid molecules can slowly realize optical isomerism in the life rich water environment.