两种最稳定构型色氨酸分子手性转变的反应机理及水溶剂化效应

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,研究两种最稳定构型色氨酸分子手性转变的反应机理及水溶剂化效应.结果表明:两种构型的色氨酸分子均有3条手性转变通道a,b,c;构型1的主反应通道为通道a,决速步骤自由能垒为256.7kJ/mol,构型2的主反应通道为通道a和c,决速步骤自由能垒分别为258.8,256.7kJ/mol,决速步骤能垒均来自于质子从手性C向氨基N迁移的过渡态;水溶剂效应使构型1的主反应通道决速步骤能垒降至113.4kJ/mol;单体色氨酸分子具有稳定性,水溶剂环境下色氨酸分子的手性转变可以缓慢进行.

Reaction Mechanism and Water Solvation Effect of Chiral Transitionof Tryptophan Molecules of Two Most Stable Configurations

We studied reaction mechanism and water solvation effect of chiral transition of tryptophan molecules of two most stable configurations 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 there are three chiral transition channels a,b and c of tryptophan molecules of two configurations. The dominant reaction channel of configuration one is channel a, and the step determining free energy barrier is 2567 kJ/mol. The dominant reaction channels of configuration two are channel band c, and the step determining free energy barriers are 258.8, 256.7 kJ/mol, respectively. The step determining free energy barriers come from the transition state of proton transfer from the chiral C to the amino N. The water solvation effect reduces the step determining energy barrier to 113.4 kJ/mol for the dominant reaction channel of the configuration one. Monomer tryptophan molecule is stable. The chiral transition of tryptophan can molecules can proceed slowly in water solvent environment.