苏氨酸分子的构象转变及水分子与羟基自由基的催化机理

摘要

采用密度泛函理论的 B3LYP 方法和微扰论的 MP2方法,研究苏氨酸分子构象转变机制以及水分子与羟基自由基对氢迁移反应的催化作用.结果表明：S-苏氨酸向R-别苏氨酸的构象转变反应有4个通道,R-别苏氨酸向R-苏氨酸与 S-苏氨酸向 S-别苏氨酸的构象转变反应各有1个通道；S-苏氨酸向R-别苏氨酸构象转变反应的最高能垒为250.2 kJ/mol；R-别苏氨酸向 R-苏氨酸构象转变反应的最高能垒为335.0 kJ/mol；S-苏氨酸向 S-别苏氨酸构象转变反应的最高能垒为359.6 kJ/mol；2个水分子构成的链及水分子/羟基自由基构成的链对质子迁移反应有较好的催化作用,使 S-苏氨酸向 R-别苏氨酸构象转变反应的高能垒分别降为128.3 kJ/mol 和108.6 kJ/mol.%Using B3LYP methods of density functional theory and the MP2 methods of perturbation theory,we studied conformational transition mechanism of threonine molecules and catalytic action of water molecules and hydroxyl radicals in the hydrogen transfer reaction.The results show that there are four channels in the conformational transition reaction of S-Thr to R-allo-Thr.There is one channel in the conformational transitions of R-allo-Thr to R-Thr and S-Thr to S-allo-Thr.The highest energy barriers for the conformational transition of S-Thr to R-allo-Thr,R-allo-Thr to R-Thr and S-Thr to S-allo-Thr are 250.2,335.0,359.6 kJ/mol.Besides,the chain composed of two water molecules and the chain composed of hydroxyl radical and water molecules have a better catalytic effect in proton migration reaction,and the high-energy barriers are reduced to 128.3,108.6 kJ/mol for the conformational transition of S-Thr to R-allo-Thr respectively.