水液相环境下赖氨酸旋光异构及羟自由基致其损伤的机理

在MP2/6-311++G(2-df,pd-)//B3LYP/6-31+G(d,p)双理论下, 采用自洽反应场(SCRF)理论的SMD模型方法, 研究水液相环境下, 两种稳定构象赖氨酸分子基于氨基氮为氢迁移桥梁的旋光异构过程及羟自由基致其损伤的机理. 势能面计算结果表明： 在水液相环境下, 当2个和3个水分子簇作为氢迁移媒介时, 构象1旋光异构的决速步骤Gibbs自由能垒分别为116.02,112.71 kJ/mol, 构象2旋光异构的决速步骤Gibbs自由能垒分别为110.27,114.29 kJ/mol； 当羟自由基与水分子链作为氢迁移媒介时, 羟自由基抽氢致赖氨酸分子构象1和构象2损伤的Gibbs自由能垒分别为-53.06,-56.05 kJ/mol, 均为无势垒反应. 即在水液相环境下, 赖氨酸分子可缓慢地旋光异构, 羟自由基可迅速致赖氨酸损伤.

Mechanism of Lysine Optical Isomerism and Lysine Damage Inducedby Hydroxyl Radicals in Water Liquid Phase Environment#br#

Using MP2/6-311++G(2-df,pd-)//B3LYP/6-31+G(d,p)double theory and SMD model method for self consistent reaction field (SCRF) theory, we studied the optical isomerism process of two stable conformation lysine molecules based on amino nitrogen as hydrogen transport bridge inwater liquid phase environment. The calculation of potential energy surface shows when the two and three water clusters areused as hydrogen transport medium, the rate determining step Gibbs free energybarriers of conformation 1 optical isomer are 11602,11271 kJ/mol, respectively. The rate determining step Gibbs free energy barriers of conformation 2 optical isomer are 11027,11429 kJ/mol, respectively. When hydroxyl radical and water molecule chain are used as hydrogen transport medium, the Gibbs free energy barriers of conformation 1 and 2 damage induced by hydroxyl radical pumping hydrogen are -5306,-5605 kJ/mol, indicating no barrier reaction. The results show that under the water liquid phase environment, lysinemolecules can be slowly optical isomers, and hydroxyl radicals can quicklycause lysine damage.