液相下的8-羟基鸟嘌呤的氢转移反应

HYDROGEN TRANSFER REACTION OF THE ADDUCT OF HYDROXYL RADICAL AND GUANINE(8-OHGRAD) IN SOLUTION

本文利用MPWB1K/aug-cc-pVDZ方法研究了水分子辅助的8-羟基鸟嘌呤在水溶液中的氢转移反应.通过优化该反应的反应物、过渡态和产物结构,计算最小能量路径,分析了反应过程中各个部分的电荷分布情况和水溶剂对该反应过程的贡献.计算发现,8-羟基鸟嘌呤在水溶液中的氢转移反应势垒是15.84 kcal/mol,比气相下的同一反应势垒低很多.通过对反应过程的溶剂化效应和极化效应的分析发现,水的极化效应使反应势垒增加了12.85 kcal/mol,而水的溶剂化效应使反应势垒降低了24.7 kcal/mol.因此,在水溶剂的影响下,8-羟基鸟嘌呤的氢转移反应比气相下的反应势垒降低了11.91 kcal/mol.这说明,水溶剂的存在加速了反应的进行.

In this work, we investigated the water assisted hydrogen transfer reaction of the adduct of hydroxyl radical and guanine-8-OHGrad in solution under MPWB1K/aug-cc-pVDZ level. We optimized the reactant, tran- sition state and product geometries; calculated the minimum energy pathways; analyzed the charge distribution a- long the reaction revolution and calculated the water contribution to the reaction. The calculation results showed that the reaction energy barrier of the water-assisted hydrogen transfer of 8-OHGrad radical was 15.8 kcal,/mol, which was much lower than the gas phase value. The water polarization effect on solute increased the barrier height by 12.85 kcal/mol and the solvation energy lowed the barrier height by 24.7 kcal/mol. Combining the two effects, the water contribution lowed the reaction barrier height by 11.91 kcal/mol, so we can say that the water solvent accel- erated the reaction rate.