胸腺嘧啶碱基与羟基自由基反应的密度泛函理论

Density_Functional Theory on the Reactions of Thymine with Hydroxyl Radical

羟基自由基(·OH)进攻嘧啶碱基是破坏核酸造成DNA断链损伤的重要原因之一.采用密度泛函(DFT)理论中B3LYP方法在6—31G基组水平上对胸腺嘧啶(thymine,简写为"T")受羟基自由基进攻形成的各种可能产物自由基进行几何全优化.根据总能量、键长和自旋密度的计算结果,从理论上确认了C＿5位加成机制.得稳定产物自由基T5OH·,且T5OH·不易脱水与N＿3位H脱水得一个更稳定的产物自由基.该稳定自由基的形成造成DNA断链损.

It is one of important reasons for the reaction of ·OH with thymine to destroy nucleic acid and damaged DNA. Ab initio DFT/B3LYP calculations at 6-31G basis set level were carried out for the possible product radicals of attacked thymine by ·OH. According to the calculated results of total energy, atomic spin density and bond length, the stable product radical formed by ·OH addition at C_5 was theoretically certified. T5OH· was not easy to dehydrate. The formation of stable radicals leads to damage DNA.