2’-脱氧腺苷-5’-磷酸与羟基自由基反应所形成的自由基

运用可靠的B3LYP/DZP++方法研究了2'-脱氧腺苷-5'-单磷酸(dAMP)与羟基自由基(HO·)的反应中所产生的20余种自由基. 结果表明, 反应的初始产物包括HO·加成到dAMP碱基C8、C4位上所形成的羟基加合物自由基, 以及dAMP碱基环上氨基的脱氢自由基. 而且,反应最初形成的C4位羟基加合物自由基具有脱水产生dAMP碱基环上氨基脱氢自由基的热力学趋势, 脱水形成的两种氨基脱氢自由基都是强氧化剂.尽管HO·加成到dAMP碱基C2位上所形成的加成产物比C4位的加成产物更稳定, 但dAMP与HO·的氧原子间较强的静电排斥作用却使得HO·难以靠近C2原子, 导致C2位的羟基加成产物难以形成. 上述结论不但与有关实验结果一致, 而且还对一些实验现象作出了合理的解释.

Radicals Created fromthe Reactions of 2’-Deoxyadenosine-5’-monophosphate with Hydroxyl Radical

The radicals generated fromreactions of 2'-deoxyadenosine-5'-monophosphate (dAMP) with an HO· radical were studied by the reliable B3LYP/DZP++ method. The results show that the initial primary products are the radicals of HO· addition at the C8 and C4 sites of dAMP and those of dehydrogenation from the NH₂ moiety of dAMP. Moreover, the initial radicals of the C4 site adducts of HO· tend thermodynamically to take place dehydration reactions that yields strong oxidizing, H-abstraction radicals fromthe NH₂ group of dAMP. The electrostatic repeller interaction between the dAMP molecule and HO· results in HO· addition radicals of the C2 atomof dAMP to be a by-product, even if they are relative stable species. These theoretical results agree well with available experimental observations and give proper explanations for some experimental results.