Mechanism on Damage of the Purine Base in a Nucleic Acid Using the Electrogenerated Active Oxygen

体内产生活性氧，再加上突变物质产生的活性自由基。从这一角度来看，人们对活性氧的突变特性非常感兴趣。在这项工作中，我从鸟苷衍生物与产生的超氧阴离子自由基相互作用的角度研究了核酸中嘌呤碱基的损伤机理。在鸟苷存在下，氧在DMF中的可逆循环伏安曲线是不可逆的。这不是由超氧阴离子自由基介导的单电子转移，而是EC机制。反应产物经光谱、电化学和层析鉴定为鸟嘌呤及其类似物在嘌呤碱基上被破坏。从鸟苷到电生超氧阴离子自由基的质子转移导致氢过氧自由基。鸟嘌呤的生成是由氢过氧自由基歧化反应产生的过氧化氢引起的。鸟苷似乎与过氧化氢自由基反应，在嘌呤碱基上产生损坏的产物。分子轨道计算部分支持这些结论。研究发现，核酸中嘌呤碱基损伤的关键反应是从鸟苷到超氧阴离子自由基的质子转移。

Active oxygens are generated in a body, coupled with derivation of the activated free radical from mutation substances. From the point of view considerable interest is devoted to mutation character of the active oxygens. In this work, I have investigated the mechanism on damage of the purine base in a nucleic acid in terms of interaction of the guanosine derivative with electrogenerated superoxide anion radical.A reversible cyclic voltammogram of oxygen in DMF came out to be irreversible in the presence of guanosine. This arises from not a one-electron transfer mediated by superoxide anion radical but the EC mechanism. The reaction products are identified as guanine and its analog damaged in the purine base by the spectroelectrochemical and chromatographic measurements. A proton transfer from guanosine to electrogenerated superoxide anion radical leads to hydroperoxy radical. Generation of guanine is caused by hydrogen peroxide derived from the disproportionation reaction of hydroperoxy radical. It seems that guanosine reacts with hydroperoxy radical, yielding the product damaged in the purine base. Molecular orbital calculations partially support these conclusions. It has been found that the key reaction for the damage of the purine base in a nucleic acid is the proton transfer from guanosine to superoxide anion radical.