ESR study of DNA base cation radicals produced by attack of oxidizing radicals
ESR study of DNA base cation radicals produced by attack of oxidizing radicals
复制标题
氧化自由基攻击产生 DNA 碱基阳离子自由基的 ESR 研究
DOI：
10.1021/j150608a021
复制
发表时间：
1981
期刊：
影响因子：
--
通讯作者：
K. Morehouse
中科院分区：
文献类型：
--
作者：
M. Sevilla;D. Suryanarayana;K. Morehouse
含DNA碱和类似物的水玻璃(8M NaClO/sub4/，12M LiCl)的ESR研究表明，在77K时，玻璃中产生的氧化物种(羟基自由基和Cl/sub2//sup-/)在升温后攻击一些碱及其类似物，产生…pi…-阳离子自由基。产生..皮..的化合物..阳离子包括胸腺嘧啶、尿嘧啶、3-甲基尿嘧啶、6-甲基尿嘧啶、玫瑰花酸、异玫瑰花酸、鸟嘌呤和腺嘌呤。不能产生..皮..的化合物..阳离子有1-甲基胸腺嘧啶、胸腺嘧啶核苷和1-甲基尿嘧啶。形成..pi..的整体反应..阳离子组成如下：碱+羟基(Cl/sub2//sup-/)..->；.OH/sup-/(2Cl/sup-/)+碱阳离子。嘧啶类化合物还具有pH和取代基依赖性。在位置1的氮被质子化的PHS中，不形成..pi..-阳离子自由基。此外，当位置1上有取代基时，..pi.未发现阳离子。DNA碱基的ESR波谱分析借助于计算机模拟进行了超精细裂解的阳离子和g值。分析结果与光解产生的几种DNA碱阳离子和直接产生的DNA碱阳离子的值一致。辐射。
ESR investigations of ..gamma..-irradiated aqueous glasses (8 M NaClO/sub 4/, 12 M LiCl) containing DNA bases and analogues show that oxidizing species produced in the glasses (hydroxyl radicals and Cl/sub 2//sup -/) at 77 K attack a number of the bases and their analogues after warming to produce ..pi..-cation radicals. Compounds which produce ..pi.. cations include thymine, uracil, 3-methyluracil, 6-methyluracil, orotic acid, isoorotic acid, guanine, and adenine. Compounds which are not found to produce ..pi.. cations are 1-methylthymine, thymidine, and 1-methyluracil. The overall reaction for formation of the ..pi.. cations is as follows: base + OH.(Cl/sub 2//sup -/) ..-->.. OH/sup -/(2Cl/sup -/) + base cation. A pH and substituent dependence is also noted for the pyrimidines. At pHs where the nitrogen at position 1 is protonated, ..pi..-cation radicals are not formed. In addition, when there are substituents at position 1, ..pi.. cations are not found. Analysis of the ESR spectra of the DNA base ..pi.. cations for hyperfine splittings and g values were performed by aid of computer simulations. The analyses are in agreement with values found for several DNA base cations produced by photolysis and by direct ..gamma.. irradiation.