RADIATION INDUCED SULFHYDRYL AUTOXIDATION AND THE OER

本项目的主要目标是阐明硫醇对 在缺氧条件下照射后DNA中发生的自由基过程 和有毒条件。这些研究将测试三种化学品模型 氧增强效应，并将研究自由基机制， 硫醇辐射防护。这些研究将采用电子自旋共振 通过质谱、HPLC和GC-质谱进行分析，并在 强调辐射直接影响的条件。通过 冷冻的缺氧和氧化的DNA-硫醇溶液的照射和 仔细分析电子自旋共振谱， 涉及DNA阴离子、阳离子和中性转移的机制 将阐明不同电荷的硫醇的自由基位点。hplc和 将采用GC-MS鉴定样品中的DNA和巯基产物 ESR分析。产品分析将测试阐明的机制 的ESR。从这个分析中，O2在与DNA自由基反应中的作用 并与硫醇自由基将被确定。主要的DNA自由基， 最容易与硫醇反应，硫醇基的身份 将测定这些反应中产生的中间体。反应 将搜索带有DNA的亚砜基。二硫化物的作用 阴离子自由基的化学氧增强效应将得到阐明 通过对一系列二硫化物的研究单个DNA碱基离子 在核苷酸上会形成自由基， 研究，以阐明自由基转移的效率， 每一个不同的基地。在这些模型系统的后期工作中， 还将研究多核苷酸和寡核苷酸。的作用 组蛋白的自由基转移过程中的带电硫醇将是 也被调查了。多胺如精胺也可用作 竞争性结合剂。改变相对浓度 巯基/结合物种将提供进一步的洞察的重要性， 巯基结合自由基转移，并作为模型的影响， 组蛋白-DNA相互作用对自由基转移到硫醇的影响。

The primary goal of this project is to elucidate the effect of thiols on the free radical processes that occur in DNA after irradiation under anoxic and oxic conditions. These studies will test three models for the chemical oxygen enhancement effect and will investigate free radical mechanisms for thiol radioprotection. The studies will employ electron spin resonance spectroscopy and HPLC and GC-mass spectroscopy and are performed under conditions that emphasize the direct effect of radiation. Through the irradiation of frozen anoxic and oxygenated DNA-thiol solutions and the careful analysis of electron spin resonance spectra the free radical mechanisms involved in the transfer of DNA anionic, cationic and neutral radical sites to thiols of differing charge will be elucidated. HPLC and GC-MS will be employed to identify DNA and thiol products in the samples analyzed by ESR. The product analyses will test the mechanisms elucidated by ESR. From this analysis the role of O2 in reactions with DNA radicals and with thiol radicals will be determined. The primary DNA radicals which react most readily with thiols, and the identity of the thiol radical intermediates produced in these reaction will be determined. Reactions of sulfoxyl radicals with DNA will be searched for. The role of the disulfide anion radical in the chemical oxygen enhancement effect will be elucidated by an investigation of a series of disulfides. Individual DNA base ion radicals will be formed on nucleotides and their reaction with thiols investigated in order to elucidate the efficiency of radical transfer from each of the various bases. At a later stage of work on these model systems polynucleotides and oligonucleotides will also be investigated. The role of histones on the radical transfer process to charged thiols will be investigated as well. Polyamines such as spermine will also be employed as competitive binding agents. Changing the relative concentration of thiol/binding species will provide further insight into the importance of thiol binding to radical transfer and act as a model for the effect of histone-DNA interactions on radical transfer to thiols.