RADIOLYTIC PATHWAYS IN GAMMA-IRRADIATED DNA - INFLUENCE OF CHEMICAL AND CONFORMATIONAL FACTORS
RADIOLYTIC PATHWAYS IN GAMMA-IRRADIATED DNA - INFLUENCE OF CHEMICAL AND CONFORMATIONAL FACTORS
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DOI：
10.2307/3575770
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发表时间：
1982-01-01
影响因子：
3.4
通讯作者：
BERTINCHAMPS, A
中科院分区：
文献类型：
--
作者：
GREGOLI, S;OLAST, M;BERTINCHAMPS, A
几种化学和构象因素干扰了伽玛辐射DNA的辐射分解途径，在大分子上产生了不同的自由基群。这些因素包括缺氧或好氧条件、相对水化程度、变性和/或降解以及碱组成。这导致了ESR谱的极端变化。然而，对这些光谱的计算机辅助分析揭示了以下共同的组成：来自胸腺嘧啶阴离子的二联体(.ovrhdot.T-)，来自鸟嘌呤阳离子的单重态(.ovrhdot.G+)，来自5-胸腺基自由基的八重态(.ovrhdot.TH)，以及来自胸腺嘧啶定位的过氧化氢自由基的不对称双联体(TO.ovrhdot.O)。这种对实验光谱的正式解释允许阐明DNA在冷冻水溶液中辐射分解的以下基本特征。中性DNA溶液在77℃冰冻。K是相分离系统。辐射对DNA的损伤不是由辐射的间接影响造成的。DNA上的初级自由基是两个符号的离子，在组成碱基上随机产生。电荷迁移通过堆积的碱基发生。胸腺嘧啶是电子长程迁移的最终归宿。鸟嘌呤是短程正向空穴迁移的最终汇。迁移现象可能部分或全部受到各种干扰因素的阻碍。随着温度的升高，离子自由基进入转化反应：.ovrhdo.G+在不与周围水分子反应的情况下衰退，而.ovrhdot.T-确实反应生成5-胸腺基自由基。在有氧存在的情况下，生成的是过氧化氢自由基，而不是5-胸腺自由基。在本研究过程中没有检测到糖定位的自由基。
Several chemical and conformational factors interfered with the radiolytic pathways in .gamma.-irradiated DNA, producing different radical populations on the macromolecule. These factors include anoxic or oxic conditions, relative hydration degree, denaturation and/or degradation and base composition. This led to extreme variations in ESR spectra. Nevertheless, computer-assisted analysis of these spectra revealed the following common composition: a doublet from thymine anions (.ovrhdot.T-), a singlet from guanine cations (.ovrhdot.G+), an octet from 5-thymyl radicals (.ovrhdot.TH), and an asymmetrical doublet from thymine-located peroxyl radicals (TO.ovrhdot.O). This formal interpretation of the experimental spectra permitted elucidation of the following basic features for DNA radiolysis in frozen aqueous solution. Neutral DNA solutions frozen at 77.degree. K are phase-separated systems. Radiation damage to DNA does not result from the indirect effects of radiation. Primary radicals on DNA are ions of both signs, randomly produced on the constituent bases. Charge migration occurs via the stacked bases. Thymine is the eventual sink of the long-range electron migration. Guanine is the eventual sink of the short-range positive hole migration. Migration phenomena may be partially or totally hindered by various interfering factors. With increase in temperature, ionic radicals enter conversion reactions: .ovrhdot.G+ decays without reacting with the surrounding water molecules, whereas .ovrhdot.T- does react to form the 5-thymyl radical. In the presence of oxygen, peroxyl radicals TO.ovrhdot.O are formed rather than 5-thymyl radicals. No sugar-located free radicals have been detected in the course of the present investigation.