FREE-RADICALS FROM IRRADIATED LYOPHILIZED DNA - INFLUENCE OF WATER OF HYDRATION
FREE-RADICALS FROM IRRADIATED LYOPHILIZED DNA - INFLUENCE OF WATER OF HYDRATION
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DOI：
10.1080/09553009214550981
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发表时间：
1992-03-01
影响因子：
2.6
通讯作者：
KOHNLEIN, W
中科院分区：
文献类型：
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作者：
HUTTERMANN, J;ROHRIG, M;KOHNLEIN, W
在不同相对湿度（0-95% H2O或D2O）下与水蒸气平衡的冻干DNA在77 K下进行x射线照射，并在77-280 K温度范围内用电子顺磁共振（EPR）光谱分析自由基。根据湿度、微波功率和温度的变化对光谱进行分析，通常在77 K时得到双重态和三重态光谱。该双联体部分转化为5-百里基（TH.）。含有氘化胸腺嘧啶（dTDNA）的DNA表明，“正常”DNA的双链应该由两个相似的双链组成，其中一个应该分配给胸腺嘧啶阴离子，另一个可能分配给胞嘧啶阴离子。三联体信号更加稳定，可能与鸟嘌呤阳离子或其去质子化后继物有关。在高度水化的DNA（95%湿度）中检测到其他几种模式，其中一个是烯丙基自由基。其他特征主要或只发生在相对湿度高于66%的DNA平衡中，并归因于二级结构的影响。其中一些成分可能表明H-或d -加入到胞嘧啶碱基中，这一反应也可用于dTDNA。总自由基产率和相对TH的定量分析。浓度揭示了后者优势的一个原因是其相对于其他物种的热稳定性。总自由基浓度随着目标尺寸的增加而增加，达到76%的相对湿度，水合水形成DNA的一个组成部分。在95%的相对湿度下。除了DNA自由基外，还形成了自由基，这表明冰和水合DNA已经分离成离散的目标。
Lyophilized DNA equilibrated with water vapour at various relative humidities (0-95% H2O or D2O) was X-irradiated at 77 K and analysed for free radicals by electron paramagnetic resonance (EPR) spectroscopy in the temperature range 77-280 K. Analysis of spectra according to variation in humidity, microwave power and temperature generally yielded a doublet and a triplet spectrum at 77 K. The doublet partially converted into the 5-thymyl radical (TH.). DNA containing deuterated thymine (dTDNA) revealed that the doublet of 'normal' DNA should be composed of two similar doublets, one of which should be assigned to the thymine anion, the other possibly the cytosine anion. The triplet signal was more stable and could be related to the guanine cation or its deprotonated successor. Several other patterns were detected, among them an allyl radical in highly aquated DNA (95% humidity). Other features occurred either predominantly or exclusively in DNA equilibrated above 66% relative humidity and were ascribed to an influence of the secondary structure. Among them were components possibly indicating H- or D-addition to the cytosine base, a reaction also derivable for dTDNA. Quantitative analysis of the total radical yield and the relative TH. concentration revealed that one cause of the dominance of the latter is its thermal stability vs. other species. The total radical concentration increases with target size up to 76% relative humidity, the hydration water forming an integral part of the DNA. At 95% relative humidity OH. radicals are formed in addition to DNA radicals, showing that ice and hydrated DNA have separated into discrete targets.