Free radicals from polycrystalline pyrimidines and purines upon heavy ion bombardment at low temperatures: an electron spin resonance study.
Free radicals from polycrystalline pyrimidines and purines upon heavy ion bombardment at low temperatures: an electron spin resonance study.
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低温重离子轰击下多晶嘧啶和嘌呤产生的自由基：电子自旋共振研究。
DOI：
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发表时间：
1993
影响因子：
2.6
通讯作者：
G. Kraft
中科院分区：
文献类型：
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作者：
A. Schaefer;J. Hüttermann;G. Kraft
通过电子自旋共振 (ESR) 光谱研究了在约 100 K 的重离子轰击后 DNA 成分胸腺嘧啶、胞嘧啶和腺苷的多晶样品中自由基的形成。在 100 K 照射后、退火至 300 K 后以及在 300 K 下储存后，在 77 K 下观察光谱。通过计算机操作从光谱中分离出单个自由基图案，并根据文献数据通过粉末模拟将其分配给结构。胸腺嘧啶的光谱包含烯丙基自由基、5-胸腺嘧啶自由基的八位组模式以及由碳C5处的净氢增益形成的6-基自由基的贡献。后一种物质也存在于胞嘧啶中，胞嘧啶还显示出由于羧基氧 C2 处的 H 加成而产生的模式。腺苷具有两个 H-加成基团，一个位于 C2，另一个位于 C8。此外，所研究的所有 DNA 亚基的光谱均包含线宽约为 0.9 mT 的高斯单线态作为自由基成分。在低温下获得的光谱已经包含二次自由基，但表现出较大的线宽。这一特征归因于由邻近的自由基引起的偶极耦合。
The formation of free radicals in polycrystalline samples of the DNA constituents thymine, cytosine, and adenosine after bombardment with heavy ions at about 100 K was investigated by electron spin resonance (ESR) spectroscopy. Spectra were observed at 77 K after irradiation at 100 K, upon annealing to 300 K and after storage at 300 K. Individual radical patterns were isolated from the spectra by computer manipulation and assigned to structures by powder-simulations based on literature data. The spectra of thymine contain an allyl radical, the octet pattern of the 5-thymyl radical and contributions of the 6-yl radical formed by net hydrogen gain at carbon C5. The latter species is also present in cytosine which in addition displays the pattern due to H-addition at the carboxyl oxygen C2. Adenosine exhibits two H-addition radicals, one at C2, the other at C8. Additionally, the spectra of all DNA subunits studied contain as a radical component a Gaussian singlet of about 0.9 mT line width. The spectra obtained at low temperature already contain the secondary radicals but exhibit a large linewidth. This feature is attributed to dipolar coupling caused by radicals in close proximity.