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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Radicals Produced by γ-Irradiation of Hyperquenched Glassy Water Containing 2'-Deoxyguanosine-5'-monophosphate
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Radicals Produced by γ-Irradiation of Hyperquenched Glassy Water Containing 2'-Deoxyguanosine-5'-monophosphate

机译：γ辐照含2'-脱氧鸟苷5'-单磷酸酯的超淬灭玻璃水产生的自由基

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摘要

Hyperquenched glassy water (HGW) has been suggested as the best model for liquid water, to be used in low-temperature studies of indirect radiation effects on dissolved biomolecules (Bednarek et al. J. Am. Chem. Soc. 1996, 118, 9387). In the present work, these effects are examined by X-band electron spin resonance spectroscopy (ESR) in y-irradiated HGW matrix containing 2'-deoxyguanosine-5'-monophosphate. Analysis of the complex ESR spectra indicates that, in addition to OH' and HO_2~. radicals generated by water radiolysis, three species are trapped at 77 K: (i) G(C8)H~. radical, the H-adduct to the double bond at C8; (ii) G~(-.) radical anion, the product of electron scavenging by the aromatic ring of the base; and (iii) dR(-H)~. radicals formed by H abstraction from the sugar moiety, predominantly at the C'5 position. We discuss the yields of the radicals, their thermal stability and transformations, as well as the effect of photobleaching. This study confirms our earlier suggestion that in HGW the H atom addition/abstraction products are created at 77 K in competition with HCV radicals, in a concerted process following ionization of water molecule at L-type defect sites of the H-bonded matrix. The lack of OH~. reactivity toward the solute suggests that the H-bonded structure in HGW is much more effective in recombining OH~. radicals than that of aqueous glasses obtained from highly concentrated electrolyte solutions. Furthermore, complementary experiments for the neat matrix have provided evidence that HO_2~. radicals are not the product of H atom reaction with molecular oxygen, possibly generated by ultrasounds used in the process of sample preparation.
机译：已建议将超淬灭玻璃水（HGW）作为液态水的最佳模型，用于低温研究对溶解的生物分子的间接辐射效应（Bednarek等人，J.Am.Chem.Soc.1996，118，9387 ）。在本工作中，通过X波段电子自旋共振光谱（ESR）在含有2'-脱氧鸟苷-5'-单磷酸盐的y辐射HGW基质中检查了这些影响。对复杂ESR光谱的分析表明，除了OH'和HO_2〜。由水辐射分解产生的自由基，在77 K下被捕获了三种：（i）G（C8）H〜。自由基，C8处双键的H加合物; （ii）G〜（-。）自由基阴离子，被碱的芳香环清除电子的产物; （iii）dR（-H）〜。 H主要从C'5位置从糖部分中抽取H形成的自由基。我们讨论了自由基的产率，其热稳定性和相变以及光漂白的影响。这项研究证实了我们较早的建议，即在HGW中，在H键合基质的L型缺陷位点将水分子电离后，与HCV自由基竞争地在77 K处产生H原子添加/吸收产物。缺少OH〜。对溶质的反应性表明，HGW中的H键结构在重组OH〜方面更为有效。自由基要比从高浓度电解质溶液中获得的水性玻璃更容易。此外，纯净基质的补充实验提供了HO_2〜的证据。自由基不是H原子与分子氧反应的产物，可能是由样品制备过程中使用的超声波产生的。

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