Ma Jun, Denisov Sergey A, Marignier Jean-Louis, Pernot Pascal, Adhikary Amitava, Seki Shu, Mostafavi Mehran
Department of Molecular Engineering, Graduate School of Engineering , Kyoto University , Nishikyo-ku, Kyoto 615-8510 , Japan.
Laboratoire de Chimie Physique , UMR 8000 CNRS/Université Paris-Sud , Bât. 349 , Orsay 91405 Cedex , France.
J Phys Chem Lett. 2018 Sep 6;9(17):5105-5109. doi: 10.1021/acs.jpclett.8b02170. Epub 2018 Aug 24.
The primary localization process of radiation-induced charges (holes (cation radical sites) and excess electrons) remains poorly understood, even at the level of monomeric DNA/RNA models, in particular, in an aqueous environment. We report the first spectroscopic study of charge transfer occurring in radiolysis of aqueous uridine 5'-monophosphate (UMP) solutions and its components: uridine, uracil, ribose, and phosphate. Our results show that prehydrated electrons effectively attach to the base site of UMP; the holes in UMP formed by either direct ionization or reaction of UMP with the radiation-mediated water cation radical (HO) facilely localize on the ribose site, despite the fact that a part of them were initially created on either the phosphate or uracil. The nature of phosphate-to-sugar hole transfer is characterized as a barrierless intramolecular electron transfer with a time constant of 2.5 ns, while the base-to-sugar hole transfer occurs much faster, within a 5 ps electron pulse.
辐射诱导电荷（空穴（阳离子自由基位点）和过量电子）的主要定位过程仍知之甚少，即使在单体DNA/RNA模型层面也是如此，尤其是在水性环境中。我们报告了第一项关于尿苷5'-单磷酸（UMP）水溶液及其成分（尿苷、尿嘧啶、核糖和磷酸盐）辐射分解过程中电荷转移的光谱研究。我们的结果表明，预水合电子有效地附着在UMP的碱基位点上；UMP中由直接电离或UMP与辐射介导的水阳离子自由基（HO）反应形成的空穴很容易定位在核糖位点上，尽管其中一部分最初是在磷酸盐或尿嘧啶上产生的。磷酸到糖的空穴转移的性质被表征为无势垒的分子内电子转移，时间常数为2.5纳秒，而碱基到糖的空穴转移发生得更快，在5皮秒的电子脉冲内。
