Electron attachment to Nucleotides in aqueous solution
Electron attachment to Nucleotides in aqueous solution
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DOI：
10.1002/cphc.200600294
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发表时间：
2006-09-11
期刊：
影响因子：
2.9
通讯作者：
Schaefer, Henry F., III
中科院分区：
文献类型：
--
作者：
Gu, Jiande;Xie, Yaoming;Schaefer, Henry F., III
最近的实验和理论研究表明，DNA片段上的低能电子(Lee)可以导致DNA链断裂。因此，可靠的DNA片段的电子亲和能(EA)对于理解这种生物相关的过程是非常重要的。研究了电子与核苷和核苷酸的结合，以阐明DNA中电荷诱导断链的机制。[6-12]这些研究表明，核碱基中心阴离子的形成是低能电子作用下DNA中C±Oσ键断裂或N1±糖苷键断裂的关键步骤。溶剂对电子捕获过程的影响通常用气相结构来模拟。[6，7]必须注意的是，核苷酸中的磷酸基团在生理条件下大多是去质子化的。此外，已发现核苷酸的自由基双阴离子在气相中是不稳定的。[6]对气相中这种亚稳态双阴离子的密度泛函理论研究缺乏理论严谨性。[13]因此，需要仔细研究水溶液中磷酸基团的去质子化对核苷酸的EAs的影响。在这里，我们报告了在水溶液中电子与核苷酸的结合的研究，以努力阐明上面讨论的问题。以中性形式和去质子化形式的2о-脱氧胸苷-5-о单磷酸(记为5о-dTMPH和5о-DTMP±)为模型。为了更好地描述DNA中3о-5о磷酸二酯连接的影响，用CH3基团终止了±OPO3H部分(见方案1)。这个模型提供了与DNA的重要组成部分直接相关的信息。
Recent experimental and theoretical studies have demonstrated that low-energy electron (LEE) attachment to DNA fragments may induce strand breaks in DNA.[1–5] Reliable electron affinities (EAs) for DNA fragments are thus of great importance in understanding such biologically relevant processes. Studies of electron attachment to nucleosides and nucleotides have been performed to elucidate the mechanisms of the charge-induced strand breaks in DNA.[6–12] These investigations reveal that the formation of a nucleobase-centered radical anion is the key step for either CÀO σ bond breaking or N1Àglycosidic bond rupture in DNA subjected to low-energy electrons.[6–12] These findings raise new questions as to the influences of solvent and deprotonation on the EAs of nucleotides. Solvent effects on the electron-capture process are typically modeled with gas-phase structures.[6, 7] It must be noted that the phosphate group in nucleotides is mostly deprotonated under physiological conditions. Furthermore, radical dianions of nucleotides have been found to be unstable in the gas phase.[6] DFT studies of such metastable dianions in the gas phase lack theoretical rigor.[13] Therefore, the influence on the EAs of nucleotides, due to the deprotonation of the phosphate group in aqueous solution, needs to be examined carefully. Here, we report an investigation of electron attachment to nucleotides in aqueous solution in an effort to shed light on the problems discussed above. The 2о-deoxythymidine-5оmonophosphates in its neutral and deprotonated forms (denoted as 5о-dTMPH and 5о-dTMPÀ) have been selected as models. For a better description of the influence of the 3о-5оphosphodiester linkage in DNA, the ÀOPO3H moiety was terminated with a CH3 group (see Scheme 1). This model provides information, which is directly relevant to the important building blocks of DNA.