Near 0 eV electrons attach to nucleotides
Near 0 eV electrons attach to nucleotides
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DOI：
10.1021/ja055615g
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发表时间：
2006-02-01
影响因子：
15
通讯作者：
Schaefer, HF
中科院分区：
文献类型：
--
作者：
Gu, JD;Xie, YM;Schaefer, HF
为了阐明由低能电子引起的DNA链断裂的新生阶段的机制，已经通过可靠校准的B3 LYP/DZP++方法（Chem.Rev.2002，102，231）进行了电子附着到核苷酸的理论研究。本文选择2 '-脱氧胞苷-3'-单磷酸（3 '-dCMPH）及其磷酸去质子化阴离子（3'-dCMP（-））作为模型。该研究表明，3 '-dCMPH能够捕获接近0 eV的电子以形成自由基阴离子，该自由基阴离子在气相和水溶液中具有比相应的中性物质更低的能量。过量电子密度主要位于核苷酸自由基阴离子的碱基上。这种嘧啶基自由基阴离子的电子脱离能足够高，使得随后的磷酸-糖C-O σ键断裂或糖苷键断裂是可行的。尽管3 '-dCMPH的以磷酸根为中心的自由基阴离子在气相中不稳定，但它在水溶液中可能是稳定的。然而，具有小于4 eV的动能的入射电子可能无法有效地在溶液或气相中产生以磷酸根为中心的自由基阴离子。本研究还表明，在水溶液中，核苷酸的电子亲合势不受反离子的影响。
To elucidate the mechanism of the nascent stage of DNA strand breakage by low-energy electrons, theoretical investigations of electron attachment to nucleotides have been performed by the reliably calibrated B3LYP/DZP++ approach (Chem. Rev. 2002, 102, 231). The 2'-deoxycytidine-3'monophosphate (3'-dCMPH) and its phosphate-deprotonated anion (3'-dCMP(-)) have been selected herein as models. This investigation reveals that 3'-dCMPH is able to capture near 0 eV electrons to form a radical anion which has a lower energy than the corresponding neutral species in both the gas phase and aqueous solution. The excess electron density is primarily located on the base of the nucleotide radical anion. The electron detachment energy of this pyrimidine-based radical anion is high enough that subsequent phosphate-sugar C-O sigma bond breaking or glycosidic bond cleavage is feasible. Although the phosphate-centered radical anion of 3'-dCMPH is not stable in the gas phase, it may be stable in aqueous solution. However, an incident electron with kinetic energy less than 4 eV might not be able to effectively produce the phosphate-centered radical anion either in solution or in the gas phase. This research also suggests that the electron affinity of the nucleotides is independent of the counterion in aqueous solution.