DNA damage induced via dissociative attachment by low-energy electrons (0 to 20 eV) is well studied in both gas and condensed phases. However, the reactivity of ultrashort-lived prehydrated electrons ([Formula: see text]) with DNA components in a biologically relevant environment has not been fully explored to date. The electron transfer processes of [Formula: see text] to the DNA nucleobases G, A, C, and T and to nucleosides/nucleotides were investigated by using 7-ps electron pulse radiolysis coupled with pump-probe transient absorption spectroscopy in aqueous solutions. In contrast to previous results, obtained by using femtosecond laser pump-probe spectroscopy, we show that G and A cannot scavenge [Formula: see text] at concentrations of ≤50 mM. Observation of a substantial decrease of the initial yield of hydrated electrons ([Formula: see text]) and formation of nucleobase/nucleotide anion radicals at increasing nucleobase/nucleotide concentrations present direct evidence for the earliest step in reductive DNA damage by ionizing radiation. Our results show that [Formula: see text] is more reactive with pyrimidine than purine nucleobases/nucleotides with a reactivity order of T > C > A > G. In addition, analyses of transient signals show that the signal due to formation of the resulting anion radical directly correlates with the loss of the initial [Formula: see text] signal. Therefore, our results do not agree with the previously proposed dissociation of transient negative ions in nucleobase/nucleotide solutions within the timescale of these experiments. Moreover, in a molecularly crowded medium (for example, in the presence of 6 M phosphate), the scavenging efficiency of [Formula: see text] by G is significantly enhanced. This finding implies that reductive DNA damage by ionizing radiation depends on the microenvironment around [Formula: see text].

中文翻译：

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预水合电子对水溶液中核碱基和核苷酸的反应性。

低能电子（0至20 eV）通过离解性附着诱导的DNA损伤在气相和冷凝相中都得到了很好的研究。然而，迄今为止，尚未充分探索超短命的预水合电子（在化学上相关的环境中）与DNA组分的反应性。通过使用7 ps电子脉冲辐射解离结合泵浦探针瞬态吸收光谱法研究水溶液中[分子式]的电子转移过程，从而将其转移至DNA核碱基G，A，C和T以及向核苷/核苷酸的转移。与以前使用飞秒激光泵浦光谱法获得的结果相反，我们表明G和A在浓度≤50 mM时不能清除[分子式：见正文]。观察到水合电子的初始产率大幅降低（[公式：见文字]）和在增加的核碱基/核苷酸浓度下形成核碱基/核苷酸阴离子基团，为最早通过电离辐射减少DNA损伤的步骤提供了直接证据。我们的结果表明，[式：见正文]与嘧啶的反应性比嘌呤核苷/核苷酸的反应性高，依次为T> C> A>G。此外，对瞬态信号的分析表明，该信号是由于生成的阴离子自由基与初始[公式：参见文本]信号的损失直接相关。因此，我们的结果与先前提出的在这些实验的时间范围内在核碱基/核苷酸溶液中瞬态负离子的解离不一致。此外，在分子拥挤的介质中（例如，在6 M磷酸盐存在下），G的[公式：参见文字]的清除效率显着提高。这一发现表明，电离辐射对DNA的还原性损害取决于[公式：参见文本]周围的微环境。