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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Bound anionic states of adenine
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Bound anionic states of adenine

机译：腺嘌呤的束缚阴离子态

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摘要

Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the newfound anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The new valence states observed here, unlike the dipole-bound state, could exist in condensed phases and might be relevant to radiobiological damage. The discovery of these valence anionic states of adenine was facilitated by the development of (ⅰ) an experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ⅱ) a combinatorial/quantum chemical approach for identification of the most stable tautomers of organic molecules.
机译：核酸碱基的阴离子状态与低能电子对DNA的破坏以及通过DNA的电荷转移有关。以前对游离的，未溶剂化的核酸碱基母体阴离子进行的气相研究仅探测偶极结合态，该态在浓缩相环境中不存在，但未观察到价态阴离子态，而对于嘌呤碱基而言，这些价态被认为是绝热未结合的。与此预期相反，我们证明了迄今为止被忽略的一些腺嘌呤互变异构体，它是由烯胺-亚胺转化产生的，具有电子垂直分离能高达2.2 eV的价态阴离子态，并且这些阴离子互变异构体中至少有一个是绝热的界。此外，我们预测，新的阴离子互变异构体也应在溶液中占主导地位，并且应具有比标准价阴离子更大的电子垂直脱离能值。所有这些新发现的阴离子互变异构体都可能在电子离解，然后氢原子与碳原子结合的过程中形成，它们可能会影响暴露于低能电子的DNA和RNA的结构和性质。与偶极子束缚态不同，此处观察到的新价态可能以凝聚相形式存在，可能与放射生物学损伤有关。 （ⅰ）开发用于光电子实验的核酸碱基亲本阴离子的实验方法，以及（ⅱ）组合/量子化学方法用于鉴定最稳定的互变异构体，促进了腺嘌呤这些价态阴离子状态的发现。有机分子。

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