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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Influence of base stacking on excited-state behavior of polyadenine in water, based on time-dependent density functional calculations
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Influence of base stacking on excited-state behavior of polyadenine in water, based on time-dependent density functional calculations

机译：基于时间相关的密度泛函计算，碱基堆积对水中聚腺嘌呤激发态行为的影响

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摘要

A thorough study of the excited-state properties of the stacked dimers and trimers of 9-methyladenine in B-DNA conformation has been performed in aqueous solution by using time-dependent density functional calculations and the solvent polarizable continuum model, and results were compared with experimental results on polyadenine oligomers. The effect of base stacking on the absorption and emission spectra is fully reproduced by our calculations. Although light absorption leads to a state (S_B) delocalized over several nucleobases, excited-state geometry optimization indicates that S_B subsequently evolves into a state in which the excitation is localized on a single base. Analysis of the excited-state potential energy surfaces shows that S_B can easily decay into the lowest energy excited state, S_(CT), which is a dark excimer produced by intermonomer charge transfer between two stacked bases. The subpicosecond features of the time-resolved experiments are interpreted in terms of ultrafast decay from S_B. After localization, two easy, radiationless decay channels are indeed open for S_B: (ⅰ) ground-state recovery, according to the same mechanisms proposed for isolated adenine and/or (ⅱ) decay to S_(CT). Our calculations suggest that the slowest part of the excited-state dynamics detected experimentally involves the Scr state.
机译：通过使用时间依赖性密度泛函计算和溶剂可极化连续体模型，在水溶液中对9-甲基腺嘌呤在B-DNA构象中堆叠的二聚体和三聚体的激发态性质进行了深入研究，并将结果与聚腺嘌呤低聚物的实验结果。我们的计算完全再现了碱基堆积对吸收光谱和发射光谱的影响。尽管光吸收导致状态（S_B）在多个核碱基上离域，但激发态几何优化表明S_B随后演变为激发位于一个碱基上的状态。对激发态势能面的分析表明，S_B容易衰减为最低能量激发态S_（CT），这是由两个堆叠碱基之间的单体间电荷转移产生的暗准分子。时间分辨实验的亚皮秒级特征是根据S_B的超快衰减来解释的。定位后，确实为S_B打开了两个简单的无辐射衰减通道：（ⅰ）基态恢复，这是根据提出的用于隔离腺嘌呤和/或（ⅱ）衰减至S_（CT）的相同机制提出的。我们的计算表明，实验检测到的激发态动力学的最慢部分涉及Scr状态。

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