揭示胞苷的激发态动力学和激发态质子转移过程的作用,Physical Chemistry Chemical Physics

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揭示胞苷的激发态动力学和激发态质子转移过程的作用
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2023-11-06 , DOI: 10.1039/d3cp03683a
Li Zhao ₁ , Xuehui Geng ₁ , Guoxia Han ₁ , Yahui Guo ₁ , Runze Liu ₂ , Junsheng Chen ₃

Affiliation

DNA和RNA的高光稳定性与其结构单元、核碱基和核苷的光化学和光物理特性密不可分，这些特性可以以无害的方式消散吸收的紫外光能量。核苷的失活机制，特别是胞苷（Cyd）的衰变途径，一直是一个激烈争论的问题。在当前的研究中，我们采用高级电子结构计算与激发态非绝热动力学模拟相结合，以提供 Cyd 在气相和水溶液中激发态失活的清晰图像。在这两种环境中，由环褶皱运动驱动的无势垒衰变路径和由CO键的伸长运动驱动的具有小能垒的弛豫通道 [双键，长度为m-破折号]

分别被指定为<200 fs和亚皮秒衰变时间分量。核糖基团的存在对 Cyd 在气相中的动态行为有微妙的影响，因为核糖到碱的氢/质子转移过程在能量上难以实现，其能量势垒约为 1.4 eV。然而，这种能量势垒在水中显着降低，特别是当存在明确的水分子时。因此，我们认为水溶液中发现的长寿命衰变通道可以归因于 Cyd-水分子间氢/质子转移过程。本研究假设了一个新的场景，以深入了解 DNA 和 RNA 的内在光稳定性，并为揭示胞苷激发态衰变机制的长期争论提供坚实的证据，特别是对于实验观察到的时间成分的分配。

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Revealing the excited-state dynamics of cytidine and the role of excited-state proton transfer process

The high photostability of DNAs and RNAs is inextricably related to the photochemical and photophysical properties of their building blocks, nucleobases and nucleosides, which can dissipate the absorbed UV light energy in a harmless manner. The deactivation mechanism of the nucleosides, especially the decay pathways of cytidine (Cyd), has been a matter of intense debate. In the current study, we employ high-level electronic structure calculations combined with excited state non-adiabatic dynamic simulations to provide a clear picture of the excited state deactivation of Cyd in both gas phase and aqueous solution. In both environments, a barrierless decay path driven by the ring-puckering motion and a relaxation channel with a small energy barrier driven by the elongation motion of C [double bond, length as m-dash]

O bond are assigned to <200 fs and sub-picosecond decay time component, respectively. The presence of ribose group has a subtle effect on the dynamic behavior of Cyd in gas phase as the ribose-to-base hydrogen/proton transfer process is energetically inaccessible with a sizable energy barrier of about 1.4 eV. However, this energy barrier is significantly reduced in water, especially when an explicit water molecule is present. Therefore, we argue that the long-lived decay channel found in aqueous solution could be assigned to the Cyd–water intermolecular hydrogen/proton transfer process. The present study postulates a novel scenario toward deep understanding the intrinsic photostability of DNAs and RNAs and provides solid evidence to disclose the long history debate of cytidine excited-state decay mechanism, especially for the assignment of experimentally observed time components.

更新日期：2023-11-06

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