嘧啶碱基衍生物激发态动力学理论与实验研究

项目名称： 嘧啶碱基衍生物激发态动力学理论与实验研究

项目编号： No.21303198

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 数理科学和化学

项目作者： 羊送球

作者单位： 中国科学院大连化学物理研究所

项目金额： 25万元

中文摘要： 核酸DNA和RNA对紫外光有很强的吸收，从而产生电子激发态，这可能会引发导致DNA和RNA光损伤的光化学反应。嘧啶碱基是生物体核酸DNA和RNA中的核心组成单元，也是DNA和RNA中光化学活性较高的分子。目前对嘧啶碱基激发态的研究结果尽管已经证实了亮态1ππ*和基态的势能面其中一个锥形交叉点的大概位置和构型，但是激发态中的暗态1nπ*的非辐射弛豫路径还不清晰，并且对于亮态1ππ*的双指数衰减现象的解释还颇有争议。本项目拟采用在嘧啶碱基单体分子中引入取代基的办法，用以改变嘧啶碱基的激发态能级结构，抑制某些面外振动从而抑制一些非辐射衰减通道。通过对这些嘧啶碱基衍生物的量子化学理论计算将得到激发态的弛豫路径和锥形交叉区域的分子构型等信息，通过稳态光谱和超快瞬态光谱的测量，将得到激发态各电子态的弛豫动力学信息。结合理论与实验，解释亮态双指数衰减现象，阐明嘧啶碱基衍生物激发态的动力学弛豫模型。

中文关键词： 生物碱基；光损伤；分子激发态；超快光谱；激发态动力学

英文摘要： Ultraviolet light is strongly absorbed by nucleic acid, DNA and RNA, producing excited electronic states that sometimes initiate damaging photochemical reactions. Pyrimidine bases are one of the core of DNA and RNA, which frequently show high photochemical reactivity. The studies on pyrimidine bases have shown one of the conical intersection (CI) between the bright state 1ππ* and ground state, and elucidated this decay path of the bright state. But the decay dynamics of the dark state, such as 1nπ*, in pyrimidine bases are still unclear, and there are debates on the understanding of the bi-exponential decay of the bright state. This project will introduce some substitutes to pyrimidine bases to change the energy level of excited electronic states, or to constrain the out-of-plane vibration, subsequently, change the irradiation decay paths. The quantum chemical calculations will be done to obtain the decay paths of excited electronic states and the geometries at CIs. The excited state dynamics can be obtained by using steady state and ultrafast transient spectroscopy. According to the theoretical and experimental results, we may give a clear understanding on the bi-exponential decay of the bright state, and elucidate the excited-state decay paths of pyrimidine bases derivatives.

英文关键词： nature bases；photodamage；molecular excited state；ultrafast spectroscopy；excited state dynamics