Ultrafast deactivation channel for thymine dimerization
Ultrafast deactivation channel for thymine dimerization
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DOI：
10.1021/ja073628j
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发表时间：
2007-09-12
影响因子：
15
通讯作者：
Robb, Michael A.
中科院分区：
文献类型：
--
作者：
Boggio-Pasqua, Martial;Groenhof, Gerrit;Robb, Michael A.
链内胸腺嘧啶二聚化是紫外线照射后导致 DNA 光损伤的主要过程。然而，这种光反应背后的机制尚不清楚。在这项研究中，利用高级从头计算在气相中研究了光引发胸腺嘧啶二聚的机制。已进行 CASSCF 和 CASPT2 计算来研究两个堆叠胸腺嘧啶的势能表面。导致诱变胸腺嘧啶二聚体形成的激发态反应途径已被鉴定和表征。中心机械特征是基态和第一激发态之间沿着协同的 [2 + 2] 环加成路径的圆锥形交叉。这种非绝热反应路径解释了超快胸腺嘧啶二聚化的实验观察。
Intrastrand thymine dimerization is the dominant process leading to DNA photodamage after ultraviolet irradiation. However, the mechanism behind this photoreaction is not well understood. In this study, the mechanism for photoincluced thymine dimerization has been investigated in the gas phase using high-level ab initio calculations. CASSCF and CASPT2 calculations have been performed to study the potential energy surfaces of two stacked thymines. The excited-state reaction pathway leading to the formation of the mutagenic thymine dimer has been identified and characterized. The central mechanistic feature is a conical intersection between the ground and first excited states along the concerted [2 + 2] cycloaddition pathway. This nonadiabatic reaction path accounts for the experimental observations on the ultrafast thymine dimerization.