物理化学学报 >> 2011, Vol. 27 >> Issue (11): 2559-2564.doi: 10.3866/PKU.WHXB20111115

理论与计算化学 上一篇    下一篇

堆积的胸腺嘧啶体系光物理失活的动力学模拟

豆育升, 李伟, 袁帅, 张文英, 李安阳, 舒坤贤, 唐红   

  1. 重庆邮电大学高性能计算与应用研究所, 重庆 400065
  • 收稿日期:2011-05-24 修回日期:2011-07-26 发布日期:2011-10-27
  • 通讯作者: 豆育升 E-mail:douys@cqupt.edu.cn
  • 基金资助:

    国家自然科学基金(21073242), 重庆市自然科学基金(cstc2011jjA00009)和重庆市教委科学技术项目(KJ100507)资助

Dynamics Simulation of Photophysical Deactivation Pathway for Stacked Thymines

DOU Yu-Sheng, LI Wei, YUAN Shuai, ZHANG Wen-Ying, LI An-Yang, SHU Kun-Xian, TANG Hong   

  1. Institute of High Performance Computing and Application, Research Center of Network and Computing, Chongqing University of Posts and Telecommunications, Chongqing 400065, P. R. China
  • Received:2011-05-24 Revised:2011-07-26 Published:2011-10-27
  • Contact: DOU Yu-Sheng E-mail:douys@cqupt.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21073242), Natural Science Foundation of Chongqing, China (cstc2011jjA00009) and Project of the Science Technology Foundation of Chongqing Education Committee, China (KJ100507).

摘要: 采用半经典动力学方法模拟了π堆积的胸腺嘧啶体系最低激发态的光物理失活过程. 设置激光脉冲仅作用于一个胸腺嘧啶分子T, 另一胸腺嘧啶分子T′保持基态. 模拟发现由于T与T′之间存在π堆积相互作用, 导致电荷转移, 形成T带负电荷、T′带正电荷的激基复合物. 由于相邻分子的空间效应阻碍了激发的T分子到达圆锥相交所必需的强烈扭曲, 激基复合物的寿命比单体增长. 当分子间距离缩短至0.3 nm后, T分子C5―C6键扭曲程度最大, 此时发生电荷重组, 两个胸腺嘧啶分子均恢复电中性. 电荷重组诱导T′分子发生畸变, 并在C5′―C6′扭曲最大时避免相交, 体系衰减至基态, T和T′分子均恢复平面构型.

关键词: 胸腺嘧啶, 半经典动力学模拟, 电荷转移, 激基复合物, 失活

Abstract: A semiclassical dynamics simulation study was undertaken to determine the photophysical deactivation of the lowest excited state of two stacked thymines. Only one thymine, referred to as T, was excited by a laser pulse and the other molecule, referred to as T′, remained in the ground state. The simulation results show that charge transfer between the two thymines because of a π-stacking interaction leads to the formation of an excimer state, which includes a negative T and a positive T′. Additionally, the simulation study indicates that a steric effect of the neighboring bases inhibits the out-of-plane deformation, which is essential in accessing the conical intersection between the lowest electronic-excited state and the ground state. The steric effect eventually leads to a longer electronic-excited state lifetime for the two stacked thymines. The simulation results reveal that when the interbase distance is less than 0.3 nm the molecule T has a remarkable deformation at its C5 and C6 sites resulting in charge recombination. The charge recombination ultimately makes the system electronically neutral. On the other hand, the molecule T′ has a strong twist about its C5′―C6′ bond in the proximity of the avoided crossing by which the system decays to the ground state. Finally, the two thymine molecules in their ground states recover their planar geometries.

Key words: Thymine, Semiclassical dynamic simulation, Charge transfer, Excimer, Deactivation

MSC2000: 

  • O641