高等学校化学学报 ›› 2021, Vol. 42 ›› Issue (7): 2136.doi: 10.7503/cjcu20210117

• 研究论文 • 上一篇    下一篇

DNA环境中硒代胸腺嘧啶和腺嘌呤碱基对的激发态性质和光物理机理的理论研究

彭沁, 方业广, 张腾烁, 崔刚龙(), 方维海()   

  1. 北京师范大学化学学院, 理论及计算光化学教育部重点实验室, 北京 100875
  • 收稿日期:2021-02-26 出版日期:2021-07-10 发布日期:2021-06-03
  • 通讯作者: 崔刚龙 E-mail:ganglong.cui@bnu.edu.cn;fangwh@bnu.edu.cn
  • 作者简介:方维海, 男, 博士, 教授, 中国科学院院士, 主要从事非绝热动力学方法发展及其应用研究. E-mail: fangwh@bnu.edu.cn
  • 基金资助:
    国家自然科学基金(21688102)

Theoretical Study on the Excited State Properties and Photophysical Mechanism of Selenothymine and Adenine Base Pairs in DNA Environment

PENG Qin, FANG Yeguang, ZHANG Tengshuo, CUI Ganglong(), FANG Weihai()   

  1. Key Laboratory of Theoretical and Computational Photochemistry,Ministry of Education,College of Chemistry,Beijing Normal University,Beijing 100875,China
  • Received:2021-02-26 Online:2021-07-10 Published:2021-06-03
  • Contact: CUI Ganglong E-mail:ganglong.cui@bnu.edu.cn;fangwh@bnu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21688102)

摘要:

应用高精度的多态完全活化自洽场二级微扰理论方法, 在量子力学/分子力学组合方法的理论框架 QM(MS-CASPT2//CASSCF)/MM下, 系统研究了DNA环境中2-硒和4-硒取代胸腺嘧啶和腺嘌呤碱基对(2SeT-A和4SeT-A)的最低5个电子态(S0, S1, S2, T2和T1)的结构、 性质和光物理过程. QM(MS-CASPT2//CASSCF)/MM计算揭示了DNA环境中2SeT-A和4SeT-A碱基对激发态性质和光物理过程差异性的来源, 提出的机理将有助于理解DNA类似物的光物理过程, 在光动力学治疗中具有潜在的应用.

关键词: 硒代碱基, QM/MM, 激发态性质, 光物理, MS-CASPT2

Abstract:

Multi-state second-order perturbation approach was applied, the combination of quantum mecha-nics/molecular mechanics methods, under the theoretical framework of the QM(MS-CASPT2//CASSCF)/MM, to study the relevant minima, conical intersections, crossing points, and excited-state relaxation paths in the lowest five electronic states(i.e., S0, S1, S2, T2, and T1) of 2- and 4-selenothymine and adenine bases(2SeT-A and 4SeT-A) in DNA. Although 2SeT-A and 4SeT-A share similar electron excitation states, their electron structural characteristics are different due to the different n and π orbitals involved, resulting in a higher vertical and adiabatic excitation energy for 2SeT-A than for 4SeT-A. In addition, both 2SeT-A and 4SeT-A have different minimum energy structures and inactivation pathways in the DNA environment. For 2SeT-A, after excitation, the system first reaches the S2(ππ*) state in the Franck-Condon region, then relaxes to the S2 state minimal energy structure, and finally to the S1nπ*) state. Next, the S1→T1 process with a large S1/T1 spin-orbit coupling reaches the T1(ππ*) state, which can be arrived to the S0 state again through the T1/S0 intersection. But the minimum energy structure of T1 and the barrier of 22.6 kJ/mol between T1/S0 intersection make the system stay in the lowest T1 triplet state for a period of time. 4SeT-A has similar photophysical process of S2→S1→T1, but its S2→S1 internal transformation process needs to overcome the energy barrier of 60.7 kJ/mol. The results reveals the different sources of the excitation state properties and photophysical mechanisms of 2SeT-A and 4SeT-A base pairs in DNA environment, and provides insight into the mechanism, which will help to understand the excitation state properties and photophysical mechanisms of bases substi- tuted by selenium atoms in complex environment.

Key words: Selenothymine, QM/MM, Excitation state property, Photophysics, MS-CASPT2

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