Theoretical studies on photoisomerizations of (6-4) and Dewar photolesions in DNA.
The (6-4) photoproduct ((6-4) PP) is one of the main lesions in UV-induced DNA damage. The (6-4) PP and its valence isomer Dewar photoproduct (Dewar PP) can have a great threat of mutation and cancer but gained much less attention to date. In this study, with density functional theory (DFT) and the complete active space self-consistent field (CASSCF) methods, the photoisomerization processes between the (6-4) PP and the Dewar PP in the gas phase, the aqueous solution, and the photolyase have been carefully examined. Noticeably, the solvent effect is treated with the CASPT2//CASSCF/Amber (QM/MM) method. Our calculations show that the conical intersection (CI) points play a crucial role in the photoisomerization reaction between the (6-4) PP and the Dewar PP in the gas and the aqueous solution. The ultrafast internal conversion between the S(2) ((1)ππ*) and the S(0) states via a distorted intersection point is found to be responsible for the formation of the Dewar PP lesion at 313 nm, as observed experimentally. For the reversed isomeric process, two channels involving the "dark" excited states have been identified. In addition to the above passages, in the photolyase, a new electron-injection isomerization process as an efficient way for the photorepair of the Dewar PP is revealed.
Ai
Yue-Jie
YJ
College of Chemistry, Beijing Normal University, Beijing 100875, China.
Liao
Rong-zhen
RZ
Chen
Shu-feng
SF
Luo
Yi
Y
Fang
Wei-Hai
WH
D004247:DNA / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D004249:DNA Damage; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000378:metabolism; D005740:Gases / Q000737:chemistry; D007536:Isomerism; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D055668:Photochemical Processes; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics
D005740:Gases; D012997:Solvents; D004247:DNA; D004255:Deoxyribodipyrimidine Photo-Lyase