文献类型：期刊文献

英文题名：Ultrafast Intersystem Crossing in Epigenetic DNA Nucleoside 2′-Deoxy-5-formylcytidine

作者：Wang, Xueli[1]; Yu, Yang[2]; Zhou, Zhongneng[1]; Liu, Yangyi[1]; Yang, Youjun[2]; Xu, Jianhua[1,3]; Chen, Jinquan[1,3]

机构：[1] State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062, China; [2] Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, Shanghai, 200237, China; [3] Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, China

年份：2019

卷号：123

期号：27

起止页码：5782

外文期刊名：Journal of Physical Chemistry B

收录：EI(收录号：20192807160043)

语种：英文

外文关键词：Quantum theory - Photosensitizers - Alkylation - Laser spectroscopy - Biomolecules - pH - Excited states - Mammals

摘要：DNA methylation and demethylation are the key steps in epigenetics. Emerging studies have demonstrated that these two processes play crucial roles in mammalian development and pathogenesis. Epigenetic modified cytosine and its further oxidative products, including 5-methylcytosine, 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine, are called the "new four bases of DNA". The appearance of such new epigenetic bases can complicate DNA photodamage and repairing mechanism because they could have drastically different excited-state dynamics compared to canonical DNA nucleobases. In this study, excited-state dynamics of three demethylated nucleosides in buffer solution at physiological pH were investigated by femtosecond to microsecond time-resolved spectroscopy. Distinct excited-state dynamics are found in these demethylated nucleosides. For 2′-deoxy-5-formylcytidine (5fdCyd), direct observation of ultrafast intersystem crossing to the triple state with a 69% quantum yield is presented. Meanwhile, the triplet-state energy of 5fdCyd can transfer to the ambient molecular oxygen and generate destructive singlet oxygen. On the other hand, no such observation is seen in 2′-deoxy-5-hydroxymethylcytidine (5hmdCyd) and 2′-deoxy-5-carboxycytidine (5cadCyd), and these two bases show ultrafast internal conversion similar to that in 5-methylcytidine and cytidine. These results indicate that 5fdCyd is an effective internal triplet photosensitizer in DNA, and it could act as a new hot spot in DNA photodamage. Copyright ? 2019 American Chemical Society.