Abstract: Epigenetic modification of nucleic acid plays a vital role in realizing the epigenetic functions in living organisms. It can participate the regulation of cell differentiation, gene expression and other important physiological processes. However, epigenetic modification may undermine the photostability of nucleic acid, which may turn the corresponding nucleobases into important mutation sites for diseases such as skin cancer. Therefore, it is of great significance to study the effect of epigenetic modification on the photophysical and photochemical properties of nucleobases. In this paper, we reviewed recent research progress on the excited state dynamics of a series of epigenetic modified nucleobases. With the help of femtosecond time-resolved spectroscopy and high level quantum chemistry calculations, we demonstrated that the effect of epigenetic modification on the excited state properties of nucleobases are mainly in three aspects: significantly increasing the lifetime of the bright ππ∗1 states, introducing intramolecular charge transfer states and effectively promoting intersystem crossing from singlet to triplet states.

Key words: epigenetics, nucleobase, ultrafast spectrscopy, excited state dynamics