Computational Studies of the Photophysics and Photochemistry of Nucleic Acid Constituents

Nucleic acids consist of nucleobases characterized by unique structures crucial for maintaining their genomic functions and overall structure. This includes a conjugated π-system, a key element supporting the helical structure of double-helix DNA through π–π interactions. Despite this advantageous structural feature, the presence of π-electrons in organic molecules inevitably results in a bathochromic shift in their electronic absorption spectra compared to their saturated counterparts. Consequently, nucleobases may absorb wavelengths that penetrate Earth’s atmosphere, leading to electronic excitations that promote nucleic acid damage and potential cancer. Computational chemistry has proven indispensable in complementing experimental observations and elucidating the active mechanisms through which nucleic acid constituents manage the energy afforded from electronic excitation. A variety of computational methods, spanning static electronic structure calculations to multi- and full-dimensional molecular dynamics simulations, have been employed to offer accurate insights into the photophysics and photochemistry of active excited states in nucleic acid constituents. This chapter provides an overview of some widely used computational approaches for unraveling the fate of excited states in nucleic acid constituents, along with a review of how computational chemistry has revealed the active chemical mechanisms and dynamics involved in photoexcited nucleic acid constituents.