Theoretical Study of Light-Induced Crosslinking Reaction Between Pyrimidine DNA Bases and Aromatic Amino Acids

Abstract

Low-lying electronic excited states and their relaxation pathways as well as energetics of the crosslinking reaction between uracil as a model system for pyrimidine-type building blocks of DNA and RNA and benzene as a model system for aromatic groups of tyrosine (Tyr) and phenylalanine (Phe) amino acids have been studied in the framework of density functional theory. The equilibrium geometries of the ground and electronic excited states as well as the crossing points between the potential energy surfaces of the uracil–benzene complex were computed. Based on these results, different relaxation pathways of the electronic excited states that lead to either back to the initial geometry configuration or the dimerization between the six-membered rings of the uracil–benzene complex have been identified, and the energetic conditions for their occurrence are discussed. It can be concluded that the DNA–protein crosslinking reaction can be induced by the external electromagnetic field via the dimerization reaction between the six-membered rings of the uracil–benzene pair at the electronic excited-state level of the complex. In the case of the uracil–phenol complex, the configuration of the cyclic adduct (dimerized) conformation is less likely to be formed.

New insight into catechol photochemistry: the role of different monomer and dimer configurations in radiation-less decay of the S1electronic excited state

“…In our previous study, 64 it was proved that not only monomers can show exclusively CI-type geometric deformations ( e.g. , half-boat-like distortion of the benzene ring), but also CI-type configurations can be formed by involving two molecules.…”

“…In our previous study 62 , it was proved that not only monomers can show exclusively CI-type geometric deformations (e.g., half-boat-like distortion of the benzene ring), but also CI-type congurations can be formed by involving two molecules. In the latter case, both molecules present signicant geometric distortions and new, weaker covalent bonds may be formed between the atoms of the two molecules.…”

“…These energy differences come from both the weaker intermolecular interaction between the monomers and the deformation energy found for the CI M geometries of the isolated monomers compared to R c e (S 1 ). In our previous study, 64 it was proved that not only monomers can show exclusively CI-type geometric deformations (e.g., half-boat-like distortion of the benzene ring), but also CI-type configurations can be formed by involving two molecules. In the latter case, both molecules present significant geometric distortions and new, weaker covalent bonds may be formed between the atoms of the two molecules.…”