Generation of abasic sites in DNA by singlet oxygen produced from a photocatalytic reaction

Stress factors such as photoreaction and inflammation are known to damage nucleic acids in various ways. Guanine, among the four canonical nucleobases, is particularly susceptible to oxidation, leading to the formation of oxidative lesions such as 8-oxoguanine, spiroiminodihydantoin, and guanidinohydantoin. In this study, we now report an abasic (AP) site generation from guanine residue oxidation based on photocatalytic reactions. The study used Dickerson–Drew dodecamer DNA as the model oligo DNA for photocatalytic reactions, and the reactions were analyzed using denaturing polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry measurements. It was observed that guanine residues are converted into AP sites by reacting with singlet oxygen generated from the photocatalyst. Guanine residues with high solvent accessibility were found to be particularly reactive with singlet oxygen. The study further proposes a mechanism for AP site generation, suggesting that further oxidation of 8-peroxy intermediate (8-OOH-G) with singlet oxygen is a crucial step in the process. These findings are important for the design and development of photocatalyst-modified functional oligo probes and the understanding of their reactions.