Photosensitized oxidation of guanine provides various oxidation products, including 8-oxoguanine (8-oxoG) and imidazolone. Riboflavin (vitamin B2) is known as an effective photosensitizer for oxidation of guanine. Here, we show the user-friendly synthesis and photoreaction of a flavin-linked oligonucleotide
the practical synthesis of a hydroxyethyl-flavin (2) from commercially available riboflavin
and the preparation of a flavin-linked oligonucleotide using the phosphoramidite of 2. To demonstrate the usefulness of this method, the flavin-linked oligomer flavin-5'-d(T6CCT6)-3' was synthesized. Flavin-5-d(T6CCT6)-3' and its complementary 5'-d(A6G8-oxoGA6)-3' were irradiated under UV light (366 nm) at neutral pH. Enzymatic digestion of the irradiated mixture with P1 nuclease and alkaline phosphatase indicated that the 8-oxoG residue was oxidized to imidazolone. These results demonstrate that 8-oxoG is effectively oxidized to imidazolone by photosensitization of the terminal flavin via a hole-transfer mechanism, and imidazolone is formed by one-electron oxidation of 8-oxoG at neutral pH. Key words: flavin, 8-oxoguanine, imidazolone, hole transfer, one-electron oxidation. © 2007, The Japanese Environmental Mutagen Society. All rights reserved.