The formation of mispairs by 8-oxyguanine as a pathway of mutations induced by irradiation and oxygen radicals.

Guanine conversion to 8-oxyguanine (OG) was induced by irradiation and oxygen radicals. The pathways of mutations caused by such DNA damage have been considered. Minima of interaction energies of OG with nucleic acid bases are revealed via classical potential function calculations. The minima exist for OG*:G and OG*:A base pairs, with syn-conformation of OG* and OG:T wobble base pairs. The mutual positions of glycosyl bonds in these base pairs are quite close to those for Watson-Crick pairs, and energies of OG*:G, OG*:A and OG:T mispairs are close to the energy of A:T. The results calculated suggest that these mispairs could arise as intermediates in the transversions C:G to G:C and C:G to A:T, and the transition G:C to A:T.