[{"from": "human", "value": "What can you tell me about this molecule? [C][O][C][=N][C][=Branch1][O][=N][C][=C][Ring1][=Branch1][N][C][=N][Ring1][Branch1][N]"}, {"from": "gpt", "value": "The molecule is a methylguanine in which the methyl group is positioned on the oxygen at position 6. Formed in DNA by alkylation of the oxygen atom of guanine, most often by N-nitroso compounds and sometimes due to methylation by other compounds such as endogenous S-adenosylmethionine, it base-pairs to thymine rather than cytidine, causing a G:C to A:T transition in DNA. It has a role as a mutagen."}]