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Abstract
As a step towards elucidating the mechanisms of mutagenesis induced by irradiation and oxidation, we study the incorporation of 8-oxoguanine (OG) into duplex DNA. Molecular modelling is used to reveal changes in DNA conformational parameters due to mispairs within the sequences d(A5XA5) · d(T5YT5) and d(G5XG5) · d(C5YC5) where one of the bases of the bases of the central X:Y pair is OG and the other A T, G or C. The G:C to OG:C replacements in DNA duplexes produce only minor conformational changes, similar to normal base sequence effects. The calculations suggest that both OG(syn): G and OG(syn): A mispairs can also be introduced without drastic distortion of sugar-phosphate backbone. The distortions produced by OG-containing mispairs are also found to be sequence dependent Overall these calculations suggest that the G→OG conversion could be an important factor in the irradiative or oxidative damage of DNA.