Formation of 8-hydroxyguanine residues in DNA by X-irradiation

A new type of ionizing radiation-induced DNA base damage, 8-hydroxyguanine formation, was found in DNA that had been irradiated by X-rays in aqueous solution. The extent of this modification linearly increased with increase in the X-ray dose up to 40 krad. When an OH radical scavenger, ethanol, was added to the DNA solution, the hydroxylation was inhibited almost completely, suggesting that the reaction proceeds via the formation of OH radicals.