5-Formyldeoxyuridine: a new type of DNA damage induced by ionizing radiation and its mutagenicity to salmonella strain TA102.

An aqueous solution of calf thymus DNA was irradiated by 60Co γ-rays and modified nucleosides produced in DNA were analyzed by high-pressure liquid chromatography coupled with a photodiode array UV detector. A new product with UV absorption maxima at 230 nm and 280 nm was observed. The structure of this compound was proposed to be 5-formyldeoxyuridine (f5dU) based on the mass spectrum of its trimethylsilyl derivative (M+, m/z 472) and the structure was confirmed by chemical synthesis. The yield of f5dU (2.4104dT/krad) in DNA was of roughly the same order as that of 8-hydroxydeoxyguanosine and 5-hydroxymethyldeoxyuridine. Free f5dU was mutagenic to Salmonella typhimurium strain TA102: therefore f5dU incorporated into DNA may induce mutations.