ISOLATION AND CHARACTERIZATION OF A NEW PRODUCT PRODUCED BY IONIZING IRRADIATION AND TYPE-I PHOTOSENSITIZATION OF 2'-DEOXYGUANOSINE IN OXYGEN-SATURATED AQUEOUS-SOLUTION - (2S)-2,5'-ANHYDRO-1-(2'-DEOXY-BETA-D-ERYTHRO-PENTOFURANOSYL)-5-GUANIDINYLIDENE-2-HYDROXY-4-OXOIMIDAZOLIDINE

A major product of the radiation-induced decompostion of 2'-deoxyguanosine in oxygen-saturated aqueous solution has been isolated by reverse phase high performance liquid chromatography and characterized by carbon and proton NMR spectroscopy, fast-atom bombardment mass spectrometry, and chemical analysis as (2S)-2,5'-anhydro-1-(2'-deoxy-beta-D-erythro-pentofuranosyl) -5-guanidinylidene-2-hydroxy-4-oxoimidazolidine(d<G). This compound is stable in aqueous solution at room temperature but decomposes upon heating (45-degrees-C). The lesion is also observed following type I (riboflavin, benzophenone, and acetophenone) photosensitized irradiation of 2'-deoxyguanosine at 350 nm in oxygen-saturated aqueous solution. A similar reaction mechanism, involving a neutral guanine radical intermediate, is proposed to explain the generation of d < G following both types of irradiation.