Formation of 5-hydroxy-5,6-dihydrothymidine and cis-5,6-dihydroxy-5,6-dihydrothymidine in the radiolysis of N2O-Saturated aqueous solutions of thymidine, thymidine 5 '-monophosphate, and DNA

The yields of formation of 5-hydroxy-5,6-dihydrothymidine and cis-5,6-dihyd roxy-5,6-dihydrothymidine in the radiolysis of thymidine, thymidine 5'-mono phosphate, and DNA in N2O-saturated aqueous solutions were measured in orde r to study the mechanism of nucleic acid radiolysis. The above compounds we re found to be main radiolysis products upon irradiation of thymidine and t hymidine 5'-monophosphate. However, these compounds were formed in very low yields upon irradiation of DNA, and they amounted to less than 2% of the d egradation yield of DNA thymine. The yield of the 5-hydroxythymidin-6-yl ra dical was evaluated by determining the amount of 5-hydroxy-5,6-dihydrothymi dine formed in the radiolysis of the above compounds in the presence of cys teamine.