FORMATION OF 5-HYDROXY-5,6-DIHYDROURACIL AND RELEASE OF UNDAMAGED URACIL AS A RESULT OF POLY(U) IRRADIATION IN N2O-SATURATED AQUEOUS-SOLUTION

The radiation chemical yields of 5-hydroxy-5,6-dihydrouracil and uraci l were measured on radiolysis of N2O-saturated solutions containing 1 mmol dm(-3) poly(U) and were found to be 0.04 and 0.31 mu mol J(-1) re spectively. From the 5-hydroxy-5,6-dihydrouracil yield in the presence of cysteamine and 2-mercaptoethanol, it is shown that only 20% of the OH-radicals, which attack poly(U) results in the formation of 5-hydro xy uracil adducts. It has been proposed that as yet unknown reducing r adicals are formed in addition to known reducing radicals (the 5-OH-ad ducts of uracil, the H-adducts of uracil, and sugar radicals) as a res ult of the reaction of OH-radicals with poly(U).