Formation of 5-hydroxy-5,6-dihydrouracil and Release of Undamaged Uracil as a Result of Poly(U) Irradiation in N₂O-saturated Aqueous Solution

Abstract

The radiation chemical yields of 5-hydroxy-5,6-dihydrouracil and uracil 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 μmol J⁻¹ respectively. 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-hydroxy uracil adducts. It has been proposed that as yet unknown reducing radicals are formed in addition to known reducing radicals (the 5-OH-adducts of uracil, the H-adducts of uracil, and sugar radicals) as a result of the reaction of OH-radicals with poly(U).