REDOX REACTIONS OF HYDROGEN ADDUCTS OF THYMINE - COMPARISONS WITH THEREACTIONS OF HYDROXYL ADDUCTS

Hydrogen atoms form two kinds of adducts with thymine (oxidizing and r educing). Redox reactions of these two kinds, popularly known as 5-hyd rogenated-6-thyminyl (reducing) and 6-hydrogenated-5-thyminyl (oxidizi ng), were investigated where ferric ions (oxidizing) and ferrous ions (reducing) were used as the corresponding redox partners. A steady-sta te gamma radiolytic system was chosen where hydroxyl radicals were sca venged using t-butyl alcohol in acidic (pH 1.8) solution. It is inferr ed that the redox potential of oxidizing hydrogenated thyminyl radical s lies between 0.77 and 1.4 V as. NHE. The reducing hydrogenated thymi nyl radical has a redox value less than 0.8 V because it efficiently u ndergoes electron transfer reaction with Fe(III). A probable range of redox values for hydroxyl adduct of thymine is included for comparison .