Addition of E−aq and H Atoms to Hypoxanthine and Inosine and the Reactions of α-hydroxyalkyl Radicals with Purines. A Pulse Radiolysis and Product Analysis Study

The reactions of hydrated electrons e−aq with hypoxanthine and inosine were followed using pulse radiolysis methods. In a neutral solution the electron adduct of inosine is immediately protonated at the heteroatoms of the purine ring by water (k ≫ 2·5 × 106s−1) to give In(NO-H)·. These NO-protonated intermediates have a single absorption maximum at 300 nm. In basic solution the protonation of the electron adduct of inosine by water leads to other intermediate products with an absorption maximum at 350 nm. These intermediates are believed to be in C-protonated electron adducts of inosine (In(NO-H)·). In (NO-H)· and In(C-H)· differ strongly in their ability to reduce C-nitroacetophenone (PNAP). In(NO-H)· are strong reductants and reduce PNAP quantitively to PNAP·−. Based on the pH dependence of PNAP·− yields, two types of tautomers of In(C-H)· could be distinguished. One of the tautomers can reduce PNAP, albeit with slower rate than In(NO-H)·, the other tautomer has no reducing properties. The latter is the...