REACTION OF PURINES WITH HYDROXYL RADICAL GENERATED BY PHOTOLYSIS OF MERCAPTOPYRIDINE-N-OXIDES

The UV-photolysis of 4-mercaptopyridine-N-oxyde in aqueous solution is shown to be an efficient method of generating HO. radicals, as an alt ernative to the radiolysis of water. The reaction of adenine with HO. produced by the photolytic method resulted in the formation of 8-hydro xyadenine and 4,6-diamino-5-formamidopyrimidine in conditions and yiel ds similar to those observed when HO. is produced by water radiolysis. ESR studies of the transients formed upon reaction of HO. with xanthi ne showed the formation of a radical anion in neutral conditions and a radical dianion at high pH values, due to the oxidation of the substr ate by the conjugate base of HO., the O.- radical.