PATTERN OF OH RADICAL REACTION WITH ADENINE AND ITS NUCLEOSIDES AND NUCLEOTIDES - CHARACTERIZATION OF 2 TYPES OF ISOMERIC OH ADDUCT AND THEIR UNIMOLECULAR TRANSFORMATION REACTIONS

The ⋆OH radical reacts in aqueous solution with adenine, 9-methyladenine, adenosine and its 3′- and 5′-mono- and 3′,5′-diphosphates, and with the corresponding 2′-deoxyadenosines by addition to C4 and to C8 of the purine system. The resulting hydroxycyclohexaor penta(aza)dienyl-type radicals A4OH⋆ (formed by ⋆OH addition at C4) and A8OH⋆ (by addition at C8) undergo a dehydration and a ring-opening reaction, respectively, for which the activation parameters and pH dependencies have been determined. Dehydration of A4OH⋆, which yields an oxidizing N6-centered neutral radical, is inhibited by H+, whereas the ring opening of A8OH⋆ is accelerated by H+ (and also by OH-). Product analysis data on adenine concerning the effect of additives on the yield of its depletion and of formation of 8-hydroxyadenine indicate that the N6-centered radical is repaired by reduction by radicals derived from A8OH⋆. © 1990, American Chemical Society. All rights reserved.