Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis. Part I. Transformation reactions of two isomeric OH-adducts.

摘要: The absorption spectra of polyadenylic acid (polyA) radicals in N2O saturated aqueous solution have been measured as a function time (up to 15 s) following an 0.4 microsecond electron pulse. and their changes were analysed by comparison with those from monomeric adenine derivatives (nucleosides nucleotides) which had studied Steenken. reaction OH. the moiety polyA results formation two hydroxyl adducts at positions C-4 [polyA4OH.] C-8 [polyA8OH.]. Each OH-adduct undergoes unimolecular transformation before any bimolecular or other decay occurs. These reactions are characterized different rate constants pH dependencies. polyA4OH. adduct dehydration yield neutral N6 centered radical (rate constant kdeh = 1.4 x 10(4)s-1 7.3). This is strongly inhibited H+. In analogous adenosine phosphates, kinetic pK value for its inhibition units higher. shift result counter ion condensation double-strand formation. polyA8OH. imidazole ring opening enol type formamidopyrimidine resulting base damage (kr.o. 3.5 contrast catalysed H+ OH-, similar but compared nucleotides.