ACID-CATALYZED DEPURINATION OF DIDEOXYRIBONUCLEOTIDES, TRIDEOXYRIBONUCLEOTIDES AND POLYDEOXYRIBONUCLEOTIDES - EFFECT OF MOLECULAR ENVIRONMENT ON THE CLEAVAGE OF ADENINE RESIDUE

First-order rate constants for the acid-catalysed cleavage of adenine base from 2'-deoxyadenosine, its 3'- and 5'-monophosphates, various dinucleoside monophosphates, trinucleoside diphosphates and hexameric 2'-deoxyadenylic acid were measured by the method of initial velocity. The results obtained were compared with the effect that heteroassociation with caffeine has on the pre-equilibrium protonation and rate-limiting heterolysis of 2'-deoxyadenosine and its isosteric analogue, 1-(2-deoxy-beta-D-erythro-pentofuranosyl)benzimidazole. The kinetics of the depurination of poly(dA-T), poly(dA) and a mixture of poly(dA) and poly(T) were determined, and the rate variations observed are discussed on the basis of the known structures of these polymers.