Study of solvent effects on the acid–base behaviour of adenine, adenosine 3′,5′-cyclic monophosphate and poly(adenylic) acid in acetonitrile–water mixtures using hard-modelling and soft-modelling approaches Original Research Article

The acid–base behaviour of adenine, adenosine 3′,5′-cyclic monophosphate and poly(adenylic) acid was studied at 37 °C by spectrometric titration in acetonitrile–water mixtures. Hard-modelling and soft-modelling approaches were used for this purpose. The first one, which requires the assumption of a previous chemical model, was used for the study of monomeric compounds and the second one, an alternating least-squares multivariate curve resolution procedure, was used for the study of poly(adenylic) acid, because it does not require any previous chemical model. The pKa values were correlated with either macroscopic or microscopic parameters, such as solvatochromic parameters. The influence of solvent composition on the intramolecular and solute/solvent interactions such as base stacking and hydrogen-bonding, affects the structure, solubility and the number of species detected.