The interaction of carboxylate ions (acetate, butyrate) with nucleic aicd bases and nucleosides has been investigated by proton magnetic resonance in dimethyl sulfoxide (d6)/H2O mixtures. Carboxylate ions interacted only with guanine derivatives and led to a large downfield shift of the NH2 resonance. A 1:1 stoichiometry was deduced from a study of the concentration dependence of chemical shifts. A study of substituted guanine showed that hydrogen bonding involved N(1)H and NH2(2). An association constant of 110 M-1 was determined. This value is about 30 times higher than the association constant for guanine-cytosine base pair formation under the same experimental conditions. As a matter of fact, carboxylate ions induced a dissociation of guanine-cytosine base pairs. This guanine-carboxylate association is experimental evidence for a highly specific interaction that could play an important role in protein/nucleic acid recognition.
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Lancelot et al. (1977) studied this question.