Complex formation of carnosine with purine nucleotides in aqueous solution.

This 1H-NMR study provides experimental evidence for an intermolecular interaction between the dipeptide carnosine (beta-alanyl-L-histidine) and the purine nucleoside 5'-monophosphates 5'-AMP, 5'-GMP. From the observed upfield shifts of the purine nucleotide and imidazole proton resonances it is concluded that the interaction is of the stacking type and that it involves the purine base of the nucleotide and the histidine moiety of carnosine. Apparent microscopic equilibrium constants and complex shifts are obtained with a microscopic model which considers the formation of both 1:1 and 1:2 complexes. The stacking pattern for complex formation between the histidine moiety of carnosine and the adenine moiety of 5'-AMP is constructed by fitting the experimental 5'-AMP complex shifts to the calculated isoshielding contours for histidine.