[Self-association of 5'-GMP: nucelation by potassium ions]

23Na and 39K nuclear magnetic resonance are used to follow the self-assocation of 5'-GMP in aqueous solutions. For a 0,1 M concentration in 5'-GMP, large aggregates are formed only in presence of the potassium ion, at greater than 0.2 M concentrations. They do not appear with the other alkali metal cations. A plausible explantation is inclusion of the cation in the central cavity of 5'-GMP tetramers, with a marked selectivity in favor of potassium.