Nuclear magnetic resonance studies on the self-association of adenosine 5′-triphosphate in aqueous solutions

The self-association of adenosine 5′-triphosphate (ATP) in aqueous, basic solutions has been studied. The results indicate that the monomer–dimer–trimer equilibrium model for base association fits the data well, but so does a model which includes higher order species. This indicates that the ATP molecules in solution can undergo indefinite linear self-association. The average value of the association constant based on the 1H and 31P chemical shift measurements is 0.9 ± 0.3 M−1. Longitudinal relaxation rates for the H8, H1′, and H2 protons of ATP were obtained as a function of the nucleotide concentration. The analysis of the viscosity-corrected proton H2 data yields an association constant of 5.1 ± 1.3 M−1.