Characterization of the sodium binding sites in microcrystalline ATP by 23Na-solid-state NMR and ab initio calculations

Abstract Stepwise conformational transition of disodium adenosine 5′-triphosphate (Na 2 ATP) crystals as a function of relative humidity (r.H.), was examined by means of high resolution 23 Na, 31 P solid state NMR spectroscopy and quantum mechanics calculations. 23 Na-MQMAS solid state NMR spectra of hydrated disodium salts of adenosine 5,5′-triphosphate were measured to characterize the individual sodium sites. Quadrupolar coupling constants ( C Q ), and the asymmetry parameters of the electric field gradient tensors ( η ) of sodium-23 determined by quantum mechanical calculations ( gaussian 03) using larger clusters than in previous studies were compared to the experimental 23 Na-MQMAS spectra.