Phosphate- N base hydrogen bonds involving proton transfer with reference to the non-enzymic hydrolysis of ATP

IR spectra of aqueous solutions of 1:1 mixtures of H₂PO₄^? and various N bases have been studied as models for (POH?N) → (P^?O?H⁺N) hydrogen bonds. 50% proton transfer is observed when the pKa of the protonated N base is 1.1 smaller than that of the phosphate group. The hydrogen bonds are easily polarizable near this equilibrium. These results strongly support the conclusion that such bonds contribute 1) to the self-association of ATP and ADP and 2) to the association of the hydrolysis products ADP and inorganic phosphate.