Effect of the Alkali-Metal Cations On the Protonation Constants of Myo-Inositol Hexakis(Phosphate)

Abstract
Values for the protonation constants of myo-inositol hexakis(phosphate) have been determined at 25°C and 0.1 M ionic strength by potentiometry in media containing two different concentrations of Li+, Na+, K+ and Cs+ salts. The Alog KyHM values, which correspond to the differences between the constants obtained with and without alkali-metal cations, are considered as being related to the binding ability of the ligand towards these cations. Their relative behaviour is then analysed and some conclusions are drawn about the conformations which might be adopted by the complexes in different pH regions.