| Popis: |
The protonation and the complexation properties of the D- myo -inositol 1,2,6-trisphosphate (Ins(1,2,6)P 3 ) towards calcium and magnesium were studied in two different media and temperature conditions. The results obtained in a 0.1 M tetra-n-butylammonium bromide solution, at 25°C, account for the “intrinsic” complexation ability of the ligand, whereas in a 0.2 M KCl medium at 37°C, the results enable the influence of the presence of alkali cations to be considered. Comparison of the protonation constants obtained in both media clearly shows the competition between the weak acidic protons of the phosphate groups and the potassium ions. Due to the high number of negative charges carried by the ligand over a large p H range, various species which include mononuclear, polynuclear and protonated complexes were found. The relative stability of these complexes is discussed, and illustrated by their species distribution curves versus p H . |
