Acta chemica Scandinavica/Acta chemica Scandinavica. B, Organic chemistry and biochemistry/Acta chemica Scandinavica. A, Physical and inorganic chemistry/Acta chemica Scandinavica. Series B. Organic chemistry and biochemistry/Acta chemica Scandinavica. Series A, Physical and inorganic chemistry · 1999 · 44 citations · 0 references
Life SciencesBiochemistryChemistryCarbohydrate BiochemistryCarbohydrate ChemistryInorganic ChemistryBioinorganic ChemistryCalcium MetabolismCalcium-binding ProteinsPolysaccharide FunctionPolysaccharide StructureCalcium Biochemistry
The complexation of Ca<sup>2+</sup> by α-isosaccharinic acid (α-ISA) was determined by measuring the solubility of Ca(α-ISA)<sub>2</sub> as a function of pH. In the pH range between 12 and 12.8, the observed increase of the total concentration of Ca in solution with increasing pH is explained by the complexation reaction:<br /><br /> Ca<sup>2+</sup> + α-ISA<sup>–</sup> ⇋ Ca(α-ISA<sub>–H</sub>)<sup>0</sup> + H<sup>+</sup><br /><br /> with log <em>K</em>°<sub>CaISA<sup>0</sup></sub> = –10.4 (<em>s</em> = 0.2) at I = 0. In addition to this complexation reaction, another complex is postulated:<br /><br /> Ca<sup>2+</sup> + α-ISA<sup>–</sup> ⇋ Ca(α-ISA)<sup>+</sup><br /><br /> with log <em>K</em>°<sub>CaISA</sub><sup><sub>+</sub></sup>= 1.70. A value for the solubility product of Ca(α-ISA)<sub>2</sub> is calculated: log K°<sub>sol</sub> = –6.36 (<em>s</em> = 0.1) at <em>I</em> = 0.