Thermodynamic quantities for the dissociation equilibria of biologically important compounds. 6. The dissociation of calcium glucose 1-phosphate

Abstract

There is considerable evidence that the calcium salts of many multivalent acids are incompletely dissociated in solution (Martell & Calvin, 1952); among others the dissociation constant of calcium hydrogen phosphate has been measured (Greenwald, Redish & Kibrick, 1940; Davies & Hoyle, 1953). Since glucose 1-phosphate (G1-P) is known to occur in calcifying cartilage (see, for example, McLean & Urist, 1955) it is of interest to obtain detailed information about any interactions between its anions and Ca2+ ions. The titration curves of K2G1-P with hydrochloric acid in the presence of sodium chloride or calcium chloride of equal ionic strength (Fig. 1) show that Ca2+ ions interact with the species G1_P2but not with HG1-PW. These findings are similar to those with Mg2+ ions and G1-P (Clarke, Cusworth & Datta, 1954). It has therefore been assumed that the only complex formed in significant amounts is CaGl-P and the possibility that complexes such as CaHG1-P+ or Ca(HG1-P)2 were formed has been ignored. Accordingly, 11 G1-P buffers containing calcium chloride were examined potentiometrically in cells without liquid junction of the type Pt.H2 (1 atm.) KHG1-P (mna).K2GL-P (fn). CaCl2 (mn8) AgCl. Ag at 100, 200, 300, 40°and 50°. From the e.m.f. of these cells, together with the values of ina, nib and mns, the dissociation constant of CaGl-P Ks K acs+aGl-p2 (1) was calculated by the method used for the magnesium salt (Clarke et al. 1954). The values oflog K8 at different temperatures were found to vary according to the Harned & Robinson (1940) equation-log K,=A/T-D+CT,

Uranium(VI) complexes with sugar phosphates in aqueous solution

“…Many studies about the complexation behavior of various metal ions with sugar phosphates have been published [5][6][7][8][9][10][11][12][13][14]. The first investigation of complex formation with actinides was the reaction of glucose 1-phosphate with uranium(VI) [15].…”

“…The first investigation of complex formation with actinides was the reaction of glucose 1-phosphate with uranium(VI) [15]. Former studies with simple metal(II) cations describe only complexes with a metal-to-ligand ratio of 1 : 1 [5][6][7][8][9][10][11][12][13][14]. Uranium(VI) forms additionally a 1 : 2 complex [15].…”

Thermodynamic quantities for the dissociation equilibria of biologically important compounds. 7. The second acid dissociation of glycerol 1-phosphate

“…Twelve diluted solutions were made from each stock solution, the ionic strengths being from 0-02 to 0 09. * Part 6: Clarke & Datta (1956).…”