scholarly journals The equilibrium constant of the phosphoglyceromutase reaction

1974 ◽  
Vol 139 (3) ◽  
pp. 491-497 ◽  
Author(s):  
John B. Clarke ◽  
Michael Birch ◽  
Hubert G. Britton
Keyword(s):  
Ionic Strength ◽  
Equilibrium Constant ◽  
Dissociation Constants ◽  
Ph Dependence ◽  
Binding Constants ◽  
Acid Dissociation ◽  
Effect Of Temperature ◽  
Acid Dissociation Constants ◽  
The Difference ◽  
Low Ionic Strength

The equilibrium constant of the phosphoglyceromutase reaction was determined over a range of pH (5.4–7.9), in solutions of different ionic strength (0.06–0.3) and in the presence of Mg2+, at 30°C and at 20°C. The values obtained (8.65–11.65) differ substantially from previously published values. The third acid dissociation constants were redetermined for 2- and 3-phosphoglycerate, and in contrast with previous reports the pK values (7.03 and 6.97 respectively at zero ionic strength) were closely similar. The Mg2+-binding constants were measured spectrophotometrically and the values, 286mm-1 and 255mm-1 for 2- and 3-phosphoglycerate at pH7 and ionic strength 0.02, were also very similar. From the relative lack of effect of temperature, pH and ionic strength it is concluded that the equilibrium constant differs from unity largely because of entropic factors. At low ionic strength, in the neutral region, the pH-dependence can be attributed to the small difference in the acid dissociation constants, but the difference in dissociation constants does not explain the pH-dependence in the acid region or at high ionic strength. Within physiological ranges of pH, Mg2+ concentration and ionic strength there will be little variation in equilibrium constant.

The comparative chemistry of ammine and methylamine complexes of rhodium(III) and cobalt(III)

1977 ◽  
Vol 55 (17) ◽  
pp. 3166-3171 ◽  
Author(s):  
Thomas Wilson Swaddle
Keyword(s):  
Ionic Strength ◽  
Spectral Data ◽  
Electron Donor ◽  
Dissociation Constants ◽  
Base Hydrolysis ◽  
Acid Dissociation ◽  
Rate Coefficients ◽  
Acid Dissociation Constants ◽  
First Order ◽  
Kinetics Of

For the aquation of (CH3NH2)5RhCl2+, the first order rate coefficients are represented by ΔHaq* = 101.9 kJ mol−1 and ΔSaq* = −50.2 JK−1 mol−1 in 0.1 M HClO4, while for base hydrolysis the rate is first order in [(CH3NH2)5RhCl2+] and [OH−] at ionic strength 0.10 M and the rate coefficients (in M−1 s−1) are represented by ΔHOH*> = 108.6 kJ mol−1 and ΔSOH* = 74.1 J K−1 mol−1. Acid dissociation constants are reported for (RNH2)5MOH23+ (R = H or CH3; M = Rh or Co), and these, combined with spectral data, show CH3NH2 to be a poorer electron donor than NH3 in complexes of this type, contrary to expectations. The comparative kinetics of reactions of (RNH2)5MCl2+ support the assignment of an Ia mechanism to aquation when M = Rh or Cr, Id to aquation when M = Co, and Dcb for base hydrolysis in all these cases.

Pyridine nitrosazones and their cobalt(III) chelates

1977 ◽  
Vol 55 (21) ◽  
pp. 3707-3711 ◽  
Author(s):  
Ahmad Sami Shawali ◽  
Ikhlass M. Abbass
Keyword(s):  
Ionic Strength ◽  
Spectral Data ◽  
Dissociation Constants ◽  
Ring Structure ◽  
Membered Ring ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Transition Energies ◽  
Amyl Nitrite ◽  
Good Agreement

Nitrosation of pyridine aldehyde p-tolylhydrazones 2 with amyl nitrite gives rise to p-tolueneazopyridine aldoximes 4 which form stable tris chelates with cobalt(III). Spectral data (ir, uv, and 1Hmr) indicate that the ligands exist mainly in the assigned azooxime structure 4, and that their chelates have five-membered ring structure 7. Also, the 1Hmr spectra imply mer-configuration 9 for the chelates examined. No evidence for the tautomeric nitrosohydrazone structure 3 for the ligands and the fac-configuration 8 for Co(III) chelates could be obtained. Using the HMO method, the azooxime form 4 for the ligand was shown to be more stable than the nitrosohydrazone structure 3. Also, good agreement was obtained between observed transition energies and those calculated by the HMO method. The acid dissociation constants of the ligands in 50 vol% ethanol–water at 25 °C and ionic strength of 0.1 were determined spectrophotometrically.

Nuclear magnetic resonance studies of the acid–base chemistry of amino acids and peptides. III. Determination of the microscopic and macroscopic acid dissociation constants of α,ω-diaminocarboxylic acids

1976 ◽  
Vol 54 (21) ◽  
pp. 3392-3400 ◽  
Author(s):  
Thomas L. Sayer ◽  
Dallas L. Rabenstein
Keyword(s):  
Chemical Shift ◽  
Dissociation Constants ◽  
Nonlinear Least Squares ◽  
Acid Dissociation ◽  
Acid Base ◽  
Acid Dissociation Constants ◽  
Ammonium Group ◽  
Titration Curves ◽  
Chemical Shift Titration ◽  
The Difference

The acid–base chemistry of 2,3-diaminopropionic acid (dap), 2,4-diaminobutyric acid (dab), ornithine (orn), and lysine (lys) has been studied by 13C and proton nmr spectroscopy. Macroscopic acid dissociation constants for titration of the two ammonium groups of each molecule have been calculated from the 13C chemical shift titration curves for the alkyl carbon atoms by nonlinear least squares curve fitting methods. Microscopic acid dissociation constants for the simultaneous titration of the two ammonium groups of protonated orn and lys have been obtained from their proton chemical shift titration curves and from the 13C titration curves for orn and dap. The results indicate that the α-ammonium group of each of these α,ω-diaminocarboxylic acids is more acidic than its ω-ammonium group, but that the difference decreases as the number of carbons separating the ammonium groups decreases so that the acidities of the two ammonium groups of dap are almost identical. Results of pmr studies of the acid–base chemistry of glycyl-L-lysine and L-lysylglycine also are reported.

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