Thermodynamics of Stepwise Dissociation of Glycyl-L-aspartic and Glycyl-L-glutamic Acids

The thermal effects of the protolytic equilibria of glycyl-L-aspartic and glycyl-L-glutamic acids at 298.15 K and ionic strength values of 0.1, 0.3, 0.5, 1.0, and 1.5 (KNO3) were determined by direct calorimetry. Using the results of thermochemical and potentiometric studies performed under identical experimental conditions, the standard thermodynamic characteristics (pK°, ΔdisG°, ΔdisH°, ΔdisS°) of the stepwise dissociation reactions of these dipeptides were calculated. The results are compared with the corresponding data on related compounds.