The thermodynamic parameters of step dissociation of D,L-α-alanyl-D,L-valine in aqueous solutions

The heats of interaction between D,L-alpha-alanyl-D,L-valine and solutions of nitric acid and potassium hydroxide were determined calorimetrically at 288.15, 298.15, and 308.15 K and solution ionic strengths of 0.5, 1.0, and 1.5 in the presence of KNO3 and LiNO3. The heat effects of peptide dissociation were calculated using the universal RRSU program. The standard thermodynamic characteristics (Delta(r)H(o), Delta(r)G(o), Delta(r)S(o), and DeltaC(p)(o)) of proton interaction with the peptide were determined. The suggestion was made that the peptide zwitterion was hydrated more strongly than the zwitterion of the corresponding amino acid.