Densities and heat capacities have been measured for aqueous solutions of L-asparagine, L-glutamine, glycylglycine, glycyl-L-valine, glycyl-L-asparagine, and glycyl-DL-leucine at 288. 15,298.15, 313.15, and 328.15 K. These data have been used to calculate apparent molar volumes, V2,0, and apparent molar heat capacities, Cp,2,0, which in turn have been used to obtain standard state volumes, v;, and heat capacities, c;,,.The semi-empirical modelling procedures of Helgeson, Kirkham, and Flowers have been used to subdivide the calculated standard state volume and heat capacity data into solvation and nonsolvation contributions. The nonsolvation components of the standard state properties are used in group additivity analyses. These analyses yield structural contributions to standard state volumes and heat capacities for the CH(NH,)CO,H, CH,, OH, COOH, CH, CONH,, and CONH groups. The temperature dependences of these contributions are discussed. Some comments are reported concerning the practicality of using the thermodynamic properties of aqueous amino acid and peptide systems as the basis for modelling standard state thermodynamic properties of aqueous protein systems.Key words: heat capacities, densities, volumes, amino acids, peptides, group additivity. On rapporte quelques commentaires relatifs au caractere pratique de l'utilisation des propriCtCs thermodynamiques des systemes aqueux d'acides aminCs et de peptides pour la modClisation des propriCtCs thermodynamiques standard des systkmes aqueux de protkines.

Relative densities, [Formula: see text] and heat capacity ratios, [Formula: see text] have been measured for aqueous solutions of glycine, glycylglycine, and glycylglycylglycine in aqueous urea solutions containing 1–13 mol kg−1 urea. These data have been used to calculate apparent molar volumes, [Formula: see text] and apparent molar heat capacities, [Formula: see text] which in turn have been used to obtain standard state volumes, [Formula: see text] and standard state heat capacities, [Formula: see text].Volumes and heat capacities of transfer from water to urea have been calculated from our reported standard state data. Heat capacities of transfer of the investigated systems have been modeled using a procedure developed from the semiempirical calculation procedures proposed by Helgeson, Kirkham, and Flowers. Keywords: amino acids, peptides, calorimetry, transfer thermodynamics, HKF theory.