Partial molar volumes of some amino acids and a peptide in water, DMSO, NaCl, and DMSO/NaCl aqueous solutions

The partial molar volumes of glycine, DL-alanine, DL-serine, DL-threonine, L-histidine and glycylgIycine were obtained in water and aqueous solutions of 0.15 mol . dm(-3) dimethyl sulfoxide, 2.0 mol . dm(-3) sodium chloride a nd 0.15 mol . dm(-3) dimethyl sulfoxide/2.0 mol . dm(-3) sodium chloride at T = (278.15, 288.15, 298.15, and 308.15) K from the measurements of densit y. The data show that a low molarity of DMSO (0.15 mol . dm(-3)) exerts st slight influence on the partial molar volume of amino acids and peptides. H owever a 2.0 mol . dm(-3) sodium chloride aqueous solution changes the part ial molar volumes of amino acids and peptides considerably. The transfer vo lumes of amino acids and peptides from water to aqueous solutions of sodium chloride are positive and may be regarded as a result of a dominant intera ction between sodium chloride ions and the charged centres of amino acids a nd peptides. Their partial molar volume variations with temperature are dis cussed. (C) 2000 Academic Press.