Volumetric investigations on interactions of Acidic/Basic amino acids with sodium acetate, sodium propionate and sodium butyrate in aqueous solutions

The apparent molar volumes, V (phi) , of L-aspartic acid, L-glutamic acid, L-lysine monohydrate and L-arginine in water and in aqueous (0.1, 0.25, 0.5 and 1.0) mol center dot kg(-1) sodium acetate and sodium propionate, and (0.1, 0.25 and 0.5) mol center dot kg(-1) sodium butyrate solutions have been determined at 288.15, 298.15, 308.15 and 318.15 K from density measurements. The partial molar volumes at infinite dilution, V-2 degrees, obtained from V (phi) data, have been used to calculate hydration numbers and partial molar expansibilities of amino acids in water and in the presence of the studied cosolutes at different temperatures. These parameters have been discussed in terms of various interactions between the acidic/basic amino acids and organic salts in these solutions. The effect of the hydrophobic chain length of the carboxylate ions has also been discussed.