Volumetric and conductometric studies on the interactions of dipeptides with sodium acetate and sodium butyrate in aqueous solutions at T=298.15 K

Densities and conductivity data for the sodium carboxylate (sodium acetate and sodium butyrate)-dipeptides t(glycyl-L-glutamine and L-alanyl-L-glutamine) + water) systems were determined at T = 298.15 K. The apparent molar volumes of the peptides and the molar conductivity (Lambda) of sodium acetate and sodium butyrate have been calculated. These data have been utilized to deduce the standard partial molar volumes (V degrees(2,Phi)), standard partial molar volumes of transfer for clipepticle from water to aqueous sodium carboxylate solutions (Delta V-t degrees), volumetric interaction coefficient, the limiting molar conductivity (Lambda degrees), and Walden product (Lambda degrees eta). Both V degrees(2,Phi) and Delta V-t degrees for the dipeptides increase with increasing concentration of sodium carboxylate. The interpretation is that this result arises from the dominant interactions of the sodium carboxylate with the charged group and polar groups of pepticles. The decrease in A. of sodium carboxylate with increasing dipepticle concentration and nonconstant Walden product are attributed to the interactions of sodium carboxylate with pepticle and friction resistance of the solvent medium. (C) 2009 Elsevier Ltd. All rights reserved.