Partial molal adiabatic compressibilities of transfer of some amino acids and peptides from water to aqueous sodium chloride and aqueous glucose solutions

Abstract

Partial molal adiabatic compressibilities at infinite dilution have been determined for glycine, dl-alanine, diglycine and triglycine in water, 1 M aqueous sodium chloride and 1 M aqueous glucose solutions by measuring sound velocities at 298.15 K. In the case of water, our results show a non-linear relationship between the partial molal adiabatic compressibility at inifinite dilution ( K ⊖ s,2 ) and the number n of glycyl units for n = 1–3, and the results have been compared with the literature values. The data have been used to derive partial molal adiabatic compressibilities of transfer at infinite dilution ( K ⊖ S,2,tr ) from water to 1 M aqueous sodium chloride and to 1 M aqueous glucose solutions. All transfer values are found to be positive which in the case of sodium chloride results from the dominant interactions between the ions of sodium chloride and the charged centres of amino acids or peptides. However, in the case of glucose these have been discussed in terms of the interactions between ions (charged centres), hydrophilic groups (OH and CONH) and hydrophobic groups.