Volumetric, compressibility and viscometric studies on sodium cholate/sodium deoxycholate-amino acid interactions in aqueous medium

This paper reports density, speed of sound, and viscosity data for the bile salts: sodium cholate (1-30 mmol kg(-1)) and sodium deoxycholate (1-17 mmol kg(-1)) in 0.1 mol kg(-1) aqueous solution of amino acids viz. glycine, leucine, methionine, and histidine at different temperatures (293.15-318.15 K) under atmospheric pressure. From the experimental density and speed of sound data, the apparent molar volume (phi(v)), isentropic compressibility (kappa(s)), and apparent molar isentropic compression (phi(kappa)) have been calculated, and the results have been interpreted in terms of different hydrophobic and electrostatic interactions pertaining in the bile salt-amino acid-water ternary system. Based on experimental viscosity data, the relative viscosity (eta(r)) and viscous relaxation time (tau) have been calculated and their dependence on concentration of bile salts and temperature has confirmed the existence of significant amount of bile salt-amino acid interactions. (C) 2015 Elsevier B.V. All rights reserved.