Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Aq. micellar solns. of bile salts, sodium cholate (NaC) (1-30 mmol kg-1) and sodium deoxycholate (NaDC) (1-17 mmol kg-1) in the absence and presence of amino acids viz. glycine, leucine, methionine, and histidine (0.1 mol kg-1) have been examd. by surface tension and UV-visible measurements at different temps. (293.15-318.15 K). From the surface tension study, crit. micelle concn. (CMC) values of bile salts have been calcd. and reviewed in terms of effect of amino acids on the hydrophobic character of bile salt-amino acid complex. Further, the adsorption behavior of NaC and NaDC in aq. soln. of amino acids has been analyzed with the help of interfacial parameters like max. surface excess concn. (Gmax), min. area per surfactant mol. (Amin), surface pressure at CMC (CMC), efficiency in reducing surface tension (pC20), and adsorption at the air/water interface relation to micellization (CMC/C20). The thermodn. parameters, std. free energy of micellization (Gdegm), std. Gibb's free energy of adsorption (Gdegad), and std. free energy of transfer (Gdegtr) have also been calcd. UV-visible studies, by using pyrene as a probe, have also been carried out in order to substantiate the CMC values derived from surface tension studies.