Studies in bile salt solutions: 1. Surface tension evidence for a stepwise aggregation model

Abstract

Measurement has been made of the surface tension, at 310.5 K, of solutions of sodium cholate, deoxycholate, chenodeoxycholate, dehydrocholate, and lithocholate at pH 7.00 in 0.01 mole dm −3 phosphate buffer; and of solutions of sodium glycocholate at pH values of 5.47, 4.90, and 4.07, of sodium glycodeoxycholate and glycochenodeoxycholate at pH values of 4.77 and 4.37, respectively, and of sodium taurocholate, taurodeoxycholate, and taurochenodeoxycholate at pH 4.09, all in 0.03 mole dm −3 acetate buffer. Values of the critical micelle concentration, CMC, have been determined. The surface tension plots for the taurine and glycine conjugates show discontinuities which have been discussed in terms of the phase separation and stepwise association models of aggregation.