Determination of the composition of mixed micelles of bile salts by kinetic dialysis

A kinetic dialysis method for determining the critical micelle concentration and the composition of mixed micelles has been adapted to study a binary system of bile acids. Using kinetic dialysis, the critical micelle concentrations of taurocholate, deoxycholate and taurodeoxycholate were determined. Monomer analysis was performed by colorimetric and radioactive tracer techniques on aliquots of the dialysates. Similarly, the composition of mixed micelles made from various molar fractions of deoxycholate and taurocholate containing tritium and¹⁴C tracers were determined by this method. The results suggest that, for these bile acids, mixed micelle composition is largely predicted by the molar composition of the binary system. Kinetic dialysis has proven to be a rapid procedure and to yield results that agree with critical micelle concentration values previously reported.