Aggregative behavior of bile salts in aqueous solution.

Formation of aggregates composed by sodium cholate (NaC), sodium deoxycholate (NaDC) and sodium glycocholate (NaGC), three constituents of bile fluid, either in pure or mixed combination in aqueous solution has been studied by means of intradiffusion, mutual diffusion, small angle neutron scattering and surface tensiometry techniques. The collected data have shown the formation of pure and mixed micelles with characteristics depending on the molecules involved and the relative amount, despite of their similar structure. Diffusion and scattering data has allowed highlighting the presence of ellipsoidal micelles with a relatively small aggregation number (~5÷10) at moderate concentrations c ≤10 mmol dm−3 and a scarce presence of counterions into the Stern layer. When the concentration of the solutes is increased, a micellar growth is observed. Such growth, according to scattering data, occurs along one dimension, leading to very elongated structures. Concerning the mixed systems, in particular NaC–NaDC–water system, experimental data have shown that the presence of deoxycholate promotes the micellization process and when the concentration of both the solutes is increased keeping fixed their ratio, mixed aggregates enrich in cholate molecules.