Influence of La3+ ions on the egg-yolk phosphatidylcholine and sodium taurocholate self-assemblies in aqueous suspension.

In this study, the influence of La3+ on the mixed egg-yolk phosphatidylcholine (EYPC)-sodium taurocholate (TC) aggregates was investigated by using turbidity, quasi-elastic light-scattering (QELS) technique, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). La3+ ions exert different effects on different EYPC-TC aggregates. The EYPC-TC mixed spheroidal micelles are stable in the presence of La3+ ions. The EYPC-TC vesicles are aggregated by the interaction of La3+ with the EYPC phosphate group. Particularly, La3+ causes structural transition of the EYPC-TC mixed disk micelles by changing the colloidal properties of TC. This process includes two steps, destruction of mixed disk micelles and formation of mixed spheroidal micelle. Several intermediate structures such as multi-lamellar vesicles and cylindrical micelles were observed during the transition. The experimental data and analysis in the current study suggest that metal ion is one of the important factors to control the structure of the EYPC-TC self-assemblies. And the possible influence of metal ions on the properties of bile biocolloid has been discussed.