Ultracentrifugal study of liposome solubilization by sodium dodecylsulfate

Viscoelastic properties of mixed micelles formed upon interaction of liposomes (89% phosphatidylcholine and 11% phosphatidic acid) with sodium dodecylsullate (SDS) were investigated using analytical ultracentrifugation, viscometry and light scattering to elucidate the mechanisms of liposome solubilization. The peak in viscosity observed at certain SDS concentrations was correlated with sedimentation coefficient and dynamic light scattering results. The effective size of mixed micelles showed a maximum at peak viscosity. The undissolved liposomes were the dominant factor in determining the sedimentation coefficient but had little effect on the viscosity itself. In the case of completely solubilized systems, results suggest the shape of mixed micelles transform from sphere to rod and such transformation is the governing process determining the viscosity and sedimentation coefficient of the system.