Temperature-induced micelle to vesicle transition: kinetic effects in the DMPC/NaC system

The formation of spherical and monodisperse small unilamellar vesicles is observed upon temperature jumps in a mixed system composed of a phospholipid (dimyristoylphosphatidylcholine) and a bile salt (sodium cholate) in an aqueous buffer. In order to enhance the X-ray contrast of the system a mixed water/sucrose buffer is used. The spontaneous formation of unilamellar structures from mixed micelles upon temperature increase and the reverse solubilisation of membranes upon cooling is studied by means of synchrotron radiation small-angle X-ray scattering. The variations of the vesicle size are presented when the temperature and the surfactant / lipid ratio are modified. The kinetic conditions leading to monodisperse vesicles as well as the reversibility of the micelle to vesicle transition are investigated.