A simple assay to study protein-mediated lipid exchange by fluorescence polarization

We investigated the protein-mediated phospholipid transfer between small vesicles by fluorescence polarization measurements with diphenylhexatriene as optical probe. Thermotropic-phase-transition curves were taken after mixing two vesicle preparations of lipids exhibiting different gel-to-liquid phase transitions. From the heights of each phase-transition step we were able to follow the lipid transfer process without separating the two vesicle preparations.