CHARACTERIZATION OF LIPOSOMES AND OTHER LIPID ASSEMBLIES BY MULTIPROBE FLUORESCENCE POLARIZATION

This minireview describes the use of fluorescence polarization to characterize the dynamics and organization of biological membranes, lipoproteins, liposomes and other lipid-based assemblies. The advantages, disadvantages and limitations of this method are discussed. There is special emphasis on the multiprobe approach, which can monitor various parts of the lipid membrane or assembly. The fluorescence polarization, anisotropy and the total fluorescence intensity are defined and their graphic presentation described. A user guide for the actual measurements is given. It describes how to apply fluorescence polarization, especially how to select the proper extrinsic probe and to optimize the measurement regarding theoretical and practical issues, the determination of a fluorescent probe location in the assembly, how to introduce the probe to the lipid assembly, what is the ideal ratio of the probe to the lipid, dealing with the spectrofluorimeter problems and how to overcome disturbances introduced by light scattering. It is shown here, that even though there are disadvantages in using fluorescence polarization, this approach provides a highly sensitive and simple means for assessing the subtle and more pronounced changes in the structure of lipid assemblies.