FLUORESCENCE LIFETIME MEASUREMENTS TO MONITOR MEMBRANE LIPID MIXING

This chapter describes fluorescence lifetime measurements to monitor membrane lipid mixing. The only lipid mixing assay utilizing an intensive probe property is the DPHpPC fluorescence. Several fluorescent probes have been developed to monitor the intermembrane mixing of lipids during membrane fusion. The chapter explains how fluorescence lifetime measurements are used to monitor lipid exchange in model membrane systems induced to fuse by polyethylene glycol (PEG). It also examines the features of the probe, which make it useful not only for this fusion assay, but also as a probe for fusion-independent lipid exchange, phase separation, and formation of membrane domains. The aspects of the technique that limit its effectiveness as a tool for studying membrane fusion or the other membrane processes are also mentioned. to monitor the mixing of membrane phospholipid compartments by using the DPHpPC fluorescent lifetime lipid mixing assay, calibration curves must be generated by measuring the lifetime of the probe at different lipid/probe ratios. Because the lifetime of a fluorophore is dependent on the environment in which it resides, separate calibration curves must be generated for each lipid system studied. © 1993