THE INTERPRETATION OF THE TIME-RESOLVED FLUORESCENCE ANISOTROPY OF DIPHENYILHEXATRIENE-PHOSPHATIDYLCHOLINE USING THE COMPOUND MOTION MODEL

Time-resolved fluorescence anisotropy experiments on lipid membranes c an provide estimates of the molecular order and motion on microscopic scales. For the analysis of anisotropy data the socalled compound moti on model. was recently introduced to overcome problems with convention al models. We show that this novel model gives good fits for the time- resolved anisotropy of the fluorescent probe diphenylhexatriene-phosph atidylcholine (DPHPC) and can be succesfully used to interpret experim ents with DPHPC embedded in small unilamellar vesicles of the lipids D MPC, POPC, DOPC, DLPC, DERPC, DOPE, POPE, EGGPG and SQDG. The lifetime and order parameters are found to be intermediate between those found for the related DPH and TMA-DPH fluorescent probes, while the rotatio nal diffusion of DPHPC is much slower. These findings can be rationali sed in terms of the position of the DPH-fluorophore of DPHPC in the bi layer. (C) 1994 Academic Press, Inc.