FLUORESCENCE ENERGY-TRANSFER IN LIPID VESICLES - A TIME-RESOLVED ANALYSIS USING STRETCHED EXPONENTIALS

Fluorescence energy transfer in lipid vesicles between N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-labelled phosphatidylethanolamine (acting as donor) and N-(lissamine-rhodamine B)-labelled phosphatidylethanolamine (acting as acceptor) was studied by steady state and time-resolved fluorescence quenching analysis. Both fluorescent phospholipids were incorporated as minor components in four different types of lipid vesicle: dipalmitoylphosphatidylglycerol vesicles in their L(beta) gel phase at 20 degrees C and in their L(alpha) liquid crystalline phase at 50 degrees C, and egg yolk phosphatidylethanolamine vesicles at 40 degrees C in their L(alpha) liquid crystalline phase at pH 9.5 and in their H-II inverted hexagonal phase at pH 5.0. The quenching of the donor fluorescence by energy transfer is diffusion controlled in all cases, except in the L(beta) gel phase. The dimensionality and type of constraints imposed on diffusion are different in each case, with the most efficient diffusion-controlled quenching in the hexagonal phase.