Phase transition affects energy transfer efficiency in phospholipid vesicles

The fluorescence quenching of 6-propioiiyl-2-dimethylaminonaphtatene (PRODAN) and 6-dodecanoyl-2-dimethylaininonaphtalene (LAU-RDAN) by octadecyl rhodamine B (ORB) in a model system of small unilamellar vesicles (SUV) of dipalmitoylphosphatidyl-choline (DPPC) was investigated. Non-linear Stern-Volmer behaviour was observed in both systems in the gel phase (25 degrees C) and in the fluid phase (50 degrees C), resulting from association processes and from static quenching. The relative quenching efficiencies of both dyes depend on the phase state of the bilayer and indicate a deeper incorporation of PRODAN and LAURDAN into the membrane in its fluid phase than in its gel phase. (c) 2004 Elsevier B.V. All rights reserved.