MOLECULAR ORDER AND MOBILITY WITHIN LIPOSOMAL MEMBRANE MADE FROM HIGHLY FLUORINATED PHOSPHOLIPIDS

The temperature-dependent lipid structure, order and dynamics of membr anes formed by fluorinated DFnCmPC phosphatidylcholines, as compared t o their classical DMPC, DPPC and DSPC analogs, have been investigated using fluorescence anisotropy of an extrinsic fluorescent probe, i.e. trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). At low t emperatures and in the gel phase of the liposomal membranes, membrane fluidity was almost unaffected by the fluorocarbon or hydrocarbon natu re of the bilayer. In contrast, in the liquid-crystalline state, fluid ity decreased substantially near the membrane's surface when fluorinat ed chains were present. The most important rigidifying effect was obse rved for a chain ended by a C8F17 tail as in DF8C5PC. It was also foun d that an acyl chain ended by a fluorinated tail as short as C4F9 e.g. inDF(4)C(11)PC, induced, in the fluid state a rigidifying effect simi lar to that of cholesterol.