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

The temperature-dependent lipid structure, order and dynamics of membranes formed by fluorinated DFnCmPC phosphatidylcholines, as compared to their classical DMPC, DPPC and DSPC analogs, have been investigated using fluorescence anisotropy of an extrinsic fluorescent probe, i.e. 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). At low temperatures and in the gel phase of the liposomal membranes, membrane fluidity was almost unaffected by the fluorocarbon or hydrocarbon nature of the bilayer. In contrast, in the liquid-crystalline state, fluidity decreased substantially near the membrane's surface when fluorinated chains were present. The most important rigidifying effect was observed for a chain ended by a C8F17 tail as in DF8C5PC. It was also found 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 similar to that of cholesterol.