TRANSMEMBRANE PH-DRIVEN NA-BASED MEMBRANES( PERMEABILITY OF FLUORINATED PHOSPHOLIPID)

The permeability to the H+/Na+ exchange of fluorinated phospholipid-ba sed membranes has been evaluated by measuring the dissipation rate of a liposomal transmembrane pH gradient in the presence of Na+. The fluo rinated liposomes are made from fluorocarbon/hydrocarbon or fluorocarb on/fluorocarbon double-chain ether-connected glycerophosphocholines or amido-connected phosphocholines deriving from diaminopropanol or seri ne. The fluorocarbon/hydrocarbon mixed-chain phospholipids, as compare d to the fluorocarbon/fluorocarbon ones, form membranes that are subst antially more able to maintain a transmembrane pH gradient in the pres ence of Na+ and display a lower Na+ permeability. However, these membr anes are more permeable to the H+/Na+ exchange than conventional DSPC (1,2-distearoylphosphatidylcholine) ones. Our results indicate a detri mental impact of the membrane fluorination degree on H+/Na+ permeabili ty: the lower the fluorination degree of the membrane, the lower its H +/Na+ permeability. Concerning structure/permeability relationships, i t appears that the replacement of the ester connecting bond in their f luorinated phosphatidylcholine analogues for an ether or amide one low ers the transmembrane H+/Na+ exchange. (C) 1998 Elsevier Science B.V.