EFFECT OF UNSATURATION ON LIPID DYNAMICS WITHIN SYNTHETIC LIPID-MEMBRANES

Unsaturated oleoyl (cis-2-F, cis-2-NF) and elaidoyl (trans-2-F, trans-2-NF) ammonium ion lipids were synthesized. Liposomes were created by sonication of 1:10 functional/nonfunctional lipid blends. These small (300 angstrom liquid crystal phase (T(c) < 25-degrees-C) liposomes were surface differentiated by exovesicular glutathione in an exovesicular/endovesicular pH gradient of 8/3.9. At 25-degrees-C, the liposomes were quite permeable to H+/OH- (t1/2 < 20 s) and reequilibrated rapidly by lipid flip-flop (t1/2(cis-2) < 1 min, t1/2(trans-2) approximately 4 min). In contrast, liposomes created from analogous, saturated stearoyl lipids (1:10 3-F/3-NF), where T(c) = 59-degrees-C, were less permeable to H+/OH- (t1/2 approximately 21 min) and less prone to transbilayer lipid migration after surface differentiation (t1/2 > 30 min at 40-degrees-C).