MECHANICAL-PROPERTIES OF MODEL MEMBRANES STUDIED FROM SHAPE TRANSFORMATIONS OF GIANT VESICLES

Membrane deformations occur frequently in cell functioning. From the p hysical point of view, the understanding of such shape changes require s the introduction of mechanical parameters like bending elasticity. I n this article it is shown how this physical property can be obtained from the analysis of small or large shape transformations from giant v esicles. Then it is demonstrated that the bending modulus is strongly dependent on the membrane composition and environmental conditions. Th is is the case for one-component bilayers (dilauroylphosphatidylcholin e (DLPC), dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatid ylcholine and stearoyloleoylphosphatidylcholine (SOPC)) and for two-co mponent lipid mixtures (DMPC/cholesterol, DLPC/dilauroylphosphatidic a cid). Further it is shown that the bending elasticity of natural lipid extracts (egg phosphatidylcholine, digalactosyl diglyceride and red b lood cell lipid extracts) is generally smaller than that of comparable synthetic model membranes. The role of transmembrane proteins is exam ined by measuring the bending elasticity of SOPC/gramicidin mixtures. Finally, larger scale shape transformations of giant vesicles under an alternative electric field are discussed ((C) Societe francaise de bi ochimie et biologie moleculaire / Elsevier, Paris).