Deformation of giant lipid vesicles by electric fields

We deform spherical giant vesicles made of lipid bilayers, egg yolk phosphatidylcholine (EYPC), 1,2-dilaureoyl-sn-3-phosphatidylcholine (DLPC), l-palmitoyl-2-oleoyl-sn-3-phosphatidylcholine (POPC), and digalactosyldiacylglycerol (DGDG), into prolate ellipsoids of revolution by means of alternating electric fields. The lateral tensions stretching the vesicle membrane are calculated from the Maxwell stress tensor and the eccentricity of the ellipsoid. The apparent increase of membrane area with tension, being due to a flattening of thermal undulations, permits us to determine the bending rigidities. We obtain 2.47×${10}^{\mathrm{-}20}$ J for EYPC, 3.37×${10}^{\mathrm{-}20}$ J for DLPC, 2.46×${10}^{\mathrm{-}20}$ J for POPC, and 1.01×${10}^{\mathrm{-}20}$ J for DGDG, with errors of up to 20%. These values are slightly smaller than those reported to date for the same materials.