title: Cholesterol reduces membrane electroporation and electric deformation of small bilayer vesicles.
abstract: Electric fields, similar in the order of magnitude of the natural membrane fields of cellular lipid/protein membranes, and chemical relaxation spectrometry can be used as tools to quantify the rigidifying effect of cholesterol in membranes. Small unilamellar vesicles of radius a=50+/-3 nm, prepared form phosphatidylcholine, phosphatidylserine and phosphatidyl-glycerol in the molar ratio 1:1:1 and containing the optical lipid probe molecule 2-(3-diphenyl-hexatrienyl) propanoyl)-1-palmitoyl-sn-glycerol-3-phosphocholine (beta-DPH pPC), serve as examples for curved lipid membranes. The data of electrooptical turbidity and absorbance relaxations at the wavelength lambda=365 nm are analysed in terms of membrane bending rigidity kappa and membrane stretching modulus K. Both kappa and K increase with increasing mole fraction x of cholesterol up to x=0.5. The cholesterol induced denser packing of the lipids reduces the extent of both membrane electroporation (ME) and electroelongation of the vesicles. Further on, cholesterol in the lipid phase and sucrose in the aqueous suspension reduce the extent of membrane undulation and electro-stretching.
authors.affiliation: Physical and Biophysical Chemistry, Faculty of Chemistry, University of Bielefeld, P.O. Box 100 131, D-33501 Bielefeld, Germany.
authors.forename: Sergej
authors.initials: S
authors.lastname: Kakorin
authors.forename: Ute
authors.initials: U
authors.lastname: Brinkmann
authors.forename: Eberhard
authors.initials: E
authors.lastname: Neumann
mesh_terms: D000818:Animals; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002784:Cholesterol / Q000737:chemistry* / Q000494:pharmacology; D004553:Electric Conductivity; D018274:Electroporation; D008051:Lipid Bilayers / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry; D013057:Spectrum Analysis / Q000379:methods; D055672:Static Electricity
chemical_list: D008051:Lipid Bilayers; D008563:Membrane Lipids; D002784:Cholesterol