title: Asymmetric distribution of cholesterol in unilamellar vesicles of monounsaturated phospholipids.
abstract: We have studied the effect of cholesterol on curved bilayers using 600 A unilamellar vesicles made of monounsaturated lipids. From small-angle X-ray scattering experiments we were able to detect an asymmetric distribution of lipid densities across certain bilayers. We discovered that, with the exception of diC24:1PC bilayers, monounsaturated diacylphosphatidylcholine lipids (diCn:1PC, n = 14, 16, 18, 20, and 22) form symmetric bilayers. However, the addition of 44 mol % cholesterol resulted in some of these bilayers (i.e., n = 14, 16, and 18) to become asymmetric, where cholesterol was found to distribute unequally between the bilayer's two leaflets. This finding is potentially of relevance to biological membranes made up of different types of lipids and whose local curvature may be dictated by lipid composition.
authors.affiliation: Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario K0J 1J0, Canada. Norbert.Kucerka@nrc.gc.ca
authors.forename: Norbert
authors.initials: N
authors.lastname: Kucerka
authors.forename: Mu-Ping
authors.initials: MP
authors.lastname: Nieh
authors.forename: John
authors.initials: J
authors.lastname: Katsaras
mesh_terms: D002784:Cholesterol / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008956:Models, Chemical; D010743:Phospholipids / Q000737:chemistry*; D012542:Scattering, Radiation; D053835:Unilamellar Liposomes / Q000737:chemistry*; D014965:X-Rays
chemical_list: D008051:Lipid Bilayers; D010743:Phospholipids; D053835:Unilamellar Liposomes; D002784:Cholesterol