title: Hybrid and nonhybrid lipids exert common effects on membrane raft size and morphology.
abstract: Nanometer-scale domains in cholesterol-rich model membranes emulate lipid rafts in cell plasma membranes (PMs). The physicochemical mechanisms that maintain a finite, small domain size are, however, not well understood. A special role has been postulated for chain-asymmetric or hybrid lipids having a saturated sn-1 chain and an unsaturated sn-2 chain. Hybrid lipids generate nanodomains in some model membranes and are also abundant in the PM. It was proposed that they align in a preferred orientation at the boundary of ordered and disordered phases, lowering the interfacial energy and thus reducing domain size. We used small-angle neutron scattering and fluorescence techniques to detect nanoscopic and modulated liquid phase domains in a mixture composed entirely of nonhybrid lipids and cholesterol. Our results are indistinguishable from those obtained previously for mixtures containing hybrid lipids, conclusively showing that hybrid lipids are not required for the formation of nanoscopic liquid domains and strongly implying a common mechanism for the overall control of raft size and morphology. We discuss implications of these findings for theoretical descriptions of nanodomains.
authors.affiliation: Biology and Soft Matter and §Biosciences Divisions, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Heberle
authors.forename: Milka
authors.initials: M
authors.lastname: Doktorova
authors.forename: Shih Lin
authors.initials: SL
authors.lastname: Goh
authors.forename: Robert F
authors.initials: RF
authors.lastname: Standaert
authors.forename: John
authors.initials: J
authors.lastname: Katsaras
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Feigenson
mesh_terms: D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry* / Q000378:metabolism; D021962:Membrane Microdomains / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D033363:Neutron Diffraction; D053838:Scattering, Small Angle; D013050:Spectrometry, Fluorescence
chemical_list: D008563:Membrane Lipids; D002784:Cholesterol