title: Structure of Cholesterol in Lipid Rafts.
abstract: Rafts, or functional domains, are transient nano-or mesoscopic structures in the plasma membrane and are thought to be essential for many cellular processes such as signal transduction, adhesion, trafficking, and lipid or protein sorting. Observations of these membrane heterogeneities have proven challenging, as they are thought to be both small and short lived. With a combination of coarse-grained molecular dynamics simulations and neutron diffraction using deuterium labeled cholesterol molecules, we observe raftlike structures and determine the ordering of the cholesterol molecules in binary cholesterol-containing lipid membranes. From coarse-grained computer simulations, heterogenous membranes structures were observed and characterized as small, ordered domains. Neutron diffraction was used to study the lateral structure of the cholesterol molecules. We find pairs of strongly bound cholesterol molecules in the liquid-disordered phase, in accordance with the umbrella model. Bragg peaks corresponding to ordering of the cholesterol molecules in the raftlike structures were observed and indexed by two different structures: a monoclinic structure of ordered cholesterol pairs of alternating direction in equilibrium with cholesterol plaques, i.e., triclinic cholesterol bilayers.
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Toppozini
authors.affiliation: KOMET 331, Institute of Physics, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Meinhardt
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada.
authors.forename: Clare L
authors.initials: CL
authors.lastname: Armstrong
authors.affiliation: Canadian Neutron Beam Centre, Chalk River, Ontario, K0J 1J0, Canada.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Yamani
authors.affiliation: Canadian Neutron Beam Centre, Chalk River, Ontario, K0J 1J0, Canada and Faculty of Pharmacy, Comenius University, 832 32 Bratislava, Slovakia.
authors.forename: Norbert
authors.initials: N
authors.lastname: Kučerka
authors.affiliation: KOMET 331, Institute of Physics, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Schmid
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canada and Canadian Neutron Beam Centre, Chalk River, Ontario, K0J 1J0, Canada.
authors.forename: Maikel C
authors.initials: MC
authors.lastname: Rheinstädter