title: Location of cholesterol in liposomes by using small-angle X-ray scattering (SAXS) data and the generalized indirect Fourier transformation (GIFT) method.
abstract: We investigated the location of cholesterol (Chol) in liposomes and its interaction with phospholipids using small-angle x-ray scattering (SAXS) data and applying the generalized indirect Fourier transformation (GIFT) method. The GIFT method has been applied to lamellar liquid crystal systems and it gives quantitative data on bilayer thickness, electron density profile, and membrane flexibility (Caillé parameter). When the GIFT method is applied to the SAXS data of dipalmitoylphosphatidylcholine (DPPC) alone (Chol [-]) or a DPPC/Chol = 7/3 mixed system (Chol [+], molar ratio), change in the bilayer thickness was insignificant in both systems. However, the electron density for the Chol (+) system was higher than that for the Chol (-) system at the location of hydrophilic groups of phospholipids, and whereas Caillé parameter value increased with temperature for the Chol (-) system, no significant change with temperature was observed in the Caillé parameter for the Chol (+) system. These results indicated that Chol is located in the vicinity of the hydrophilic group of the phospholipids and constricts the packing of the acyl chain of phospholipids in the bilayer.
authors.affiliation: Faculty of Science and Technology, Tokyo University of Science.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Aburai
authors.forename: Taku
authors.initials: T
authors.lastname: Ogura
authors.forename: Ryo
authors.initials: R
authors.lastname: Hyodo
authors.forename: Hideki
authors.initials: H
authors.lastname: Sakai
authors.forename: Masahiko
authors.initials: M
authors.lastname: Abe
authors.forename: Otto
authors.initials: O
authors.lastname: Glatter
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry*; D004583:Electrons; D005583:Fourier Analysis; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers; D008081:Liposomes / Q000737:chemistry*; D050866:Liquid Crystals; D010743:Phospholipids / Q000737:chemistry*; D053838:Scattering, Small Angle; D013696:Temperature; D014965:X-Rays
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D010743:Phospholipids; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol