title: Cholesterol monohydrate nucleation in ultrathin films on water.
abstract: The growth of a cholesterol crystalline phase, three molecular layers thick at the air-water interface, was monitored by grazing incidence x-ray diffraction and x-ray reflectivity. Upon compression, a cholesterol film transforms from a monolayer of trigonal symmetry and low crystallinity to a trilayer, composed of a highly crystalline bilayer in a rectangular lattice and a disordered top cholesterol layer. This system undergoes a phase transition into a crystalline trilayer incorporating ordered water between the hydroxyl groups of the top and middle sterol layers in an arrangement akin to the triclinic 3-D crystal structure of cholesterol x H(2)O. By comparison, the cholesterol derivative stigmasterol transforms, upon compression, directly into a crystalline trilayer in the rectangular lattice. These results may contribute to an understanding of the onset of cholesterol crystallization in pathological lipid deposits.
authors.affiliation: Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: H
authors.initials: H
authors.lastname: Rapaport
authors.forename: I
authors.initials: I
authors.lastname: Kuzmenko
authors.forename: S
authors.initials: S
authors.lastname: Lafont
authors.forename: K
authors.initials: K
authors.lastname: Kjaer
authors.forename: P B
authors.initials: PB
authors.lastname: Howes
authors.forename: J
authors.initials: J
authors.lastname: Als-Nielsen
authors.forename: M
authors.initials: M
authors.lastname: Lahav
authors.forename: L
authors.initials: L
authors.lastname: Leiserowitz
mesh_terms: D000388:Air; D002784:Cholesterol / Q000737:chemistry*; D002788:Cholesterol Esters / Q000737:chemistry*; D003460:Crystallization; D008051:Lipid Bilayers / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D013265:Stigmasterol / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D002788:Cholesterol Esters; D008051:Lipid Bilayers; D008563:Membrane Lipids; D014867:Water; D002784:Cholesterol; D013265:Stigmasterol; C060123:cholesterol acetate