title: Structural studies of the monolayers and bilayers formed by a novel cholesterol-phospholipid chimera.
abstract: Langmuir isotherm, neutron reflectivity, and small angle neutron scattering studies have been conducted to characterize the monolayers and vesicular bilayers formed by a novel chimeric phospholipid, ChemPPC, that incorporates a cholesteryl moeity and a C-16 aliphatic chain, each covalently linked via a glycerol backbone to phosphatidylcholine. The structures of the ChemPPC monolayers and bilayers are compared against those formed from pure dipalmitoylphoshatidylcholine (DPPC) and those formed from a 60:40 mol % mixture of DPPC and cholesterol. In accord with previous findings showing that very similar macroscopic properties were exhibited by ChemPPC and 60:40 mol % DPPC/cholesterol vesicles, it is found here that the chimeric lipid and lipid/sterol mixture have very similar monolayer structures (each having a monolayer thickness of ∼26 Å), and they also form vesicles with similar lamellar structure, each having a bilayer thickness of ∼50 Å and exhibiting a repeat spacing of ∼65 Å. The interfacial area of ChemPPC, however, is around 10 Å(2) greater than that of the combined DPPC/cholesterol unit in the mixed lipid monolayer (viz., 57 ± 1 vs 46 ± 1 Å(2), at 35 mN·m(-1)), and this difference in area is attributed to the succinyl linkage which joins the ChemPPC steroid and glyceryl moieties. The larger area of the ChemPPC is reflected in a slightly thicker monolayer solvent distribution width (9.5 vs 9 Å for the DPPC/cholesterol system) and by a marginal increase in the level of lipid headgroup hydration (16 vs 13 H(2)O per lipid, at 35 mN·m(-1)).
authors.affiliation: Pharmaceutical Science Division, King's College London, Franklin Wilkins Building, 150 Stamford Street, London SE1 9NH, United Kingdom.
authors.forename: F
authors.initials: F
authors.lastname: Foglia
authors.forename: D J
authors.initials: DJ
authors.lastname: Barlow
authors.forename: F C
authors.initials: FC
authors.lastname: Szoka
authors.forename: Z
authors.initials: Z
authors.lastname: Huang
authors.forename: S E
authors.initials: SE
authors.lastname: Rogers
authors.forename: M J
authors.initials: MJ
authors.lastname: Lawrence
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D002784:Cholesterol / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008567:Membranes, Artificial; D008958:Models, Molecular; D015394:Molecular Structure; D013499:Surface Properties
chemical_list: D008051:Lipid Bilayers; D008567:Membranes, Artificial; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol