title: Lipid bilayer structure determined by the simultaneous analysis of neutron and X-ray scattering data.
abstract: Quantitative structures were obtained for the fully hydrated fluid phases of dioleoylphosphatidylcholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) bilayers by simultaneously analyzing x-ray and neutron scattering data. The neutron data for DOPC included two solvent contrasts, 50% and 100% D(2)O. For DPPC, additional contrast data were obtained with deuterated analogs DPPC_d62, DPPC_d13, and DPPC_d9. For the analysis, we developed a model that is based on volume probability distributions and their spatial conservation. The model's design was guided and tested by a DOPC molecular dynamics simulation. The model consistently captures the salient features found in both electron and neutron scattering density profiles. A key result of the analysis is the molecular surface area, A. For DPPC at 50 degrees C A = 63.0 A(2), whereas for DOPC at 30 degrees C A = 67.4 A(2), with estimated uncertainties of 1 A(2). Although A for DPPC agrees with a recently reported value obtained solely from the analysis of x-ray scattering data, A for DOPC is almost 10% smaller. This improved method for determining lipid areas helps to reconcile long-standing differences in the values of lipid areas obtained from stand-alone x-ray and neutron scattering experiments and poses new challenges for molecular dynamics simulations.
authors.affiliation: Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario K0J 1J0, Canada. norbert.kucerka@nrc.gc.ca
authors.forename: Norbert
authors.initials: N
authors.lastname: Kucerka
authors.forename: John F
authors.initials: JF
authors.lastname: Nagle
authors.forename: Jonathan N
authors.initials: JN
authors.lastname: Sachs
authors.forename: Scott E
authors.initials: SE
authors.lastname: Feller
authors.forename: Jeremy
authors.initials: J
authors.lastname: Pencer
authors.forename: Andrew
authors.initials: A
authors.lastname: Jackson
authors.forename: John
authors.initials: J
authors.lastname: Katsaras
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D003198:Computer Simulation; D008051:Lipid Bilayers / Q000737:chemistry*; D008958:Models, Molecular; D033363:Neutron Diffraction; D010713:Phosphatidylcholines / Q000737:chemistry*; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D015060:1,2-Dipalmitoylphosphatidylcholine; C017251:1,2-oleoylphosphatidylcholine