Lipid bilayer structure determined by the simultaneous analysis of neutron and X-ray scattering data.
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.
Kucerka
Norbert
N
Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario K0J 1J0, Canada. norbert.kucerka@nrc.gc.ca
Nagle
John F
JF
Sachs
Jonathan N
JN
Feller
Scott E
SE
Pencer
Jeremy
J
Jackson
Andrew
A
Katsaras
John
J
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
D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D015060:1,2-Dipalmitoylphosphatidylcholine; C017251:1,2-oleoylphosphatidylcholine