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Biophys J. 2008 Sep;95(5):2356-67. doi: 10.1529/biophysj.108.132662. Epub 2008 May 23.

Lipid bilayer structure determined by the simultaneous analysis of neutron and X-ray scattering data.

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1
Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario K0J 1J0, Canada. norbert.kucerka@nrc.gc.ca

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.

PMID:
18502796
PMCID:
PMC2517047
DOI:
10.1529/biophysj.108.132662
[Indexed for MEDLINE]
Free PMC Article
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