title: Joint small-angle X-ray and neutron scattering data analysis of asymmetric lipid vesicles.
abstract: Low- and high-resolution models describing the internal transbilayer structure of asymmetric lipid vesicles have been developed. These models can be used for the joint analysis of small-angle neutron and X-ray scattering data. The models describe the underlying scattering length density/electron density profiles either in terms of slabs or through the so-called scattering density profile, previously applied to symmetric lipid vesicles. Both models yield structural details of asymmetric membranes, such as the individual area per lipid, and the hydrocarbon thickness of the inner and outer bilayer leaflets. The scattering density profile model, however, comes at a cost of increased computational effort but results in greater structural resolution, showing a slightly lower packing of lipids in the outer bilayer leaflet of ∼120 nm diameter palmitoyl-oleoyl phosphatidyl-choline (POPC) vesicles, compared to the inner leaflet. Analysis of asymmetric dipalmitoyl phosphatidylcholine/POPC vesicles did not reveal evidence of transbilayer coupling between the inner and outer leaflets at 323 K,i.e.above the melting transition temperature of the two lipids.
authors.affiliation: Instiute of Molecular Biosciences, Biophysics Division, University of Graz, Austria; BioTechMed-Graz, Graz, 8010, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Eicher
authors.affiliation: The Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, TN, USA; Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Heberle
authors.affiliation: Instiute of Molecular Biosciences, Biophysics Division, University of Graz, Austria; BioTechMed-Graz, Graz, 8010, Austria.
authors.forename: Drew
authors.initials: D
authors.lastname: Marquardt
authors.affiliation: Instiute of Molecular Biosciences, University of Graz, Austria; Omics-Center Graz, BioTechMed-Graz, Austria.
authors.forename: Gerald N
authors.initials: GN
authors.lastname: Rechberger
authors.affiliation: Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: John
authors.initials: J
authors.lastname: Katsaras
authors.affiliation: Instiute of Molecular Biosciences, Biophysics Division, University of Graz, Austria; BioTechMed-Graz, Graz, 8010, Austria.
authors.forename: Georg
authors.identifier: https://orcid.org/0000-0003-1967-1536
authors.initials: G
authors.lastname: Pabst
keywords: asymmetric membranes; joint SAXS/SANS analysis; lipid bilayers; scattering density profile models; small-angle X-ray scattering (SAXS); small-angle neutron scattering (SANS); transbilayer coupling