title: Atomically detailed lipid bilayer models for the interpretation of small angle neutron and X-ray scattering data.
abstract: We present a new atom density profile (ADP) model and a statistical approach for extracting structural characteristics of lipid bilayers from X-ray and neutron scattering data. Models for five lipids with varying head and tail chemical composition in the fluid phase, 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC), 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylserine (POPS), and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG), are optimized using a simplex based method to simultaneously reproduce both neutron and X-ray scattering data. Structural properties are determined using statistical analysis of multiple optimal model structures. The method and models presented make minimal assumptions regarding the atomic configuration, while taking into account the underlying physical properties of the system. The more general model and statistical approach yield data with well defined uncertainties, indicating the precision in determining density profiles, atomic locations, and bilayer structural characteristics. Resulting bilayer structures include regions exhibiting large conformational variation. Due to the increased detail in the model, the results demonstrate the possibility of a distinct hydration layer within the interfacial (backbone) region.
authors.affiliation: Department of Physics, University of South Florida, Tampa, FL 33620, USA.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Fogarty
authors.affiliation: Centre for Modeling and Simulation, University of Pune, Pune 411007, India.
authors.forename: Mihir
authors.initials: M
authors.lastname: Arjunwadkar
authors.affiliation: Department of Physics, University of South Florida, Tampa, FL 33620, USA. Electronic address: pandit@usf.edu.
authors.forename: Sagar A
authors.initials: SA
authors.lastname: Pandit
authors.affiliation: Department of Physics, University of South Florida, Tampa, FL 33620, USA.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Pan
mesh_terms: D008051:Lipid Bilayers / Q000737:chemistry*; D008956:Models, Chemical; D033363:Neutron Diffraction; D010713:Phosphatidylcholines / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry; D011789:Quantum Theory; D012542:Scattering, Radiation; D014961:X-Ray Diffraction
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D010718:Phosphatidylserines; C021016:1,2-diphytanoylphosphatidylcholine; C050294:1-palmitoyl-2-oleoylglycero-3-phosphoserine; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol; C017251:1,2-oleoylphosphatidylcholine; C028694:1-palmitoyl-2-oleoylphosphatidylcholine
keywords: Model membrane; SANS; SAXS; Simplex based optimization