title: Analysis of simulated NMR order parameters for lipid bilayer structure determination.
abstract: The conventional formula for relating CD2 average order parameters <Sn> to average methylenic travel <Dn> is flawed when compared to molecular dynamics simulations of dipalmitoylphosphatidylcholine. Inspired by the simulated probability distribution functions, a new formula is derived that satisfactorily relates these quantities. This formula is used to obtain the average chain length <LC>, and the result agrees with the direct simulation result for <LC>. The simulation also yields a hydrocarbon thickness 2<DC>. The result <LC> = <DC> is consistent with a model of chain packing with both early chain termination and partial interdigitation of chains from opposing monolayers. The actual simulated area per lipid <A> is easily obtained from the order parameters. However, when this method is applied to NMR order parameter data from dimyristoylphosphatidylcholine, the resulting <A> is 10% larger than the currently accepted value.
authors.affiliation: Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: H I
authors.initials: HI
authors.lastname: Petrache
authors.forename: K
authors.initials: K
authors.lastname: Tu
authors.forename: J F
authors.initials: JF
authors.lastname: Nagle
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D055592:Biophysical Phenomena; D001703:Biophysics; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D006838:Hydrocarbons / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000031:analogs & derivatives / Q000737:chemistry; D015394:Molecular Structure; D013816:Thermodynamics
chemical_list: D006838:Hydrocarbons; D008051:Lipid Bilayers; C030011:carbene; D015060:1,2-Dipalmitoylphosphatidylcholine; D008697:Methane; D004134:Dimyristoylphosphatidylcholine