title: Neutron reflectivity studies of single lipid bilayers supported on planar substrates.
abstract: Neutron reflectivity was used to probe the structure of single phosphatidylcholine (PC) lipid bilayers adsorbed onto a planar silicon surface in an aqueous environment. Fluctuations in the neutron scattering length density profiles perpendicular to the silicon/water interface were determined for different lipids as a function of the hydrocarbon chain length. The lipids were studied in both the gel and liquid crystalline phases by monitoring changes in the specularly-reflected neutron intensity as a function of temperature. Contrast variation of the neutron scattering length density was applied to both the lipid and the solvent. Scattering length density profiles were determined using both model-independent and model-dependent fitting methods. During the reflectivity measurements, a novel experimental set-up was implemented to decrease the incoherent background scattering due to the solvent. Thus, the reflectivity was measured to Q approximately 0.3 A-1, covering up to seven orders of magnitude in reflected intensity, for PC bilayers in D2O and silicon-matched (38% D2O/62% H2O) water. The kinetics of lipid adsorption at the silicon/water interface were also explored by observing changes in the reflectivity at low Q values under silicon-matched water conditions.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: S
authors.initials: S
authors.lastname: Krueger
authors.forename: B W
authors.initials: BW
authors.lastname: Koenig
authors.forename: W J
authors.initials: WJ
authors.lastname: Orts
authors.forename: N F
authors.initials: NF
authors.lastname: Berk
authors.forename: C F
authors.initials: CF
authors.lastname: Majkrzak
authors.forename: K
authors.initials: K
authors.lastname: Gawrisch
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D017666:Deuterium Oxide; D008051:Lipid Bilayers / Q000737:chemistry*; D008968:Molecular Conformation; D015394:Molecular Structure; D009502:Neutrons; D010713:Phosphatidylcholines / Q000737:chemistry*; D012542:Scattering, Radiation; D012825:Silicon; D014867:Water
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; C010942:1,2-distearoyllecithin; D017666:Deuterium Oxide; D012825:Silicon