title: Characterisation of membrane mimetics on a dual polarisation interferometer.
abstract: Dual polarisation interferometry (DPI) has been used to characterise the formation of hybrid bilayer membranes (HBM) on a silicon-oxynitride surface. This technique allows the simultaneous determination of multiple physical properties of an HBM, as the HBM is being formed in a single experiment: mass, thickness in the z-direction (normal to the surface), tilt angle of the first layer and refractive index. Decanoic acid was covalently attached to an amine modified silicon-oxynitride sensor chip surface via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride condensation reaction. The decanoic acid layer was 0.92+/-0.12 nm thick, indicating a tilt angle of 57 degrees from surface normal, and possessed a mass of 1.05+/-0.10 ng mm(-2) and a refractive index (RI) of 1.450+/-0.020. Phospholipid vesicles made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were injected over the fatty acid surface to form an HBM. The DPPC HBM was 4.32+/-0.68 nm thick, with a total mass of 3.18+/-0.60 ng mm(-2) and a RI of 1.404+/-0.007. The DMPC HBM was 2.12+/-0.34 nm thick, with a total mass of 2.25+/-0.51 ng mm(-2), and a RI of 1.435+/-0.007. DPI thus provides an insight into HBM formation and differences between the structural organisation of HBMs of different composition.
authors.affiliation: School of Biological Sciences, Biosciences Building, Crown Street, University of Liverpool, Liverpool L69 7ZB, UK. cjterry@liv.ac.uk
authors.forename: Carla J
authors.initials: CJ
authors.lastname: Terry
authors.forename: Jonathan F
authors.initials: JF
authors.lastname: Popplewell
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Swann
authors.forename: Neville J
authors.initials: NJ
authors.lastname: Freeman
authors.forename: David G
authors.initials: DG
authors.lastname: Fernig
mesh_terms: D040761:Biomimetic Materials / Q000032:analysis / Q000737:chemistry*; D008051:Lipid Bilayers / Q000032:analysis / Q000737:chemistry*; D008081:Liposomes / Q000032:analysis / Q000737:chemistry*; D008422:Materials Testing / Q000379:methods*; D008560:Membrane Fluidity; D008567:Membranes, Artificial; D008857:Microscopy, Interference / Q000295:instrumentation / Q000379:methods*; D008859:Microscopy, Polarization / Q000295:instrumentation / Q000379:methods*
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D008567:Membranes, Artificial