Calculation of Partition Coefficients of Chain Anchors in Liquid-Ordered and Liquid-Disordered Phases in Model Lipid Bilayers (original) (raw)

X-ray scattering is a promising tool with which to characterize systems of solidsupported membranes. There are many different scattering techniques used in the characterization, but all suffer from a necessarily low electron density contrast between the membrane and the water medium in which it must exist. Labeling membranes with a high-contrast scatterer such as gold is a promising avenue to solve this problem. In this work, silicon-supported membranes of 1,2dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were prepared by both standard Langmuir-Blodgett deposition and fusion of vesicles onto the substrate surface. Membranes are characterized using specular x-ray reflectometry, and modeled to fit physical systems. One percent by count 1,2-dipalmitoyl-sn-glycero-phosphoethanolamine (DPPE) with a gold tag attached was then added to both systems. Gold labeled membranes were then characterized and modeled. The effect of gold labeling is shown to characteristically change the membrane density profile in addition to enhancing density contrast between the membrane and the water medium. We created two-dimensional (2D) assemblies of tobacco mosaic viruses (TMVs) and characterized their structures using Atomic Force Microscopy (AFM) and X-ray scattering. The TMVs were adsorbed on an oppositely charged, fluid lipid monolayer supported by a solid substrate and submerged in a buffer solution. The lipid monolayer confined the viral particles within a plane, while providing them with lateral mobility so that overall the TMV assembly behaved like a 2D liquid. The inter-particle interaction is controlled by the chemical condition in the buffer. The degree of structural orders observed varied, depending on both the inter-particle interaction and the lateral mobility of the particles. Quantitative analysis of the X-ray scattering data provides information on the nature of the interaction between TMVs as well as possible membrane deformation due to the contact with TMVs. This study provides the proof-of-concept that X-ray scattering may be used to study the structure of membrane associated proteins in substrate-supported single bilayer under near-native conditions.