X-Ray Scattering from Gold Labeled Supported Membranes

Abstract

X-ray scattering is a promising tool with which to characterize systems of solid-supported 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 1,2-dipalmitoyl-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.