Structural Characterization of pH Responsive Polymer Cushions for Solid Supported Membranes

Abstract

Solid supported lipid bilayers are highly useful model systems for cell membranes. However, the close proximity of the membrane and the solid support may adversely impact protein structure and mobility. One approach to screen the membrane from the underlying support and to better mimic the cellular cytoskeleton and the extracellular matrix is to fabricate a water rich polymer cushion between the solid support and the lipid bilayer (1). In this talk, I will describe a robust and versatile, pH sensitive poly(acrylic acid) (PAA) polymer cushion that has been developed to elevate and decouple biomimetic lipid bilayers from solid supports (2). Importantly, structural details of PAA cushions obtained using synchrotron based high resolution x-ray reflectivity and neutron reflectivity clearly demonstrate the structure of the cushioned membrane system and its response to environmental pH changes. Complimentary fluorescence recovery after photobleaching (FRAP) measurements demonstrate high membrane mobility and integrity of the membrane. The system is easily tailored for a variety of applications and shows enormous potential for bio-sensing, probing membrane environmental interactions and investigations of integral membrane proteins embedded into lipid bilayers on top of PAA cushions. 1. Sackmann, E. 1996. Supported membranes: scientific and practical applications. Science 271:43. 2. El-khouri, R. J., D. A. Bricarello, E. B. Watkins, C. Y. Kim, C. E. Miller, T. E. Patten, A. N. Parikh, and T. L. Kuhl. 2011. pH Responsive Polymer Cushions for Probing Membrane Environment Interactions. Nano Letters 11:2169-2172.