Structure and Fluidity of Asymmetric Planar Lipid Bilayers

Kent State University, Kent OH

Investigators

Abstract

[unreadable] DESCRIPTION (provided by applicant): Biomembranes are laterally heterogeneous, vertically asymmetric fluid multi-component structures. Membrane asymmetry as well as the formation of domains is a prerequisite for many biological processes and the development of appropriate model systems for the investigation of these biomembrane features is highly desirable. It is proposed to establish asymmetric planar lipid bilayers floating near solid surfaces as biomem- brane models (solid-supported floating bilayer membranes, ssFBM) by characterizing their in-plane and out- of-plane structure on various length scales and their in-plane dynamics (lateral fluidity). While most of the optical microscopy and IR/Raman spectroscopy work for characterization of the in-plane chemical com- position and homogeneity, as well as fluorescence correlation spectroscopy (PCS) to characterize the in- plane dynamics of the system will be performed at Kent State University, structural work to identify the out- of-plane structural characteristics with submolecular resolution will be performed at the NISI Center for Neutron Research (NCNR) using neutron reflection techniques. Specifically, interface sensitive neutron scattering at deeply buried surfaces will provide information about the submolecular structure normal to the membrane. Surface enhanced Raman scattering and ATR-IR will be used to image the lateral distribution of lipid components within the terminal bilayer and most importantly, to obtain molecular structure information. PCS will provide layer specific information about the lateral heterogeneity as well as the fluidity of the respec- tive fluorophore environment. Initially the proposed study will be concerned with the characterization of homogeneous (one-component) and vertically heterogeneous (two-component) systems. These experiments will establish a point of reference and are expected to answer fundamental questions: How are the structure and fluidity of a phosphocholine layer affected by a second layer which is less fluid. In the next step, these studies will be extended to systems with in-plane heterogeneity (domains). Lipid raft domains have been associated with a large variety of signaling events and are believed to affect a broad range of human disease states. Transmembrane coupling in rafts and the effect of lipid asymmetry on raft mediated signaling events are presently only poorly understood. The research outlined in this prosposal aims to establish a model membrane system for the biophysical characterization of these important aspects of membrane function. [unreadable] [unreadable] [unreadable]