Title: Solid-Supported Bilayer Lipid Membranes from Lipid Mixtures: Structure and Composition
Abstract: Biological membranes are of overarching importance for all aspects of cell structure and function in living organisms. Planar tethered bilayer lipid membranes (tBLMs) are synthetic membrane models stabilized by the proximity of a solid substrate that enhances its long-time stability by orders of magnitude.[1,2] A nanometer-thin hydration layer between the bilayer and the substrate ensures that the biomimetic lipid membrane remains fluid with in-plane lipid dynamics similar to that in vesicles.[3] In this work we establish tBLMs composed of binary and ternary lipid mixtures as more complex, and hence more realistic, membrane models. Such membranes may be used for studies of protein-membrane interactions.[4] Biophysical properties of mixed tBLMs vary significantly with bilayer composition. We report a structural and compositional characterization by neutron reflectometry of tBLMs that comprise various lipid compositions including cholesterol. With specific deuteration of selected bilayer components, such studies enable the determination of volume fractions of individual lipid species in the asymmetric tBLM. A new composition-space model was developed to interpret neutron reflectivity data of such systems. This model enables for the first time to extract more detailed information about the bilayer leaflet proximal to the substrate and lets us explore in more detail the distribution of lipid components across the bilayer. Such a detailed structural and compositional assessment is the prerequisite for more detailed studies of the association of amyloid-beta oligomer particles with membranes in studies on the origin of Alzheimer's disease.[4] Supported by the NIH (1P01AG032131) and the AHAF (A2008-307). [1]D.J. McGillivray, et al.2007. Biointerphases 2:21-33. [2]F. Heinrich, et al. 2009. Langmuir 25:4219-4229. [3]S. Shenoy, et al. 2009. Soft Matter, submitted. [4]G. Valincius, et al., 2008. Biophys. J. 95:4845-4861.