Lipid Control of Membrane Protein Organization

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DESCRIPTION (provided by applicant): A long-term goal of this laboratory has been to determine the role of lipid/protein interaction in the function of pulmonary surfactant. A more recent interest has been to determine the roles of the various lipid species in the structure of the barrier to permeability in skin. Two specific aims, each with a physical and biological/biomedical component related to these goals, will be pursued: Aim 1: Physical: To extend infrared reflection-absorption spectroscopy (IRRAS), for determination of elements of the 3-dimensional structure of lipid monolayers in situ at the A/W interface. Biological: To test the hypothesis that the hydrophobic surfactant proteins SP-B and C facilitate the formation/stabilization of multilayers that act as reservoirs for surface-active material during lung compression-expansion cycles. To complement IRRAS, Brewster angle microscopy, pressure-area isotherms, and pulsating bubble surfactometry will be used to characterize these films. Equivalent experiments with synthetic peptides will help define structural characteristics needed for peptides to be useful therapeutic agents for diseases such as respiratory distress syndrome. We will also evaluate the interactions of lung surfactant SP-A analogues with lipids and other ligands to determine its role in tubular myelin formation and in host defense. Aim 2: Physical: To apply 3 novel vibrational microscopic imaging technologies (IR microscopic imaging, confocal Raman microscopy, and attenuated total reflectance imaging) to acquire spatially resolved molecular structure information at distance scales from 1.5 mm to 4 mm. These will be used to study lipid domain formation in model systems for the skin barrier. The experiment aims to understand the role of the various ceramide species in barrier function. Biological: To use these methods to study the 3-D spatial distribution of the molecular constituents of skin as well as the permeation pathways of penetration enhancers and drug delivery vehicles. Finally, the sensitivity of vibrational spectra to molecular structure will be used to map the effects of penetration enhancers on lipid conformation and protein secondary structure.