TEAR LIPOCALINS BIND A BROAD ARRAY OF LIPID LIGANDS

To identify the native ligands of tear lipocalins, tear proteins were separated by size exclusion chromatography and the lipid content in th e major protein fractions identified. Lipids extracted from native tea rs and purified tear lipocalins comigrated with fatty acids, fatty alc ohols, phospholipids, glycolipids, and cholesterol on thin layer chrom atograms. Abundant stearic and palmitic acids as well as cholesterol, and lesser amounts of lauric acid were specifically identified in extr acts of purified lipocalins by gas chromatography-mass spectroscopy. A preliminary study of the ligand-protein interaction was carried out u sing nitroxide spin-labeled lipids.