The primary objective of the proposed research is to improve understanding of the structural organization of human plasma lipoproteins and of the molecular dynamics of the constituent lipid molecules. This information will be sought through 13C NMR spectroscopy at both conventional and high magnetic fields. We propose to bring to a conclusion our current studies on normal, unmodified human plasma lipoproteins and to extend our efforts to include chemically and enzymatically modified lipoproteins as well as those which are characteristic of pathological states: LP-X formed in obstructive liver jaundice; IDL formed in type III hyperlipoproteinemia; the abnormal lipoproteins formed in certain animals fed high-cholesterol diets. Primary indicators of structure and molecular dynamics will be linewidths and intensities, spin-lattice relaxation times, and nuclear Overhauser enhancements. The NMR studies are to be supplemented by work on lipolysis of lipoproteins and structural studies on certain lipid-protein complexes involving lipoprotein proteins.