These projects are directed towards a greater understanding of the quaternary organization of plasma lipoproteins and of the function of the oligomeric species involved in the transport and metabolism of lipids in plasma. The apolipoprotein composition of plasma lipoproteins is viewed as the governing factor in directing lipoprotein metabolism. Specificity is believed to be related directly to apolipoprotein secondary, tertiary and quaternary structure. Studies of the molecular properties of plasma lipoproteins have been extended to include lipoprotein lipase. Purification of lipoprotein lipase and hepatic lipase from human post-heparin plasma has been initiated. Studies of the molecular properties of radiolabeled apolipoproteins have been extended to include in vivo metabolic studies with apolipoprotein A-1. A knowledge of the specific interactions and quaternary organiztion of plasma lipoprotein complexes is fundamental to our ultimate understanding of lipid metabolism.