Application of osmometric methods to the study of lipids, lipoproteins, and apolipoproteins.

Membrane and vapor pressure osmometry are two colligative methods that can be useful in lipid research. The former method can be used to study proteins or other macromolecules whose molecular weight lies between 20,000 to 1,000,000. Vapor pressure osmometry is useful with smaller molecules having a molecular weight of 10,000 or less. These techniques can be used in aqueous or nonaqueous solutions. They are rapid, precise, nondestructive, and require relatively small amounts of material. These techniques provide information about the state of aggregation and also about interactions of lipids, lipoproteins, and apolipoproteins in solution. We will show how membrane osmometry can be used to study solutions of lipoproteins and apolipoproteins. The application of vapor pressure osmometry to the study of biologically important lipids such as cholesterol, cholesteryl esters, and bile salts is shown.