Cholesteryl ester-rich microemulsions: stable protein-free analogs of low density lipoproteins.

A method has been devised for the preparation of stable lipid microemulsions containing cholesterol, cholesteryl ester, phosphatidylcholine, and trioleoylglycerol in the relative molar ratios found in low density lipoproteins. Gel permeation chromatography showed these microemulsions to be essentially homogeneous with respect to chemical composition. Omission of triolein or substitution of a diunsaturated phosphatidylcholine for either a disaturated or monosaturated-monounsaturated phosphatidylcholine destroyed the observed homogeneity of the microemulsions. The particle diameter of the negatively-strained relative elution volumes of the cholesteryl ester-rich microemulsion, VLDL2, VLDL3, and LDL indicated a mean diameter of about 35 nm. The cholesteryl ester-rich microemulsion can be used as a cholesteryl ester donor for plasma protein-mediated transfer of cholesteryl ester to plasma lipoproteins and for studying apoprotein-lipid interactions.