Alterations in serum proteins following delipidization by 2-octanol.

The demonstration of a role for serum lipoproteins in lipid transport in health and disease has stimulated interest in the biological activity of the lipid and protein moieties of these substances. For these investigations the development of improved methods for separating the lipids from whole serum or from the serum lipoproteins themselves is important but fully acceptable methods are not yet available. Nonpolar solvent extraction of lipids from serum may be quantitative, but usually involves gross denaturation of the proteins. Treatment of serum with polymers such as dextran sulfate or high-molecular-weight polyethylene glycols has been useful in isolating lipoproteins from serum, but these methods do not remove the lipids from the lipoproteins. Ultracentrifugation with density gradient techniques accomplishes essentially the same result as polymer isolation. Hardy and Gardner' in 1910 were able to remove substantial amounts of lipids from serum by ether extraction but only after first freezing the serum and then extracting it at low temperatures. Macheboeuf and Sandor' succeeded in removing considerable quantities of lipid from serum without gross protein denaturation by combining small, nonprecipitating amounts of alcohol with ether for extraction. Macheboeuf and Tayeau8 have separated appreciable quantities of lipids from serum by treatment with salts of certain long-chain fatty acids. Finally Avignan,' returning to the ether method, has succeeded in removing most of the lipids from low density (D < 1.063) serum lipoproteins by prolonged shaking with ether (16 hours at 4°C). Addition of alcohol to ether was required for separation of the lipids of the high density (D > 1.063) serum lipoprotein fraction. Recently a relatively simple and effective technique for the removal of cholesterol from serum together with a substantial fraction of the other serum lipids has been described.' This method involves treatment of the serum with