Ethanol-ether, lipoprotein extraction

Attempts have been made in the author s laboratory to obtain a lipid-free water-soluble product from the d < 1.019 and d 1.019-1.063 low-density human serum lipoproteins by using the ethanol-ether procedure successfully applied to the high-density class (Scanu et al., 1958a). The precipitate obtained proved insoluble in the various buffered media alone or in the presence of 1-4 M urea. Banaszak and McDonald (1962) attempted separation of the protein moiety of d 1.019-1.063 serum lipoproteins by a pentane extraction of a lyophilized preparation. The product obtained, insoluble in common buffer solutions, was solubilized in carbonate buffer of pH 10.2 in the presence of 4 M urea, leading to prompt formation of a gel, which persisted after removal of urea by dialysis. 

Detailed studies of the apolipoproteins require the removal of the lipid from the lipoproteins. This can be achieved by extraction of the lipoproteins either direct from plasma or in the precipitated form with ethanol-diethyl ether mixtures (3 1, v/v). The more powerful lipid solvent, chloroform-methanol (2 1, v/v) results in a poorly soluble apolipoprotein. With ethanol-ether, however the advantage of having a soluble apoprotein is partly offset by the loss of 20% of VLDL protein. Lyophilization before... 

The presence of small amounts of carbohydrates in human serum lipoproteins has been reported by Schultze (1958) and Epstein and Block (1959). Scanu et al. (1958a) found that serum HDL contains 0.5% hexose and 0.35% hexosamine, which remains boimd to the protein after extraction of the lipid moiety by ethanol-diethyl ether. The carbohydrate moiety of serum lipoproteins of d < 1.0 has been reported to... 

Promotion of lipid extraction by ethanol was first observed by Bloor (1914) and later by Macheboeuf and Sandor (1932). Ethanol-diethyl ether mixtures have been successfully applied to the extraction of the entire lipid portion of ultracentrifugally separated lipoproteins. When the denaturing action of ethanol is prevented by low temperature, a soluble protein moiety essentially free of lipids can be obtained. The... 

---