Chromatofocusing of apolipoproteins from human serum high density lipoprotein

Human HDL was delipidated and the apolipoproteins were fractionated by chromatofocusing. Chromatofocusing, which separates proteins due to their differing isoelectric points, resulted in 8 peaks with corresponding pI values of 7.40, 6.92, 6.64, 5.48, 5.30, 5.18, 4.92 and 4.63. By one single chromatofocusing run four apolipoproteins were obtained in pure form. Two additional polypeptides could be purified during the desalting step using phenyl-Sepharose.     

A rheological study on plasma lipoproteins (author's transl)]

Lipoproteins of the types LpB and LP-X are studied in a microviscometer to measure intrinsic viscosity. Up to a shear rate of 1700s-1 no shear dependence of viscosity is observed. Intrinsic viscosities are 3.5 and 4.0 for LpB, and 8.5 ml/g for LP-X. Density measurements are used to calculate apparent specific volumes. The results are compatible with a spherical model. An upper limit of 0.45 is estimated for the hydration.     

The separation of human serum high density lipoproteins by hydroxy apatite column chromatography. Evidence for the presence of discrete subfractions.

Human serum high density lipoprotein subfractions 2 and 3, isolated by preparative ultracentrifugation after blocking the enzyme phosphatidylcholine: cholesterol acyl transferase, have been subfractionated further by hydroxyapatite column chromatography. From subfraction 2 we reproducibly obtained 5 and from subfraction 3, 6 fractions differing in chemical composition and apolipoprotein content. The fractions eluting at low salt concentrations were composed primarily of apolipoprotein-A polypeptides while those eluting at high salt concentrations consisted primarily of apolipoprotein-C. From all the 11 subfractions only one contained the "arginine-rich" polypeptide. The apolipoprotein-C-containing fractions were richer in triacylglycerol, phospholipids and free cholesterol as compared to the apolipoprotein-A-containing ones. Although small differences of their partial specific volumes existed, the obtained values indicate that all subfractions belonged to the parent density class. The implications of these results to the current view of lipoprotein metabolism are discussed.