[Lipoproteins associated with lipoprotein B in human serum low density lipoproteins]

Small amounts of lipoprotein C and lipoprotein D could be observed in low density lipoproteins (1.030-1.055 g/ml), using electroimmunomigration and polyacrylamide gel electrophoresis. Lipoprotein structures containing several apolipoproteins such as lipoprotein (B+C) or (B+D) were not detected in these low density lipoproteins. Lipoproteins C and D could not be separated from lipoprotein B by using gel filtration and affinity chromatography on heparin-Sepharose. Apolipoproteins C-III and D measured by electroimmunoassay are 3.2 +/- 1.2% and 1.15 +/- 0.6%, respectively, of the proteins found in the density range 1.030-1.055 g/ml, so there is, therefore, about 1 mol of apolipoprotein C-III and 0.1 mol of apolipoprotein D per mol of apolipoprotein B.