Preparation and properties of an apoprotein derivative of human serum β-lipoprotein

The aim of this study was to develop a convenient method for the preparation and study of a soluble delipidated form of human serum β-lipoprotein. This was achieved by succinylation and delipidation with ether-ethanol (3:1). The succinylated apoprotein was soluble in either 0.13 M Tris-HCl buffer, pH 8.2 (for β-lipoprotein prepared by ultracentrifugation) or in the same Tris buffer to which 5 mM sodium decyl sulfate was added (for heparin-Mn precipitated β-lipoprotein). The immunological activity of β-lipoprotein or its apoprotein were markedly altered by succinylation. Whereas the succinylated β-lipoprotein appeared as one peak in the analytical ultracentrifuge, the succinylated apoprotein appeared as two. Under the electron microscope β-lipoprotein and succinylated β-lipoprotein were indistinguishable, appearing as uniform preparations of spherical particles 215 to 220 A in diamater.