MACROMOLECULAR PROPERTIES OF VITELLENIN FROM EGG YOLK AND ITS PARENT COMPLEX WITH LIPIDS

Abstract

The floating fraction of egg yolk (90% lipid, density 0.98) appears to be heterogeneous but no significant fractionation took place during centrifugation in several solvents of density 0.98 or higher. This fraction had a particle size several times that of the lipoprotein (50% lipid) remaining after ether extraction. Most of the so-called "free" lipid extracted by ether is apparently part of, or associated with, the lipoprotein.The lipid-free vitellenin was not soluble in mild aqueous solvents and most of the physical measurements were made in 88% formic acid solutions. Molecular weights ranged from 3.0 to 9.0 × 104. The higher value, considered most reliable, was only half the estimated size of the protein part of the lipid-containing materials. Evidently the protein portion of the lipoprotein has two or more polypeptide chains that may be combined directly or through lipid by forces weaker than the peptide linkage.