Molecular sizes of egg yolk very low density lipoproteins fractionated by ultracentrifugation

Abstract

Egg yolk very low density lipoproteins isolated from normal eggs were separated into six fractions by preparative ultracentrifugation. The sizes of the molecules in three of the fractions were estimated by gel chromatography and by electron microscopy of the lipoproteins using a negative staining technique. The three fractions had average diameters of 39 nm., 32 n., and 25 nm. and average molecular weights of 17 X 10(6), 10 X 10(6), and 5 X 10(6). There was considerable overlap of size of molecules in the three fractions. Size differences were not observed in the ultracentrifuge separated fractions of very low density lipoproteins isolated from eggs laid by hens receiving crude cottonseed oil in their diets. However, the fatty acids from these fractions differed in stearic and oleic acid contents while those from the normal egg lipoproteins did not. The floating very low density lipoproteins contained more oleic acid and less stearic acid then the sedimenting ones did.