Doris H. Bauer

Isolation and properties of protein fractions from navy beans (Phaseolus vulgaris) which inhibit growth of rats

Abstract A protein fraction which inhibits growth of weanling rats was obtained from Phaseolus vulgaris seeds of the Sanilac variety by extraction with sodium chloride solution and removal of extraneous materials by precipitation at pH 4.0 and absorption on 1:1 bentonite-Celite. The protein was precipitated by 0.75 saturation with ammonium sulfate. The growth inhibiting protein fraction contained at least four different proteins separable by electrophoresis, ultracentrifugation, immunodiffusion, and gel chromatography. Only one of the soluble proteins inhibited rat growth, and it comprised about 35% of the total growth inhibiting fraction and had hemagglutinating activity, stimulated leucocytes, contained very little trypsin inhibitor activity, and had an isoelectric point of pH 5.2 and a mol. wt of approx. 110 000. A protein which was insoluble at pH 4 and collected as a precipitate also inhibited growth of rats but because of the small amount isolated and its insolubility, it was not further studied.

Structure of egg yolk very low density lipoprotein. Polydispersity of the very low density lipoprotein and the role of lipovitellenin in the structure

Abstract Egg yolk very low density lipoprotein contained on the average 75% of lipid which could be extracted by ether and 25% of a residual lipoprotein, the classical lipovitellenin. The ether-extracted lipid was composed of 75% triglycerides, 7% sterols, 2% mono- and diglycerides, and 16% phospholipids. Lipovitellenin contained 48% lipid composed of 87% phospholipids, 11% triglycerides, and 2% sterols. The protein vitellenin was composed for the most part of units of 74,000 and 270,000 daltons molecular weight. Egg yolk very low density lipoprotein is polydisperse. Preparative ultracentrifugation separated it into six fractions of different average molecular size, and gel chromatography separated it into five. The fractions of larger molecular size contained more lipid and triglyceride than did the fractions of smaller molecular size. The proteins of the fractions appeared to be similar. Egg yolk very low density lipoproteins appear to be a series of molecules composed of cores of lipid of varying sizes with each core surrounded by a layer of lipovitellenin, which is composed principally of glycoprotein and phospholipid.