Properties and Structure of Lipoproteins

1. Extraction of serum lipoproteins of density less than 1.063 g ml with ether produces 2 distinct ultracentrifugal components. One is associated with higher density lipoproteins and the other with lower density lipoproteins in the density group less than 1.063. In a case of essential hyperlipemia and with hyperlipemic rabbit serum only the moiety associated with lowest density lipoproteins was present. It would appear that both components are necessary in transformation of lower density lipoproteins to higher ones. Absence of the higher density moiety might result in an accumulation of lipid in lower density lipoproteins as occurred in the case of essential hyperlipemia and lipemic rabbit serum. 2. Also, it was demonstrated that both alpha and beta lipoproteins bind cholesterol in vitro. This finding suggests the possibility that serum cholesterol levels may partially depend upon this mechanism of combination.