Search

Two one-dimensional systems for separation of glycolipids from total lipid extracts of tissues by thin-layer chromatography are described. System I used, as adsorbent, an alkaline mixture of silica gel without CaSO(4) binder (75%) and magnesium silicate (25%), and the lipids were "developed" with three successive solvent mixtures. The separated compounds (from the fastest to the slowest moving) were: ceramide, ceramide monohexosides, sulfatides, ceramide dihexosides, psychosine, ceramide trihexosides, and ceramide N-acetylhexosamine trihexosides. In system II a two-step development was used on an adsorbent consisting of silica gel without CaSO(4) binder (80%) and magnesium silicate (20%). The separated compounds were: ceramides, ceramide monohexosides, and ceramide dihexosides. Psychosine and sulfatides as well as ceramide trihexosides and ceramide N-acetylhexosamine trihexosides were not separated. In both systems all neutral lipids moved to the very top of the chromatogram and phospholipids stayed at the origin. Application of systems I and II for separation of glycolipids was demonstrated on total lipid extracts from animal tissues.

1. The lipid compositions of the low-density lipoproteins, the high-density lipoproteins and the ultracentrifugal residue of human serum are presented, with emphasis on certain lipoprotein classes and lipid components not previously described. 2. Except for the lipoproteins with the lowest and highest densities, there is a trend for stepwise successive increase or, respectively, decrease in the relative amounts of the main constituents of lipoproteins. 3. High-density lipoprotein-2 and high-density lipoprotein-3 have different amounts of certain lipids; high-density lipoprotein-2 has relatively more free cholesterol and sphingomyelin; high-density lipoprotein-3 has more free fatty acids, diglycerides and ceramide monohexosides. 4. All the lipoproteins contain hydrocarbons of the alkane series. The greatest amount, which averages 4.4% of total lipid extracted, is in the ultracentrifugal residue; n-alkanes comprise 18-50% of the hydrocarbons. 5. All the lipoproteins contain ceramide monohexosides. The highest relative contents of these glycolipids are in high-density lipoprotein-3 and in the ultracentrifugal residue. 6. The ultracentrifugal residue contains 55% of the total quantity of free fatty acids present in serum. The remaining free fatty acids are distributed among the other lipoprotein classes. 7. The choline-containing phospholipids (phosphatidylcholine, lysophosphatidylcholine and sphingomyelin) comprise about 90% of the phospholipids in all the lipoprotein classes except the low-density lipoprotein-2, which contains about 80% of these phospholipids. 8. The presence of a large amount of lysophosphatidylcholine in the ultracentrifugal residue and the successive decrease of sphingomyelin from the low-density lipoprotein-1 to the ultracentrifugal residue was confirmed. 9. The low-density lipoprotein-2 and the ultracentrifugal residue are characterized by relatively high contents of the lower glycerides.

Three high-denisity lipoprotein classes and one protein were separated from rat-liver plasma in membranes that had been treated with mild sonic oscillation. The lipoproteinis were separated and identified by techniques in which ultracentrifugation was used. Enzyme markers and electron-microscopic examination revealed membrane preparations essentially free of contaminating cellular partictulates.