Lipid glycosphingolipid

Rhodamine 6G long-chain hydrocarbons [169] squalene, a-amyrin [170] methyl esters of fatty acids [171] glycerides [91] sterols [172, 173] isoprenoids, quinones [HI] lipoproteins [174] glycosphingolipids [175] phenolic lipids [176] phosphonolipids [177] increasing the sensitivity after exposure to iodine vapor [178,179]... 

The Major Lipids in Mammalian Membranes Are Phospholipids, Glycosphingolipids, Cholesterol... 

The glycosphingolipids (GSLs) are sugar-containing lipids built on a backbone of ceramide they include galactosyl- and glucosylceramide (cerebrosides) and the gangliosides. Their structures are described in Chapter 14. They are mainly located in the plasma membranes of cells. 

Glycosphingolipids (GSLs) (neutral GSLs, gangliosides, and complex species, including the ABO blood group substances) constitute about 5-10% of the total lipid. 

Fabry s disease An x-linked recessive lipid storage disease with an accumulation of the glycosphingolipid. 

Cerebrosides are major constituents of the membrane of brain cells. They are the simplest glycosphingolipids, serving as model substances for more complex lipids of this kind. Furthermore, they are credited with important properties as receptors for hormones and toxins.29 Schemes 4 13 and 4 14 provide a method for preparing sphingosine and its analogs that can be used for the synthesis of cerebroside compounds. 

Due to the biological roles of glycolipids, many papers have been devoted to their syntheses over the last ten years. The coupling of a fully protected carbohydrate donor to a lipid acceptor requires efficient and highly stereoselective glycosylation methods because lipid derivatives often have low reactivity. A few examples of glycosphingolipids syntheses will be discussed below as well as multistep preparations of other amphiphilic carbohydrates designed as biochemical mimetics, surfactants or liquid crystals. 

Measurements of the quantities of glycolipids inserted into the membrane have also been reported by a technique based on the use of C-labeled lipid anchors. In this method, the carbohydrate (a-o-Man) was covalently coupled to the anchor at the surface of a pre-formed vesicle. Indeed, the liposome structure was shown to remain intact in the treatment. Nevertheless, the measurement of the incorporated mannose was performed after separation of bound and unbound material by centrifugation. The yields of coupling were shown to increase with the increase of the initial mannose/ C-anchor ratio, but non covalent insertions were displayed at high initial mannose concentrations. Therefore, the aforementioned method was not as accurate as could have been expected for the use of radioactive materials [142]. Radiolabeled phospholipids were also used for such determinations thus the amounts of glycosphingolipids incorporated into liposomes were quantified by the use of H-phospholipids whereas the amounts of glycolipids were determined by a sphingosine assay [143]. 

An article by Li and Li (Tnlane University, LA) on the biosynthesis and catabolism of glycosphingolipids serves to extend that by Kiss (Vol. 24), which dealt mainly with the chemistry of these compounds. Schwarz and Datema (Giessen) provide a detailed account of the lipid pathway of protein glyeosylation and of its inhibitors, and then discuss the biological significance of protein-bound carbohydrates, thereby... 

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