Glycosphingolipids membranes

Yu Z W, Calvert T L and Leckband D 1998 Molecular forces between membranes displaying neutral glycosphingolipids evidence for carbohydrate attraction Biochemistry 37 1540-50... 

GLYCOLIPIDS (GLYCOSPHINGOLIPIDS) ARE IMPORTANT IN NERVE TISSUES IN THE CELL MEMBRANE... 

Glycosphingolipids are constituents of the outer leaflet of plasma membranes and are important in cell adhesion and cell recognition. Some are antigens, eg, ABO blood group substances. Certain gangliosides function as receptors for bacterial toxins (eg, for cholera toxin, which subsequently activates adenylyl cyclase). 

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. 

Fig. 11.—Sequence of a 2S-Sugar Residue Glycosphingolipid Isolated from Rabbit Erythrocyte Membranes. (Cleavage points, and the masses of fragment ions of the permethylated derivative, are shown. No fragment-ions were observed above 4000, because of the poor sensitivity at high mass.)...

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. 

Another series of GSL mimics with oligo-ethylene glycol as spacer have also been obtained successfully using trichloroacetimidate method [482]. In addition, fluorescence-labeled sLex glycosphingolipids have also been chemically synthesized as targets for investigating microdomain formation in membranes [483]. 

Karlsson, K.-A. (1989). Animal glycosphingolipids as membrane attachment sites for bacteria. Annu. Rev. Biochem. 58, 309-350. 

Gangliosides are a class of glycosphingolipid characterized by the presence of one or more sialic acid residues. They are located in the cell membranes, particularly in the plasma membrane, of almost all cell types. They are anchored in the membranes through their ceramide moiety and have the polar sugar-containing group in the extracytoplasmic side. They are particularly abundant in the nervous system where their expression pattern is modulated during development. 

Guittard, J. Hronowski, X.L. Costello, C.E. Direct MALDI Mass Spectrometric Analysis of Glycosphingolipids on Thin Layer Chromatographic Plates and Transfer Membranes. Rapid Commun. Mass Spectrom. 1999,13, 1838-1849. 

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]. 

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