Glycolipids permethylated, mass spectrometry

Figure 3. Selected ion monitoring from mass spectrometry of a permethylated-reduced mixture of non-acid glycolipids from non-epithelial residue of the white rat...

Figure 11. Selected ion monitoring from mass spectrometry of glycolipids of epithelial cells of the two rat strains. A total of 200 fig each of the permethylated-reduced mixture was evaporated by a temperature rise of 5°C/min, and mass spectra were recorded each 38 sec. Electron energy was 34 eV, acceleration voltage 4 kV, trap current 500 fiA, and ion source temperature 290°C.

The carbohydrate sequence can be studied by the partial hydrolysis of glycolipids and by the use of specific glycosidase, the most specific and useful method for sequential degradation of carbohydrates. The sugar sequence in glycolipids may be elucidated by mass spectrometry, using acetylated or permethylated glycolipids (28,29). 

Methylation is the most widely used method to determine the position of the glycosyl linkages.Permethylation of glycolipids can be done according to the methods of Hakomori (32) and Ciucanu and Kerek (33). The permethylated derivatives are hydrolyzed and the products converted into partially methylated alditol acetates and identified by gas chromatography-mass spectrometry ( CG-MS) (34). 

The structural diversity and labile nature of the bonds that link the various building blocks have posed a serious challenge to the characterization of glycol-ipids. Complete structural characterization of GSLs requires structure elucidation of the constituents of the ceramide and sugar portions. In a classical mass spectrometry method, glycolipids are cleaved into individual structural units and are analyzed by EI-MS or GC/MS after conversion to a suitable derivative, such as by the acetylation, permethylation, or permethylation-reduction reaction. 

Mass spectrometry has also been useful in revealing sialic acid as a bound component of glycolipids (gangliosides). Permethylated ganglio-sides have proved more useful for this purpose than the trimethylsilyl derivatives (Karlsson, 1973 Ledeen et aLy 1974 Karlsson, 1974 Karls-son et aLy 1974 Price et aLy 1975). Abundant primary ions are produced... 

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