Glycosphingolipids long-chain bases

FIGURE 9.4 TLC-blotting/SIMS of various glycosphingolipids. (A) TLC profile of the separated glycosphingolipids, (B) MS profiles obtained by TLC-blotting/SIMS (a) spectrum of sulfatide peaks at m/z 862, 876, 890, 906, and 918 are molecular ions with different fatty acid species indicated in the figure (asterisks are peaks of triethanolamine as matrix) (b) spectrum of Gb Cer peaks at m/z 1309 and 1337 are molecular ions with different fatty acid species as indicated (c) spectrum of G peaks at m/z 1151, 1235, and 1263 are molecular ions with different fatty acid species as shown. Abbreviations LCB — long chain base, FA — fatty acid, hFA — hydroxyfatty acid. Hex — hexose, HexNAc — /V-acetylhexosamine. (From Taki, T. et al.. Anal. Biochem., 225, 24—27, 1995. With permission.) Continued. 

Sphingatrienes also occur naturally but in minor amounts. Sphingomyelin isolated from squid nerve and from starfish contains a branched, triunsaturated sphingoid base, 2-amino-9-methyl-4 , 8 , 10 -octadecatriene-l,3-diol (10), and glycosphingolipids from starfish contain the same long-chain base without the methyl branch (9). 

The extraordinary multiplicity displayed by the glycosphingolipids results from the great variability of the three constituents that are common to all of them (1) sphingosine (long-chain base), (2) fatty acid, (3) carbohydrate. Certain more complex glycosphingolipids additionally contain sulfuric acid and, in the case of plant material, also phosphoric acid. 

The glycosphingolipids of Saccharomyces cerevisiae, Candida utilis, and Aspergillus niger (Wagner and Zofcsik, 1966a,b) contain tl8 0 and t20 0 long-chain bases and those of soya and maize tl8 0 and tl8 15 bases (Wagner et al., 1969). 

In more recent times, mass spectrometry was employed for determinations of the chemical structure of glycosphingolipids. Mass spectrometry of the fully trimethylsilylated intact lipids yields information about the position of substituents on the monosaccharide units, the nature of the long-chain base, and the relative amounts of constituent fatty acids (Sweeley and Dawson, 1969 K. Samuelsson and Samuelsson, 1969 Karlsson et al., 1969b). 

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