Mass spectrometry, glycolipids

Neutral gangliolipids from Thermoplasma acidophilum were separated by PTLC, and their tentative structures were characterized by the combination of GC, H-NMR, and FAB-mass spectrometries [91]. The lipophilic portion of the neutral glycolipid was composed of caldarchaeol (dibiphytanyl-diglycerol tetraether), and the sugar moieties of the glycolipids were composed of glucose. 

Ramsay SL, Maire I, Bindloss C, Fuller M, Whitfield PD, Piraud M, Hopwood JJ, Meikle PJ (2004) Determination of oligosaccharides and glycolipids in amniotic fluid by electrospray ionisation tandem mass spectrometry in utero indicators of lysosomal storage diseases. Mol... 

Conventional electron impact or chemical ionization mass spectrometry requires that volatilization precede ionization and this is clearly a limiting factor in the analysis of many biochemically significant compounds. A newer ionization technique, field desorption (FD) (1, 2 ) removes this requirement and makes it possible to obtain mass spectrometric information on thermally unstable or non-volatile organic compounds such as glycoconjugates and salts. This development is particularly significant for those concerned with the analysis of glycolipids and we have therefore explored the suitability of field desorption mass spectrometry (FDMS) for this class of compounds. We have evaluated experimental procedures in order to enhance the efficiency of the ionization process and to maximize the information content of spectra obtained by this technique. 

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.

Plasma-desorption mass spectrometry is another technique that has been applied successfully to the detection of readily removable fatty acyl substituents in intact glycolipids and their acylated derivatives. The specific location of the fatty acyl substituents in the ring of the glycosyl residues, as in LOS antigens, is determined by methylation under nonbasic conditions (see Section II.lb), followed successively by O-deacylation, ethylation of the exposed hydroxyl groups, and GC-MS analysis of partially alkylated alditol acetates21 ethyl groups denote the sites of previous O-acylation. 

Li, J., Martin, A., Cox, A.D., Moxon, E.R., Richards, J.C., Thibault, P. Mapping bacterial glycolipid complexity using capillary electrophoresis and electrospray mass spectrometry. Methods Enzymol 405 (2005b) 369-397. 

Analytical methods for tocol analysis have continued to improve, as noted by Abidi (2000), and in the intervening ten years, as noted in this chapter. We predict that advances will continue to be made in the field of the chromatographic analysis of tocols. Also, we believe that lipidomic methods (quantitative analysis via direct injection tandem electrospray ionization mass spectrometry) will be developed for the rapid analysis of tocols, just as these methods have already been used for the profiling of phospholipids and glycolipids (Han, 2011 Welti, 2011). These methods usually involve the direct injection of lipid samples into a... 

Otsuka, K. Yamakawa, T. The apphcation of droplet counter-current chromatography (DCC) forthe separation of acidic glycolipids. J. Biochem. (Tokyo) 1981,90,247-254. Kim, Y. Wang, T.C. Ma, Y.C. Liquid chromatography/ mass spectrometry of phosphohpids using electrospray ionization. Anal. Chem. 1994, 66, 3977. 

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). 

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