Abstract
Permethylated derivatives of N-acetylneuraminic acid-containing GM3, N-glycolylneuraminic acid-containing GM3, GD1a, and GD1b, were analyzed by direct inlet ammonia chemical ionization (CI) mass spectrometry. These compounds were found to yield simple fragmentations, prominent fragment ions in the high mass region, and characteristic fragment ions corresponding to the cleavage of glycosidic linkages. This method also provides detailed information on the carbohydrate sequence and lipophilic composition in gangliosides.
Highlights
Intact permethylated and permethylated-reduced (LiAlH4) derivatives of GM1 ganglioside were analyzed by direct inlet ammonia chemical ionization (CI) mass spectrometry
We have recently reported that CI mass spectrometry can provide information about the molecular weights, the ceramide structures, and the sugar sequences of the oligosaccharides of a variety of neutral glycosphingolipids [25,26,27]
GM1 ganglioside in adult mammalian brain characteristically contains about equal amountsof C18 and C20 sphingosine, and less than 5% of other bases
Summary
GMl ganglioside from adult bovine brain was purified by DEAE-Sephadex A-25 column and Iatmbeads column chromatography according to the procedure of Momoi, Ando, and Nagai [28]. After the solution was allowed to stand for 30 min at O"C, 150pl of methyl iodide (freshly distilled) was added. T h e reaction mixture was incubated for 30 min at 0°C and dlowed to stand for 2 hr at room temperature. Reduction of permethylated GMI ganglioside was performed with LiAIH4 in diethyl ether for 3 h r at room temperature according to the method of Karlsson [21]. The purification of the methylated GMI ganglioside was achieved by thin-layer. AShimadzu-LKB gas chromatography-mass spectrometer 9000A equipped with a CI source was used. Th e temperature of the direct probe inlet was programmed from 100°C to 400°C at the rate of about 50°C per minute. T h e total ion collector and mass spectra were monitored continuously during theheating.
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