Determination of the linkages in some methylated, sialic acid-containing, meningococcal polysaccharides by mass spectrometry.

The application of gas-liquid chromatography-mass spectrometric (g.l.c.-m.s.) analysis to a number of sialic acid-containing polysaccharides of meningococcal origin has been studied. Methylation of these polysacchardies by the Hakomori conditions resulted in both O- and N-methylation. Methanolysis of the methylated polysaccharides from serogroup C [(2 leads to 9)-linked], colominic acid [(2 leads to 8)-linked], and serogroups Y and W-135 [both (1 leads to 4)-linked], yielded the respective 4,7,8-, 4,7,9-, and 7,8,9-tri-O-methyl derivatives of methyl N-acetyl-N-methyl-beta-D-neuraminate methyl glycoside. As model compounds, methyl N-acetyl-4,7,8,9-tetra-O-methyl-alpha-D-neuraminate methyl glycoside and its N-methyl derivative were also synthesized. All of the methylated derivatives could be identified on the basis of their typical fragmentation-patterns, indicating that this method is applicable to the determination of the position of linkages to sialic acid residues in biopolymers.