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Strategies for characterization of ganglioside inner esters II—gas chromatography/mass spectrometry
Author(s) -
Levery Steven B.,
Roberts Carl E.,
Salyan Mary Ellen K.,
Bouchon Bernadette,
Hakomori Senitiroh
Publication year - 1990
Publication title -
biomedical and environmental mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0887-6134
DOI - 10.1002/bms.1200190506
Subject(s) - chemistry , glycosidic bond , ganglioside , mass spectrometry , methylation , residue (chemistry) , acetylation , gas chromatography , derivatization , chromatography , stereochemistry , organic chemistry , biochemistry , dna , enzyme , gene
Two novel gas chromatography/mass spectrometry (GC/MS) strategies have been developed to assist in characterization of ganglioside inner esters. In the first, lactonized gangliosides which have been ammonolyzed and permethylated (see previous paper) are subjected to methanolysis and acetylation. This produces partially methylated NeuAc derivatives in which previous involvement of the carboxyl group in an ester linkage is indicated by conversion to an N 1 , N 1 ‐dimethylamide. These can be analyzed by GC/MS using conditions analogous to those used normally in NeuAc methylation analysis, providing glycosidic and ester linkage information in the same procedure. In the second procedure, internally esterified NeuAc hydroxyl groups are located by protection, under neutral conditions, of all free hydroxyl groups of the ganglioside lactone with methoxyethoxymethyl groups, followed by permethylation, methanolysis, and GC/MS analysis of the resulting partially methylated NeuAc methyl ester methyl glycosides as their per‐ O ‐trimethylsilylates or per‐ O ‐acetates. This procedure has been used to show unambiguously that in GD 3 lactones it is the 9‐hydroxyl group of the internal NeuAc residue which is esterified by the terminal NeuAc carboxyl. Both of these strategies should have general application in characterizing lactones occurring in gangliosides, NeuAc homo‐ and heteropolymers, and oligosaccharides or glycopeptides terminated by polysialosyl chains.