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Post‐source decay mass spectrometry: optimized calibration procedure and structural characterization of permethylated oligosaccharides
Author(s) -
Viseux Nelly,
Costello Catherine E.,
Domon Bruno
Publication year - 1999
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199904)34:4<364::aid-jms787>3.0.co;2-p
Subject(s) - chemistry , glycosidic bond , oligosaccharide , mass spectrometry , fragmentation (computing) , chromatography , yield (engineering) , organic chemistry , materials science , computer science , metallurgy , enzyme , operating system
Permethylated oligosaccharides were analyzed bymatrix‐assisted laser desorption/ionization massspectrometry (MALDI/MS) using a reflectrontime‐of‐flight instrument in the post‐sourcedecay (PSD) mode. Under these ionization conditions, suchderivatives yield intense signals corresponding to sodium orpotassium cationized molecular species. Fragments observed in the PSDspectra result exclusively from cleavage of glycosidic bonds,preferentially at N ‐acetylhexosamine residues. Asystematic study was carried out on a series of permethylatedoligosaccharides to allow rationalization of the fragmentationprocesses. Fragments originating from both the reducing and thenon‐reducing ends of the oligosaccharide yield information onsequence and branching. Moreover, glycosyl residues linked inposition 3 of HexNAc units give rise to a highly specific eliminationprocess, which allows unambiguous assignment of (1–3)interglycosidic linkages. Special attention was paid to thestructural analysis of oligosaccharides carrying the commonlyencountered fucosyl and sialyl end‐caps. In the case ofsialylated residues, a targeted methodology involving desialylationand specific CD 3 ‐labeling of the nascent freehydroxyl groups was developed to mark the initial location of sialicacid residues along the oligosaccharide backbone. As accurate massdetermination of fragment ions is essential for their assignment, asimplified protocol for the calibration in the PSD mode is described.This procedure allows the determination of the correction functionparameters required to process the data for an instrument thatemploys post‐acceleration detection. MALDI/PSD‐MSof permethylated oligosaccharides, by providing structuralinformation at the low picomole level, appears to be a valuablecomplement, or an alternative, to the techniques currently in use forcarbohydrate structural analysis. Copyright © 1999 John Wiley& Sons, Ltd.