Studies on the primary structure of short polysaccharides using SEC MALDI mass spectroscopy

The introduction of size-exclusion chromatography (SEC) analysis of polysac charides prior to MALDI mass spectroscopy accounts for the determination of the molecular mass of the repeating unit when neutral homopolymers are inv estigated. In the case of natural polysaccharides characterised by more com plicated structural features (presence of non-carbohydrate substituents, ch arged groups, etc.), this mass value usually is in agreement with more than one sugar composition. Therefore, it is not sufficient to give the correct monosaccharidic composition of the polysaccharide investigated. To solve t his problem, MALDI spectra were recorded on the permethylated sample and po st-source decay experiments were performed on precursor ions. In this way, the composition (in terms of Hex, HexNAc, etc.), size and sequence of the r epeating unit were determined. (C) 2000 Elsevier Science Ltd. All rights re served.