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Matrix‐assisted laser desorption/ionisation mass spectrometry for the direct analysis of enzymatically digested kappa ‐ iota ‐ and hybrid iota / nu ‐carrageenans
Author(s) -
Antonopoulos Aristotelis,
Hardouin Julie,
Favetta Patrick,
Helbert William,
Delmas Agnès F.,
Lafosse Michel
Publication year - 2005
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2051
Subject(s) - chemistry , mass spectrometry , fragmentation (computing) , desorption , ion , matrix assisted laser desorption/ionization , analytical chemistry (journal) , matrix (chemical analysis) , deprotonation , chromatography , crystallography , organic chemistry , adsorption , computer science , operating system
Enzymatically digested oligosaccharides of kappa ‐, iota ‐ and hybrid iota / nu ‐carrageenans were analysed using matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry in the negative‐ion mode. nor ‐Harmane was used as matrix. Depending on the stock concentration and the laser intensity applied, the oligosaccharides exhibited losses of sulphate units (neutralised by the Na + ion, and thus non‐stable), leaving the primary backbone structure in most cases with only the deprotonated sulphate groups (carrying the negative charge, stable). This meant that kappa ‐ and iota ‐oligosaccharides could not be easily distinguished from one another since they share the same primary backbone structure. However, for the hybrid iota / nu ‐oligosaccharides the primary backbone structure could be identified since the nu ‐carrageenan repeating unit differs from that of the kappa / iota ‐carrageenan unit. For all types of oligosaccharides, the results indicated cleavage of an anhydrogalactose unit from the non‐reducing end. Specifically, for the hybrid oligosaccharides of iota / nu ‐carrageenans, this type of fragmentation means that the nu ‐carrageenan unit is not positioned on the non‐reducing end of the hybrid oligosaccharides. Dehydration reactions, and exchange reactions of Na + with K + and Ca 2+ , were also observed. Copyright © 2005 John Wiley & Sons, Ltd.