Matrix-assisted laser desorption/ionisation mass spectrometry for the direct analysis of enzymatically digested kappa- iota- and hybrid iota/nu-carrageenans

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 inten...

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Bibliographic Details
Published in:Rapid communications in mass spectrometry 2005-01, Vol.19 (16), p.2217-2226
Main Authors: Antonopoulos, Aristotelis, Hardouin, Julie, Favetta, Patrick, Helbert, William, Delmas, Agnès F., Lafosse, Michel
Format: Article
Language:English
Subjects:
Carrageenan - chemistry
Carrageenan - metabolism
Molecular Structure
Oligosaccharides - analysis
Oligosaccharides - chemistry
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
Stereoisomerism
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Summary: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 Ca2+, were also observed. Copyright © 2005 John Wiley & Sons, Ltd.
ISSN:0951-4198
1097-0231
DOI:10.1002/rcm.2051