Structural characterisation by both positive- and negative-ion electrospray mass spectrometry of partially methyl-esterified oligogalacturonides purified by semi-preparative high-performance anion-exchange chromatography.
The off-line coupling of high-performance anion-exchange chromatography (HPAEC) to electrospray ionisation/ion trap mass spectrometry (ESI-ITMS) is described. The Dionex carbohydrate membrane desalter (CMD) has been assessed as an on-line chromatographic desalting system to remove the high sodium concentration necessary for the HPAEC separation of partially methyl-esterified oligogalacturonides. The developed HPAEC configuration proved to be suitable for indirect coupling with ESI-ITMS. This paper provides some interesting features of positive- and negative-ion multistage tandem mass spectrometry (MS(n)) analysis of these acidic oligosaccharides. The spectra acquired in both negative- and positive-ion modes show characteristic fragment ions resulting from glycosidic bond and cross-ring cleavages. Some new mass spectrometric fragmentation routes are also described. The positive-ion mode gave more complex spectra but was as informative as the negative-ion mode. ESI-ITMS was revealed to be, as previously reported from direct use on an unseparated enzymatic digest, a powerful sequencing technique for the determination of linkage type and the methyl ester distribution of partially methyl-esterified oligogalacturonides. Moreover, unlike matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-ToF MS), it gives valuable information on the elution behaviour of these oligomers in relation to their structure, namely the HPAEC co-elution of isomeric structures.
Quéméner
Bernard
B
Institut National de la Recherche Agronomique, Unité de Recherche sur les Polysaccharides, leurs Organisations et leurs Interactions (URPOI), rue de la Géraudière, BP 71627, 44316 Nantes, France. quemener@nantes.inra.fr
Désiré
Cédric
C
Lahaye
Marc
M
Debrauwer
Laurent
L
Negroni
Luc
L
D002852:Chromatography, Ion Exchange / Q000379:methods*; D004952:Esters / Q000737:chemistry; D007536:Isomerism; D008745:Methylation; D015394:Molecular Structure; D009844:Oligosaccharides / Q000032:analysis / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D004952:Esters; D009844:Oligosaccharides; C412763:oligogalacturonic acid