Electron capture dissociation of divalent metal-adducted sulfated oligosaccharides

κ-Carrageenan sulfated oligosaccharides containing one, two, and four sulfate groups were complexed with divalent metal cations and electrosprayed in positive ion mode. The resulting metal complexes were subjected to sustained off-resonance irradiation collision-activated dissociation (SORI-CAD) and electron capture dissociation (ECD). The presence of divalent metal cations in the electrospray solution facilitates formation of doubly positively charged precursor ions in the gas phase. Unsurprisingly, abundant sulfate group (SO3) loss is observed in SORI CAD of sulfated oligosaccharides complexed with divalent metal cations. By contrast, sulfation is retained in ECD of metal-sulfated oligosaccharide complexes, providing information on the site of sulfation. Most product ions resulting from ECD are C/Z- or B/Y-type ions, corresponding to cleavage of glycosidic bonds linking two sugar units. However, several A/X-type product ions corresponding to sugar cross-ring cleavage were also observed in ECD. Such cross-ring fragments are important in carbohydrate analysis because they provide linkage information.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (220 K)Download as PowerPoint slideResearch highlights▶ Sulfated oligosaccharide dications from divalent metal adduction. ▶ ECD yields extensive fragmentation with sulfate retention. ▶ CAD mainly results in sulfate loss, precluding sulfate localization.