Sulfate migration in oligosaccharides induced by negative ion mode ion trap collision‐induced dissociation

Abstract

Migration of sulfate groups between hydroxyl groups was identified after collision-induced dissociation (CID) of sulfated oligosaccharides in an ion trap mass spectrometer in negative ion mode. Analysis of various sulfated oligosaccharides showed that this was a common phenomenon and was particularly prominent in sulfated oligosaccharides also containing sialic acid. It was also shown that the level of migration was increased when the sulfate was positioned on the flexible areas of the oligosaccharides not involved in the pyranose ring, such as the extra-cyclic C-6 carbon of hexoses or N-acetylhexosamines, or on reduced oligosaccharide. This suggested that migration is dependent on the spatial availability of the sulfate in the ion trap during collision. It is proposed that the migration is initiated when the negatively charged -SO3 (-) residue attached to the oligosaccharide precursor becomes protonated by a CID-induced proton transfer. This is supported by the CID fragmentation of precursor ions depleted of acidic protons such as doubly charged [M - 2H](2-) ions or the sodiated [M + Na - 2H](-) ions of oligosaccharides containing one sulfate and one sialic acid in the same molecule. Compared to the CID fragmentation of their monocharged [M - H](-) ions, no migration was observed in CID of proton depleted precursors. Alternative fragmentation parameters to suppress migration of sulfated oligosaccharides also showed that it was not present when sulfated oligosaccharides were fragmented by HCD (High-Energy C-trap Dissociation) in an Orbitrap mass spectrometer.

Chip‐based high resolution tandem mass spectrometric determination of fibroblast growth factor—chondroitin sulfate disaccharides noncovalent interaction

“…Given the ergodic nature of CID process, rearrangements in the collision cell, implying SO 3 − migration, were observed in some instances and were reported by McClellan et al and Kenny et al However, our previous MS/MS experiments performed on commercially available CS/DS having the sulfate position specified by the producer have shown that, by applying the fragmentation protocol developed by us , , , which was also used in the present study, such rearrangements and SO 3 − migration did not occur in CID MS/MS.…”

In-Depth Characterization of N-Linked Oligosaccharides Using Fluoride-Mediated Negative Ion Microfluidic Chip LC–MS

“…Secondly, monosaccharide rearrangements during CID fragmentation observed in positive ESI have generally not been seen for negative ESI [19]. Migration of sulfate was recently reported using a linear ion trap; however, the migration appeared to be overcome when converting from CID to HCD fragmentation [29]. On the other hand, the overall sensitivity in the negative ion mode is found to be lower than in the positive ion mode for neutral glycans [30]; however, higher sensitivity in the negative ion mode can be observed for negatively charged glycans, e.g.…”

Characterization of Glycan Structures of Chondroitin Sulfate-Glycopeptides Facilitated by Sodium Ion-Pairing and Positive Mode LC-MS/MS

“…The 13 deduced structures (Table 1), presented here and in our previous publication [22], may also be present in the CS structures of additional CS proteoglycans, and should thus be looked for in future CS glycoproteomic studies. The use of Na + ion-pairing to sulfated glycans has previously been used to protect sulfated glycans from decomposing and/or rearranging during collisional activation, mainly in negative mode MS/MS [20, 40, 41]. We now show that the addition of Na + ions may be beneficial for studies of sulfated glycopeptides also in positive mode LC-MS/MS setups.…”