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Selective linkage detection of O ‐sialoglycan isomers by negative electrospray ionization ion trap tandem mass spectrometry
Author(s) -
Casal Enriqueta,
LebrónAguilar Rosa,
Moreno Francisco Javier,
Corzo Nieves,
QuintanillaLópez Jesús Eduardo
Publication year - 2010
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.4463
Subject(s) - chemistry , ion trap , tandem mass spectrometry , electrospray ionization , fragmentation (computing) , mass spectrometry , top down proteomics , quadrupole ion trap , ion , selected reaction monitoring , triple quadrupole mass spectrometer , electrospray , protein mass spectrometry , analytical chemistry (journal) , polyatomic ion , quadrupole , mass spectrum , collision induced dissociation , chromatography , organic chemistry , atomic physics , computer science , operating system , physics
Sialylated O ‐linked oligosaccharides are involved in many biological processes, such as cell‐cell interactions, cell‐substance adhesion, and virus‐host interactions. These activities depend on their structure, which is frequently determined by tandem mass spectrometry. However, these spectra are frequently analyzer‐dependent, which makes it difficult to develop widely applicable analytical methods. In order to deepen the origin of this behavior, two couples of isomers of sialylated O ‐linked oligosaccharides, NeuAcα2‐3Galβ1‐3GalNAc‐ol/Galβ1‐3(NeuAcα2‐6)GalNAc‐ol and NeuGcα2‐3Galβ1‐3GalNAc‐ol/Galβ1‐3(NeuGcα2‐6)GalNAc‐ol, were analyzed by liquid chromatography/negative electrospray ionization ion trap tandem mass spectrometry (LC/ESI(−)‐MS n ) using both an ion trap and a triple quadrupole mass spectrometer. Results clearly showed that while ions obtained in the triple quadrupole instrument fitted very well with the standard fragmentation routes, in the ion trap several intense ions could not be explained by these rules, specially a fragment at m/z 597. Furthermore, this ion was observed in the mass spectrum of those isomers that sialic acid binds to GalNAc by an α 2‐6 linkage. From the MS 3 spectrum of this ion an unexpected structure was deduced, and it led to propose alternative fragmentation pathways. Molecular mechanics calculations suggested that the found atypical route could be promoted by a hydrogen bond located only in α 2‐6‐linked oligosaccharides. It has also been demonstrated that this process follows a slow kinetic, explaining why it cannot be observed using an ion beam‐type mass analyzer. In conclusion, ion traps seem to be more appropriate than triple quadrupoles to develop a reliable analytical method to distinguish between isomeric O ‐linked glycans. Copyright © 2010 John Wiley & Sons, Ltd.