Characterization of oligosaccharide composition and structure by quadrupole ion trap mass spectrometry

Abstract

The use of electrospray ionization-quadrupole ion trap mass spectrometry for the characterization of linear oligosaccharides and N-linked protein oligosaccharide mixtures is described. Tandem mass spectrometry (MS/MS) experiments with orders higher than two offer a number of ways to enhance MS/MS spectra and to derive information not present in MS and MS2 spectra. Three such methods are presented in this paper. (a) Collisional activation of permethylated oligosaccharide molecular ions (MS2) as illustrated by maltoheptaose, produces abundant fragments from glycosidic bond cleavages which indicate composition and sequence, and weak cross-ring cleavage products which denote specific linkages within the oligosaccharide. Through the trapping and further dissociation of these fragments (MSn), cross-ring cleavage products can be confirmed and their relative abundances increased to facilitate interpretation. (b) The mechanisms of formation of two isobaric ions or ions isobaric with another ion's isotope peaks, such as those present in the MS2 spectrum of the ribonuclease B oligosaccharide GlcNAc2-Man5 can be independently established by separate MS3 experiments. (c) Ions in the MS2 spectrum, specific for individual components of an isobaric mixture, can be isolated and characterized by further stages of fragmentation. This is illustrated by two isobaric oligosaccharides from chicken ovalbumin of the composition HexNAc5Hex5. These findings indicate the utility of ion trap mass spectrometry towards the facile determination of oligosaccharide composition, sequence, branching and linkage, providing a wealth of structural information not obtainable by other individual methods of carbohydrate mass spectrometric analysis.

Carbohydrate Structural Isomers Analyzed by Sequential Mass Spectrometry

“…6 In both cases, however, the product structures remain to be characterized. A large body of work has shown that spectral comparisons of isomers at different stages of sequential molecular fragmentation (MS n ) [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] are clearly different, although in one case, reproducibility has been reported to be "vague". 25 In our experience, spectral reproducibility has been excellent, 26 and this very feature has provided an opportunity to build a searchable fragment library 27 and derive glycan structure with supporting tools.…”

Identification of isomeric N-glycan structures by mass spectrometry with 157 nm laser-induced photofragmentation

“…Different combinations of ionization techniques, ion activation, and mass analyzers have been used, including fast atom bombardment (FAB)-MS [10 -12], infrared-laser desorption MS [13,14], matrix-assisted laser desorption/ionization (MALDI)/magnetic sector MS [15][16][17], electrospray ionization (ESI)-MS [18,19], MALDI/time-offlight (TOF)-MS [20 -22], ESI ion-trap MS [23][24][25], MALDI Fourier transform MS [26], ESI-or MALDIbased quadrupole/TOF-MS [27][28][29][30], MALDI/Postsource Decay (PSD) TOF-MS [31][32][33], and, more recently, MALDI-TOF/TOF-MS [34 -38].…”

Gas-phase oligosaccharide nonreducing end (GONE) sequencing and structural analysis by reversed phase hplc/mass spectrometry with polarity switching

“…TOF/TOF or Q-TOF mass spectrometers have been widely used in tandem MS characterization of oligosaccharides. In contrast to such tandem-in-space types of instruments, where tandem MS is limited to a MS 2 stage (not including in-source fragmentation), ion storage devices, such as ion trap mass spectrometers, allow multi-stage activations of the parent oligosaccharide ions into successive fragment ions [13,[47][48][49]. Sequential fragmentation, analogous to successive enzyme treatment in the classic sequencing technique, is thus possible with ion trap instruments.…”