Evidence for long-range glycosyl transfer reactions in the gas phase

Abstract

A long-range glycosyl transfer reaction was observed in the collision-induced dissociation Fourier transform (CID FT) mass spectra of benzylamine-labeled and 9-aminofluorene-labeled lacto-N-fucopentaose I (LNFP I) and lacto-N-difucohexaose I (LNDFH I). The transfer reaction was observed for the protonated molecules but not for the sodiated molecules. The long-range glycosyl transfer reaction involved preferentially one of the two L-fucose units in labeled LNDFH I. CID experiments with labeled LNFP I and labeled LNFP II determined the fucose with the greatest propensity for migration. Further experiments were performed to determine the final destination of the migrating fucose. , and post-translational protein modification [6 -8]. Whereas the insight into the physical process of carbohydrate recognition is in its infancy, considerable progress has been made towards the quantitation and structural elucidation of biologically active oligosaccharides. NMR [9] yields structural information about oligosaccharides. Frequently, however, an inherent problem is the limited amount of sample causing NMR experiments to become time-consuming or impossible. The sensitivity and accuracy of mass spectrometry has made this technique the best choice for analysis of oligosaccharides [10,11]. Structural information can be derived from collision-induced dissociation (CID) [12][13][14][15][16][17][18][19][20] or from post-source decay (PSD) time-of-flight (TOF) experiments [21][22][23][24][25][26]. Fragmentation of glycosidic bonds provides information about the monosaccharide sequence and computer algorithms can extract sequence information from web-based catalogs of MS n spectra [27]. However, the assignment of anomeric configuration [28 -35] and linkage [18, 36 -38] within the oligosaccharide structure is not a trivial task. Glycosidase digestion [13, 39 -47] in conjunction with mass spectrometric analysis can be used to assign linkage and stereochemistry. In an alternative approach, CID-fragmentation patterns have been linked to structural motifs in the oligosaccharide (catalog library approach) [12].We recently reported on the use of more nucleophilic benzylogous amines, such as benzylamine and 9-aminofluorene, for the labeling of oligosaccharides and the experimental results of FT-MS experiments with the labeled oligosaccharides [48]. Detection of 5 pmol of 9-amino fluorene-labeled oligosaccharide was achieved with a photo diode array during HPLC separation. The label combines low cost with good nucleophilicity and ease of introduction. The behavior of oligosaccharides derivatized with benzylogous amines such as benzylamine in CID experiments has not been reported, although data obtained from PSD matrix-assisted laser desorption/ionization (MALDI)-TOF experiments have been published [25,49].In this paper, we discuss a long-range glycosyl transfer that occurs during CID for benzylamine-and 9-AmFL-labeled oligosaccharides. The transfer of a fucose across three monosaccharide units was observed only in protonated molecules. To t...

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update covering the period 2001–2002

“…It involves initial protonation of the derivative, presumably on the amine group linking the carbohydrate and derivative. Similar fucose migrations have been reported in the CID spectra of protonated benzylamine-(2/9) and 9-aminofluorene-(7) labeled carbohydrates (Franz & Lebrilla, 2002). These rearrangement ions are absent from the fragmentation spectra of sodiated ions (Franz & Lebrilla, 2002;Harvey et al, 2002), emphasizing the advantage of using alkali metalcatonized ions in investigations of the structure of new compounds.…”

Mass spectrometric glycan rearrangements

“…Haverkamp and co-workers demonstrated that CID of sodiated precursor ions ([M þ Na] þ ) did not yield any product ions that involved the loss of an internal residue (Kováčik et al, 1995;Brüll et al, 1998). Identical observations were reported from CID-experiments performed in a matrix-assisted laser desorption ionization (MALDI) Fourier transform ion cyclotron resonance (FTICR) system by Franz and Lebrilla (2002): lacto-N-fucopentaose I labeled with benzylamine (BA) yielded product ions with IRL only after fragmentation of the protonated precursor ion, and not with the sodiated analogue (Fig. 2).…”

“…As mentioned earlier, the rearrangement process is often described as the loss of an internal residue (moiety B), or alternatively as the transfer or migration of a monosaccharide (e.g., transfer of A À C). Next to the loss of a single internal residue, rearrangements have been reported which involve the loss of multiple internal residues (Ernst, Müller, & Richter, 1997;Franz & Lebrilla, 2002;Broberg, 2007). In these cases, transfer is often the preferred term, as in the case of long-distance migration observed in fucose (Fuc) rearrangements (see Section VII).…”

“…Red triangle, Fuc; yellow circle, Gal; blue square, GlcNAc; blue circle, glucose; BA, benzylamine. Taken from Franz and Lebrilla (2002) with permission from Elsevier. FIGURE 3.…”

Sequencing of oligosaccharides derivatized with benzylamine using electrospray ionization‐quadrupole time of flight‐tandem mass spectrometry

“…The fragmentation pattern was dominated by fragment ions retaining the modified reducing terminus, thus simplifying the interpretation of the mass spectral data. More recently, the behavior of oligosaccharides derivatized with benzylamine in CID Fourier transform experiments has been reported [44]. In addition, derivatization of oligosaccharides with benzylamine was also used in a capillary electrophoretic method for the separation of oligosaccharides [45].…”