Influence of the labeling group on ionization and fragmentation of carbohydrates in mass spectrometry

Abstract

The ionization and fragmentation behaviors of carbohydrate derivatives prepared by reaction with 2-aminobenzamide (AB), 1-phenyl-3-methyl-5-pyrazolone (PMP), and phenylhydrazine (PHN) were compared under identical mass spectrometric conditions. It has been shown that the intensities of signals in MS spectra depend on the kind of saccharides investigated and reducing end labels used. PMP sialyllactose, when ionized by ESI/MALDI, produced a mixture of ϩ ions. PMP-and reduced AB-sialyllactose produced only Y-type fragment ions under both MS/MS sources. In the electrospray ionization (ESI)-MS/MS spectrum of PHN-sialyllactose, abundant ions corresponded to B, Z cleavages and in its MALDI-MS/MS spectrum, the abundant ions were consistent with Y glycosidic cleavages with the concurrence of B, C, and cross-ring fragment ions. In the MALDI-MS spectra of oligosaccharides acquired immediately after derivatization, it was possible to detect only PHN derivatives. After purification, spectra of all three types of derivatives showed high signal-to-noise ratios with the most abundant ions observed for AB reduced saccharides. [M ϩ Na] ϩ ions were the dominant products and their fragmentation patterns were influenced by the type of the labeling and the kind of oligosaccharide considered. In the MALDI-PSD and -MS/MS spectra of AB-derivatized glycans, higher m/z fragment ions corresponded to B and Y cleavages and the loss of bisecting GlcNAc appeared as a weak signal or was not detected at all. Fragmentation patterns observed in the spectra of hybrid/complex PHN and PMP glycans were more comparable-higher m/z fragments corresponded to B and C glycosidic cleavages. For PHN glycans, the abundance of ions resulting from the loss of bisecting GlcNAc depended on the number of residues linked to the 6-positioned mannose. Also, PHN and PMP derivatives produced cross-ring cleavages with abundances higher than observed in the spectra of AB derivatized oligosaccharides. For high-mannose glycans, the most informative cleavages were provided by AB and PHN type of labeling. Glycosylation is also highly sensitive to alterations of cellular function, and altered protein glycosylation is diagnostic of a number of disease states including, for example, rheumatoid arthritis and cancer [3]. Therefore, the growing interest in understanding the biological functions of carbohydrates has stimulated the development of methods for their improved analysis.In order to detect saccharides by UV/fluorescence and also to ease their characterization by mass spectrometry (MS), introducing a chromophore into the molecules has received increasing attention. In this respect, a large number of derivatization procedures for mono-and oligosaccharides have been described in the literature, most of which have been detailed in a recent review [4]. For example, 2-aminoacridine (2-AMAC) as a sensitive fluorophore, has been used for the detection of monosaccharides, and of neutral and charged oligosaccharides by electrospray ionization (ESI) and matrix-

Tandem Mass Spectrometry of Tagged and Permethylated Polysaccharides

“…The challenges to polysaccharides determination are that the glycan-moiety has different chemical properties than proteins or nucleic acids (Forsberg et al, 2000;Faber et al, 2001;Lattová et al, 2005;Mischnick et al, 2005;Nielsen et al, 2010) and most of them are www.intechopen.com…”

Using a nanoelectrospray-differential mobility spectrometer-mass spectrometer system for the analysis of oligosaccharides with solvent selected control over ESI aggregate ion formation

“…Negative mode ESI offers ionization advantages for the analysis of glycans, however, positive mode ESI is also desirable due to its capability to generate different MS/MS glycan ion fragmentation than typically observed in negative mode ESI-MS/MS [17,18]. To improve positive mode ESI ionization of glycans, derivatization of glycans with molecules containing basic sites has been employed [19]. While this approach has been successful, it increases the complexity of sample preparation, such that many researchers have explored other means by which analysis of underivatized glycans can be performed in positive mode ESI [13,17,18,21].…”

Linkage and branch determination of N-linked oligosaccharides using sequential degradation/closed-ring chromophore labeling/negative ion trap mass spectrometry

“…In structural analysis of carbohydrates, native and derivatized oligosaccharides have been analyzed by MALDI [5][6][7][8][9][10][11][12][13][14]. Metal ion coordinated [15,16] or chemically derivatized [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] oligosaccharides have been used for ESI analysis. Among those approaches, the method based on MALDI time-of flight/time-offlight (TOF/TOF) tandem mass spectrometry provides good sensitivity and cross-ring cleavage because of the use of high-energy collision-induced dissociation (he-CID) [8 -14].…”