Infrared Multiphoton Dissociation Mass Spectrometry for Structural Elucidation of Oligosaccharides (original) (raw)
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Analytical Chemistry, 2006
The structural elucidation of oligosaccharides remains a major challenge. Mass spectrometry provides a rapid and convenient method for structural elucidation based on tandem mass spectrometry. Ions commonly are selected and subjected to collision-induced dissociation (CID) to obtain structural information. Unfortunately, N-linked oligosaccharides are relatively large compounds and are not readily fragmented using CID. In this report, we illustrate the use of infrared multiphoton dissociation (IRMPD) to obtain structural information for large Nlinked oligosaccharides. The IRMPD and CID behavior of oligosaccharides were compared for high-mannose-type oligosaccharides. Fragmentation that could not be obtained through conventional CID in Fourier transform ion cyclotron resonance mass spectrometry was observed with N-linked oligosaccharides. O-Linked and N-linked glycans of similarly large sizes were compared. It was found that internal cross-ring cleavages were observed only for N-linked oligosaccharides. The mannose branch points of N-linked oligosaccharides are apparently more susceptible to cross-ring cleavages.
Analytica Chimica Acta, 2014
Carbohydrates display a wide variety of structures, which complexity and heterogeneity obviously challenge the field of analytical chemistry. Tandem mass spectrometry, with its remarkable sensitivity and high information content, provides key advantages to address the structural elucidation of polysaccharides. Yet, classical fragmentation by collision-activated dissociation (CAD) fails in many cases to reach a comprehensive structural determination, especially when isomers have to be differentiated. In this work, for the first time, Vacuum Ultra-Violet (VUV) synchrotron radiation is used as the activation process in tandem mass spectrometry of large oligosaccharides. Compared to low energy CAD (LE-CAD), photon activated dissociation brought more straightforward and valuable structural information. Outstanding feature was that complete series of informative ions were produced, exhibiting minor neutral losses. Moreover, systematic fragmentation rules could be drawn, thus facilitating the definitive assignments of fragments identities. As a result, most of the structures present in a complex mixture of oligogalacturonans could be comprehensively resolved, including many isomers differing in the positioning of methyl groups along the galacturonic acid backbone, which confers different properties and end-uses to these molecules.
Rapid Communications in Mass Spectrometry, 2013
RATIONALE: Carbohydrates have essential functions in living organisms and cells, but, due to the presence of numerous linkage combinations, substituent sites and possible conformations, they are the class of biomolecules which exhibits the huge structural diversity found in nature. Thereby, due to such diversity and poor ionization, their structural deciphering by mass spectrometry is still a very challenging task. METHODS: Here, we studied a series of linear and cyclic neutral oligosaccharides using electrospray with collision-induced dissociation (CID), pulsed-Q-dissociation (PQD) and the higher-energy C-trap dissociation (HCD) feature of a linear ion trap Orbitrap hybrid mass spectrometer (LTQ-Orbitrap). The collision energy necessary to obtain 50% fragmentation (CE 50 values) in CID, PQD and HCD was used to correlate both size and structures. RESULTS: The default settings for activation time and/or activation Q are the most appropriate, except for HCD, where 100 ms instead of 30 ms gave more intense fragment ions. PQD exhibits a 2-8-fold lower sensitivity than CID. HCD provides signals closer or slightly superior by 1.5-fold than PQD, and offers a more balanced ion distribution through the spectrum. Furthermore, HCD offers the possibility to make fine adjustments of the energy via the eV scale to further increase the yield of low-mass fragments. CONCLUSIONS: The complementarity of CID, PQD and HCD was clearly demonstrated by obtaining structural information on hexa-, hepta-and octasaccharides. Together, these results clearly indicate the usefulness of the CID/HCD pair for further structural deciphering, and analysis of more complex structures such as multi-antennary carbohydrates or glycoconjuguates alone or in mixture.
Journal of Mass Spectrometry, 2000
A study of the collision-induced dissociation post-source decay (PSD) spectra of free oligosaccharides is presented. These spectra, when obtained with helium as collision gas, show 1,5 X fragments containing the reducing end sugar. The presence of these fragments permits Y ions and, consequently, B and C peaks to be identified. This is a common behaviour from which it has been possible to delineate a general method for the easy assignment of the peaks in PSD spectra of underivatized neutral sugars, allowing the sequence of a real unknown to be obtained. Scheme 1. Oligosaccharide fragmentation nomenclature for peaks produced by a single fragmentation (from Ref. 21). Subscripts indicate the positions relative to the termini analogous to the system used in peptides, and superscripts indicate cleavages within carbohydrate rings.
Rapid Communications in Mass Spectrometry, 2009
Glycans exist as part of glycoproteins and glycolipids, which are involved in a variety of biological functions. The analysis of glycan structures, particularly that of structural isomers, is fundamentally important since isomeric glycans often show distinct functions; however, a method for their structural elucidation has not yet been established. Anomeric configurations, linkage positions and branching are the major factors in glycans and their alteration results in a large diversity of glycan structures. The analysis of vicinally substituted oligosaccharides is extremely difficult because the product ions formed in tandem mass spectrometry (MS/MS) often have the same m/z values. In our endeavor to address the issue, we analyzed a series of homo-substituted trisaccharides consisting only of glucose by collision-induced dissociation (CID), especially energy-resolved mass spectrometry (ERMS). It was found that these structurally related glycans could be distinguished by taking advantage of differences in their activation energies in ERMS.
Journal of the American Society for Mass Spectrometry
The connection between monosaccharides influences the structure, solubility, and biological function of carbohydrates. Although tandem mass spectrometry (MS/MS) often enables the compositional identification of carbohydrates, traditional MS/MS fragmentation methods fail to generate abundant cross-ring fragments of intrachain monosaccharides that could reveal carbohydrate connectivity. We examined the potential of helium-charge transfer dissociation (He-CTD) as a method of MS/MS to decipher the connectivity of β-1,4and β-1,3-linked oligosaccharides. In contrast to collision-induced dissociation (CID), He-CTD of isolated oligosaccharide precursors produced both glycosidic and cross-ring cleavages of each monosaccharide. The radical-driven dissociation in He-CTD induced single cleavage events, without consecutive fragmentations, which facilitated structural interpretation. He-CTD of various standards up to a degree of polymerization of 7 showed that β-1,4and β-1,3-linked carbohydrates can be distinguished based on diagnostic 3,5 A fragment ions that are characteristic for β-1,4-linkages. Overall, fragment ion spectra from He-CTD contained sufficient information to infer the connectivity specifically for each glycosidic bond. When testing He-CTD to resolve the order of β-1,4and β-1,3-linkages in mixed-linked oligosaccharide standards, He-CTD spectra sometimes provided less confident assignment of connectivity. Ion mobility spectrometry−mass spectrometry (IMS−MS) of the standards indicated that ambiguity in the He-CTD spectra was caused by isobaric impurities in the mixed-linked oligosaccharides. Radical-driven dissociation induced by He-CTD can thus expand MS/MS to carbohydrate linkage analysis, as demonstrated by the comprehensive fragment ion spectra on native oligosaccharides. The determination of connectivity in true unknowns would benefit from the separation of isobaric precursors, through UPLC or IMS, before linkage determination via He-CTD.
Carbohydrate Research, 1993
Homo-and hetero-o&saccharides l-27, composed of hexopyranose, deoxyhexopyranose, deoxyfluorohexopyranose, and Zacetamido-2deoxyhexopyranose units, have been examined by fast-atombombardment mass spectrometry. Scans by finked magnetic and electrostatic (B/E) fields of quasimolecular [M + HI+ ions, or scans combined with helium collision, gave rise to structurally significant ions. The information thus obtained aids significantly in the sequence analysis of oligosaccharides without derivatization. INTRODUCPION Mass spectrometry plays an important role in structural analysis of complex carbohydrates. The available methods, which involve the ionization in the gas phase, e.g., electron-impact (ED and chemical-ionization (CI) mass spectrometry, provide useful information for the confirmation of structures of substances that are sufficiently volatile or mixtures of substances amenable to gas-liquid or liquid chromatography. The low volatility of many substances makes their analysis by mass spectrometry impractical and requires prior chemical manipulation to produce a sufficiently volatile material. Such procedures may be difficult to apply with substances that are unstable or undergo side reactions or are available in only minute amounts.
Analytical Chemistry, 2006
Variation in the wavelength of irradiation in infrared multiple-photon dissociation (IR-MPD) of lithium-tagged glucose-containing disaccharide ions (1-2-, 1-3-, 1-4-, and 1-6-linked isomers of both anomeric configurations) resulted in marked differences in their mass spectral fragmentation patterns. Two-dimensional plots of the fragment yield versus infrared wavelength for each mass spectral product ion were unique for each isomer and can be considered a spectral fingerprint. Individual product ions or diagnostic ratios of key product ions can be optimized at specific IR wavelengths. The technique permits both linkage position and anomeric configuration to be assigned. The ratio of the fragments derived by cleavage at the glycosidic bond (m/z 169/187) is much enhanced for-anomers compared to r-anomers. Differences in the diagnostic product ions 169 and 187 were largest in the range of 9.0-9.4 µm, where the maximum dissociation yield was observed. Conversely, at 10.6 µm, the wavelength of nontunable CO 2 lasers that accompany commercial Fourier transform ion cyclotron resonance mass spectrometers, the dissociation yield was poor and anomeric differentiation was not possible. In contrast to previous studies by collision-induced dissociation, the trends in dissociation behavior between anomers using IR-MPD are significant and allow simple diagnostic rules to be established. By depositing energy into these isobaric ions via narrow-band IR excitation, the resulting internal energy can be finely controlled, thereby obtaining high reproducibility in dissociation patterns. Given the multidimensionality of variable-wavelength IR-MPD of lithiated disaccharides, it is expected that this approach can overcome some of the current limitations in isomer differentiation.