Differentiation of Isomers by Wavelength-Tunable Infrared Multiple-Photon Dissociation-Mass Spectrometry: Application to Glucose-Containing Disaccharides (original) (raw)
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Analytical Chemistry, 2011
I somers remain a problem in mass spectrometry, especially closely related isomers that yield very similar ratios of product ions upon unimolecular dissociation. This situation is frequently encountered among isomers varying in their stereochemistry at one or more positions (e.g., carbohydrates and glycoconjugates 1À3), positional isomers (e.g., phospholipids, di-and triacylglycerols 4À6), and isomers varying in the nature of double bonds (cis or trans or multiple double bonds, as in various lipids, wax esters, hydrocarbons, and other compounds 7À9). The problem has been approached in different ways, some more successful than others, depending on the nature of the precursor ions. Use of differences in fragmentation patterns after collision-induced dissociation (CID) is still the most common and well-studied approach. 1À3,5À7,9,10 Other techniques exploit differences in physical properties of isomeric ions: migration rates of ions through a neutral gas (ion mobility spectrometry), 11,12 reactivities of ions, 13,14 charge exchange MS, 15,16 direct photon absorption or emission, 17,18 variable wavelength photodissociation in the infrared, 19À23 visible 24 or ultraviolet 25 with one or more 26,27 lasers, differences in photodissociation by rapid pulse shaping over an approximate Gaussian wavelength distribution centered at 800 nm, 28,29 and relatively high-resolution spectroscopy
Analytical Chemistry
The vast array of molecular isomerisms which form the complex molecular structure of carbohydrates is the foundation of their biological versatility but defies the analytical chemist. Hyphenations of mass spectrometry with orthogonal structural characterization, such as ion mobility or ion spectroscopy, have recently shown great promise for distinction between closely related molecular structures. Yet, the lack of analytical strategies for identification of isomers present in mixtures remains a major obstacle to routine carbohydrate sequencing. In this context, an ideal workflow for glycomics would combine isomer separation and individual characterization of the molecular structure with atomistic resolution. Here we report the implementation of such a multidimensional analytical strategy, which consists of the first online coupling of high-performance liquid chromatography (HPLC)−MS and infrared multiple photon dissociation (IRMPD) spectroscopy. The performance of this novel workflow is exemplified in the case of monosaccharides (anomers) and disaccharides (regioisomers) standards. We report that the LC−MS-IRMPD approach offers a robust advanced MS diagnostic of mixtures of isomers, including carbohydrate anomers, which is critical for carbohydrate sequencing. Our results also explain the bimodal character generally observed in LC chromatograms of carbohydrates. More generally, this multidimensional analytical strategy opens the gateway to rapid identification of molecular isoforms with potential application in the "omics" fields.
Infrared Multiphoton Dissociation Mass Spectrometry for Structural Elucidation of Oligosaccharides
Glycomics, 2008
The structural elucidation of oligosaccharides remains a major challenge. Mass spectrometry provides a rapid and convenient method for structural elucidation on the basis of tandem mass spectrometry. Ions are commonly selected and subjected to collision-induced dissociation (CID) to obtain structural information. However, a disadvantage of CID is the decrease in both the degree and efficiency of dissociation with increasing mass. In this chapter, we illustrate the use of infrared multiphoton dissociation (IRMPD) to obtain structural information for O-and N-linked oligosaccharides. The IRMPD and CID behaviors of oligosaccharides are compared.
The Journal of Organic Chemistry, 1992
Fast atom bombardment ionization followed by tandem mass spectrometry of 'Boand 2H-labeled dilithiated disaccharides is used to differentiate the linkage position of three isomeric disaccharides. The mechanisms of dissociation proposed are based on the mass spectrometry, experimental data, and semiempirical calculations, the latter of which provide information on the stability of the deprotonated dilithiated precursor, (M + 2Li -H)+. Tandem mass spectrometry experiments indicate that, as in the case of monolithiated disaccharides, reducing ring opening occurs followed by two-, three-, and four-carbon chain neutral losses. Semiempirical calculations support the experimental data which suggest that one lithium is tetracoordinate between the two sugar rings, while the second lithium is dicoordinate forming a lithium alkoxide with one of the deprotonated hydroxyl groups of the reducing ring.
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.
RATIONALE: The structural characterization of unknown oligosaccharides remains a big challenge since a large number of isomeric structures are possible even for disaccharides. In this work, electrospray ionization collision-induced dissociation tandem mass spectrometry (ESI-CID-MS/MS) was used for the differentiation of isomeric pentose disaccharides, a-(1 ! 5)-L-arabinobiose (Ara 2) and b-(1 ! 4)-D-xylobiose (Xyl 2). METHODS: ESI-MS/MS spectra of [M + Li] + and [M + Na] + ions of Ara 2 and Xyl 2 , as well as these precursor ions of 18 O-labelled disaccharides, were acquired using two mass spectrometers equipped with different analyzers: LIT (linear ion trap) and Q-TOF (quadrupole time-of-flight). RESULTS: Product ions observed in MS/MS spectra arise from the cleavage at the nonreducing side of the glycosidic bond (Y 1 +) and from cross-ring cleavages 0,1 A 2 + , 0,2 A 2 + , and 0,3 A 2 + at the reducing residue. Statistically significant differences were observed between the relative abundance of specific product ions, when comparing both disaccharides. These differences allowed discriminant models to be built and to propose a criterion using the relative abundances of selected ions capable of discriminating between the isomers for both adduct ions and spectrometers. CONCLUSIONS: Isomeric pentose disaccharides can be distinguished based on the fragmentation of both [M + Li] + and [M + Na] + ions and using different mass spectrometers. However, LIT instrument has a better discriminant power. Oligosaccharides are an important class of biomolecules present in living systems, most of them covalently linked to proteins and lipids forming glycoproteins and glycolipids, respectively. The oligosaccharide moieties play a key role in several biological processes, such as molecular recognition, cell-cell interaction, and stabilization of protein conformations, among others. [1,2] Also, changes in their structures have been observed in a variety of diseases, namely breast cancer. [3] Oligo-and polysaccharides are important from biological point of view, but also in many industrial applications. [4-6] The knowledge of their structures is essential for understanding their biological functions and properties. Mass spectrometry (MS) with electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI) combined with tandem mass spectrometry (MS/MS or MS n), [7,8] in which the fragmentation of the precursor ion is usually achieved by collision-induced dissociation (CID), [9] has been widely used with success in structural analysis of oligo-and polysaccharides. [10-17] Due to their structural complexity, polysaccharides are usually degraded into oligosaccharides by controlled chemical or enzymatic hydrolysis prior to MS analysis. [10-15] Due to the isomeric nature of monosaccharides, and the presence of different possible linkage positions and anomeric configurations (a or b), a large number of isomeric structures are possible even for the simplest oligosaccharides, the disaccharides. Thus, the structural characterization of unknown oligosaccharides remains a big challenge. The differentiation of isomeric standard oligosaccharides has been achieved based on differences in their fragmentation profile. Using CID-MS/MS spectra of sodium ([M + Na] +) and lithium ([M + Li] + and [M + 2Li À H] +) adduct ions, it was possible to identify the linkage position of glucose disaccharides. [18-20] Infrared multiple-photon dissociation of [M + Li] + ions was also used with the same purpose. [21,22] The distinction of their anomeric configuration was obtained by CID-MS/MS analysis of [M + Na] + and [M + Li] + ions. [23,24] In negative mode conditions, the differentiation of both linkage position and anomeric configuration of glucose disaccharides was achieved based on the fragmentation pattern of their [M-H]-ions. [25] Disaccharide isomers with different linkage types and different monosaccharide residues at the non-reducing end (galactose, glucose or mannose) were also differentiated by CID-MS/MS of their [M + Na] + ions. [26] The distinction between isomeric disaccharides composed of glucose and fructose differing in the glycosidic linkage position was achieved by CID-MS/MS of their [M + Pb À H] + ions. [27] Also, the assignment of the stereochemistry and anomeric configuration of hexose disaccharides was proposed based on MS 3 data. [28-31] For all the cited studies, it is worth pointing out that * Correspondence to: M. R. M. Domingues, Mass
Rapid Communications in Mass Spectrometry, 2004
The spectra recorded by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS/MS) of complex carbohydrates from human milk are presented. Besides ions originating from glycosidic cleavages and from sugar ring fragmentations, these spectra show intense peaks that may be assigned to ions produced by three new fragmentation pathways involving a six-atom rearrangement. These ions, together with the A fragments from sugar ring fragmentations, open the possibility of obtaining a complete mapping of the linkage positions present in the carbohydrates investigated by MALDI-TOF/TOF. Copyright © 2004 John Wiley & Sons, Ltd.
Journal of Mass Spectrometry, 2004
An atmospheric pressure (AP) infrared (IR) laser ionization technique, implemented on a quadrupole ion trap mass spectrometer, was used to analyze underivatized, N-linked oligosaccharides in solution. Experiments were conducted on an atmospheric pressure infrared ionization from solution (AP-IRIS) ion source which differed from previous AP IR matrix-assisted laser desorption/ionization (MALDI) interfaces in that the ion source operated in the absence of an extraction electric field with a higher power 2.94 µm IR laser. The general term 'IRIS' is used as the mechanism of ionization differs from that of MALDI, and is yet to be fully elucidated. The AP-IRIS ion source demonstrated femtomole-level sensitivity for branched oligosaccharides. AP-IRIS showed ∼16 times improved sensitivity for oligomannose-6 and the core-fucosylated glycan M3N2F over optimal results obtainable on a AP UV-MALDI with a 2,4,6trihydroxyacetophenone matrix. Comparison between IR and UV cases also showed less fragmentation in the IR spectrum for a glycan with a conserved trimannosyl core, core-substituted with fucose. A mixture of complex, high-mannose and sialylated glycans resulted in positive ion mass spectra with molecular ion peaks for each sugar. Tandem mass spectrometry of the sodiated molecular ions in a mixture of glycans revealed primarily glycosidic (B, Y) cleavages. The reported results show the practical utility of AP-IRIS while the ionization mechanism is still under investigation.
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.