Laser‐induced photofragmentation of neutral and acidic glycans inside an ion‐trap mass spectrometer

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The fragmentation of 5-hydroxy-6-glutathionyl-7,9,11,14-eicosatetraenoic acid [leukotriene C 4 or LTC 4 (5, 6)] and its isomeric counterpart LTC 4 (14, 15) were studied by low and high-energy collisional induced dissociation (CID) and 157 nm photofragmentation. For singly charged protonated LTC 4 precursors, photodissociation significantly enhances the signal intensities of informative fragment ions that are very important to distinguish the two LTC 4 isomers and generates a few additional fragment ions that are not usually observed in CID experiments. The ion trap enables MS n experiments on the fragment ions generated by photodissociation. Photofragmentation is found to be suitable for the structural identification and isomeric differentiation of cysteinyl leukotrienes and is more informative than low or high-energy CID. We describe for the first time the structural characterization of the LTC 4 (14, 15) isomer by mass spectrometry using CID and 157 nm light activation methods. (J

supporting

confidence: 80%

Section: Mass Spectrometrymentioning

confidence: 99%

Structural analysis of leukotriene C₄isomers using collisional activation and 157 nm photodissociation

Devakumar

O'Dell

Walker

et al. 2008

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“…Whereas high photon energy [20,22] enables the photofragmentation of native oligosaccharides, derivatization with a fluorophore is used for visible and near UV photofragmentation of oligosaccharides [21,23]. To delineate the wavelength ranges that could be used in the near UV range to fragment acidic oligosaccharides, we recorded the first gas-phase optical spectra as a function of laser wavelength for three heparin-derived disaccharides.…”

Section: Resultsmentioning

confidence: 99%

Wavelength-tunable ultraviolet photodissociation (UVPD) of heparin-derived disaccharides in a linear ion trap

Racaud

Antoine

Joly

et al. 2009

A set of three heparin-derived disaccharide deprotonated ions was isolated in a linear ion trap and subjected to UV laser irradiation in the 220 -290 nm wavelength range. The dissociation yields of the deprotonated molecular ions were recorded as a function of laser wavelength. They revealed maximum absorption at 220 nm for the nonsulfated disaccharide, but centered at 240 nm for the sulfated species. The comparison of the fragmentation patterns between ultraviolet photodissociation (UVPD) at 240 nm and CID modes showed roughly the same distribution of fragment ions resulting from glycosidic bond cleavages. Interestingly, UVPD favored additional cross ring cleavages of A and X type ion series enabling easier sulfate group location. It also reduced small neutral losses ( T he major advances achieved in mass spectrometry have revolutionized the structural analysis of proteins and led to the emergence of proteomic strategies. Although software-assisted de novo sequencing of peptides resulting from unknown proteins has become a routine task, the structural assignment of complex N-and O-glycans is much less trivial. Unlike proteins accurately translated from a unique template that follows a universal code, a similar set of glycosyl transferases may, across different species, build oligosaccharides of different structure according to an a priori unpredictable chronological catalysis activity.Compared with N-and O-linked glycans, the issue of structural complexity is continuing to increase in the world of glycosaminoglycans. Glycosaminoglycans are linear polymerized disaccharidic repeating units containing hexuronic acids and hexosamines. Their essential roles in governing numerous biologic functions [1] have led many groups to focus their efforts on defining generic strategies based on mass spectrometry, to obtain the structural definition of these acidic oligosaccharides. In the case of oligosaccharides derived from heparin or heparane sulfate, both glucuronic and iduronic acids and glucosamine may be sulfated at their OH and NH 2 groups. The fragmentation behavior of heparin-derived oligosaccharides has proven to be difficult to predict. Sulfate groups often impede access to exhaustive structural information by collision induced dissociation (CID)-MS/MS. Indeed, when the charge state of the selected molecular ion is low, neutral SO 3 losses most often predominate in comparison with glycosidic backbone cleavages [2]. This situation can be improved by combining MS/MS data resulting from different charge states.Very recently, Amster and coworkers published outstanding results showing how promising the electron detachment dissociation (EDD) of deprotonated sulfated oligosaccharides can be in providing informative fragment ions [3]. In particular, they documented the discrimination between the C5 epimeric glucuronic and iduronic acids based on specific fragment ions [4]. As in CID mode, they also observed that SO 3 loss can be dramatically reduced when EDD is performed on the charge states where the carboxylate group is ...

“…The preferential cleavage between the ␣-and carbonyl-carbon atoms of singly charged peptides having C-or N-terminal arginine yielded uniform and easily interpretable distributions of x-and a-type ions. We recently expanded the utility of photofragmentation to the characterization of native and derivatized linear oligosaccharides as well as permethylated acidic glycans [49,50]. Photodissociation yielded intense cross-ring fragmentation of Girard's T derivatized oligosaccharides and the product ions correspond to high-energy fragmentation pathways [49].…”

mentioning

confidence: 99%

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

Devakumar

Mechref

Kang

et al. 2008

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Characterization of structural isomers has become increasingly important and extremely challenging in glycobiology. This communication demonstrates the capability of ion-trap mass spectrometry in conjunction with 157 nm photofragmentation to identify different structural isomers of permethylated N-glycans derived from ovalbumin without chromatographic separation. The results are compared with collision-induced dissociation (CID) experiments. Photodissociation generates extensive cross-ring fragment ions as well as diagnostic glycosidic product ions that are not usually observed in CID MS/MS experiments. The detection of these product ions aids in characterizing indigenous glycan isomers. The ion trap facilitates MS n experiments on the diagnostic glycosidic fragments and cross-ring product ions generated through photofragmentation, thus allowing unambiguous assignment of all of the isomeric structures associated with the model glycoprotein used in this study. Photofragmentation is demonstrated to be a powerful technique for the structural characterization of glycans. , and protein regulations and interactions [6], is widely acknowledged [7]. To improve our understanding of these processes, it is important to explore glycan structure-function relationships. However, the detailed characterization of a glycan structure and its attributes remains a difficult task, given the microheterogeneity and diversity of these molecules. Importantly, the discrimination of numerous structural isomers differing in sequence, linkage, position, or branching features remains a challenging frontier of glycobiology.For years, the characterization of glycan structures has almost exclusively been accomplished by tandem mass spectrometry (MS/MS) [1,8,9] because of its high sensitivity and minimum sample requirements relative to nuclear magnetic resonance (NMR). Different combinations of ionization techniques, ion activation, and A glycan ion generally fragments in two ways: (1) glycosidic cleavages resulting from a bond rupture between two adjacent sugar residues and (2) cross-ring cleavages in which any two bonds on the same sugar unit are broken. Cross-ring fragment ions are commonly observed in high-energy collision-induced dissociation (CID) methods as demonstrated in the tandem TOF/TOF approach [34 -38]. A limitation of this technique, however, is its inability to perform multistage tandem mass spectrometry experiments. On the other hand, glycosidic cleavage ions are predominantly observed in low-energy activation methods and are mainly used to derive sequence and limited branching information. Most recently, demonstrated the use of low-energy activation to identify the structural isomers of glycans in complex mixtures with the help of sequential tandem mass spectrometry (MS n ). However, a disadvantage of CID is the decrease in both the degree and efficiency of dissociation with increasing mass and MS n events. Alternatively, other activation techniques have been used for Address reprint requests to Prof. James P.