Identification of isomeric N-glycan structures by mass spectrometry with 157 nm laser-induced photofragmentation
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- Devakumar, A., Mechref, Y., Kang, P. et al. J Am Soc Mass Spectrom (2008) 19: 1027. doi:10.1016/j.jasms.2008.03.005
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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 MSn 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.