Journal of the American Society for Mass Spectrometry

, Volume 19, Issue 7, pp 1027-1040

First online:

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

  • Arugadoss DevakumarAffiliated withDepartment of Chemistry, Indiana University
  • , Yehia MechrefAffiliated withDepartment of Chemistry, Indiana University
  • , Pilsoo KangAffiliated withDepartment of Chemistry, Indiana University
  • , Milos V. NovotnyAffiliated withDepartment of Chemistry, Indiana University
  • , James P. ReillyAffiliated withDepartment of Chemistry, Indiana University Email author 


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.