Article

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 

Abstract

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.