Differentiation of isomeric N-glycan structures by normal-phase liquid chromatography-MALDI-TOF/TOF tandem mass spectrometry

Anal Chem. 2006 Dec 15;78(24):8491-8. doi: 10.1021/ac0614137.

Abstract

The detailed characterization of protein N-glycosylation is very demanding given the many different glycoforms and structural isomers that can exist on glycoproteins. Here we report a fast and sensitive method for the extensive structure elucidation of reducing-end labeled N-glycan mixtures using a combination of capillary normal-phase HPLC coupled off-line to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and TOF/TOF-MS/MS. Using this method, isobaric N-glycans released from honey bee phospholipase A2 and Arabidopsis thaliana glycoproteins were separated by normal-phase chromatography and subsequently identified by key fragment ions in the MALDI-TOF/TOF tandem mass spectra. In addition, linkage and branching information were provided by abundant cross-ring and "elimination" fragment ions in the MALDI-CID spectra that gave extensive structural information. Furthermore, the fragmentation characteristics of N-glycans reductively aminated with 2-aminobenzoic acid and 2-aminobenzamide were compared. The identification of N-glycans containing 3-linked core fucose was facilitated by distinctive ions present only in the MALDI-CID spectra of 2-aminobenzoic acid-labeled oligosaccharides. To our knowledge, this is the first MS/MS-based technique that allows confident identification of N-glycans containing 3-linked core fucose, which is a major allergenic determinant on insect and plant glycoproteins.

MeSH terms

  • Amination
  • Animals
  • Arabidopsis / chemistry*
  • Bees / chemistry*
  • Carbohydrate Sequence
  • Chromatography, High Pressure Liquid / methods
  • Glycoproteins / analysis
  • Glycoproteins / chemistry
  • Isomerism
  • Molecular Sequence Data
  • Phospholipases A / chemistry
  • Phospholipases A / metabolism
  • Phospholipases A2
  • Polysaccharides / analysis
  • Polysaccharides / chemistry
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods*
  • Tandem Mass Spectrometry / methods*
  • ortho-Aminobenzoates / chemistry

Substances

  • Glycoproteins
  • Polysaccharides
  • ortho-Aminobenzoates
  • anthranilic acid
  • Phospholipases A
  • Phospholipases A2
  • anthranilamide