Stable isotopic labeling-based quantitative targeted glycomics (i-QTaG)

Biotechnol Prog. 2015 May-Jun;31(3):840-8. doi: 10.1002/btpr.2078. Epub 2015 Apr 15.


Mass spectrometry (MS) analysis combined with stable isotopic labeling is a promising method for the relative quantification of aberrant glycosylation in diseases and disorders. We developed a stable isotopic labeling-based quantitative targeted glycomics (i-QTaG) technique for the comparative and quantitative analysis of total N-glycans using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). We established the analytical procedure with the chemical derivatizations (i.e., sialic acid neutralization and stable isotopic labeling) of N-glycans using a model glycoprotein (bovine fetuin). Moreover, the i-QTaG using MALDI-TOF MS was evaluated with various molar ratios (1:1, 1:2, 1:5) of (13) C6 /(12) C6 -2-aminobenzoic acid-labeled glycans from normal human serum. Finally, this method was applied to direct comparison of the total N-glycan profiles between normal human sera (n = 8) and prostate cancer patient sera (n = 17). The intensities of the N-glycan peaks from i-QTaG method showed a good linearity (R(2) > 0.99) with the amount of the bovine fetuin glycoproteins. The ratios of relative intensity between the isotopically 2-AA labeled N-glycans were close to the theoretical molar ratios (1:1, 1:2, 1:5). We also demonstrated that the up-regulation of the Lewis antigen (~82%) in sera from prostate cancer patients. In this proof-of-concept study, we demonstrated that the i-QTaG method, which enables to achieve a reliable comparative quantitation of total N-glycans via MALDI-TOF MS analysis, has the potential to diagnose and monitor alterations in glycosylation associated with disease states or biotherapeutics.

Keywords: MALDI-MS; N-glycan; comparative quantitation; sialic acid neutralization; stable isotopic labeling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Case-Control Studies
  • Cattle
  • Evaluation Studies as Topic
  • Fetuins / chemistry
  • Glycomics / methods*
  • Glycosylation
  • Humans
  • Isotope Labeling*
  • Male
  • N-Acetylneuraminic Acid
  • Polysaccharides / blood*
  • Prostatic Neoplasms / blood
  • Reproducibility of Results
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Up-Regulation
  • ortho-Aminobenzoates / chemistry


  • Fetuins
  • Polysaccharides
  • ortho-Aminobenzoates
  • anthranilic acid
  • N-Acetylneuraminic Acid