A comparative study of glycoprotein concentration, glycoform profile and glycosylation site occupancy using isotope labeling and electrospray linear ion trap mass spectrometry

► Concentration, site occupancy and glycoform variation can be differentiated. ► Glycopeptides and peptides were stable isotope labeled and analyzed by ESI-MS. ► Nonglycosylated peptide provided glycoprotein concentration variation. ► Glycoform variation was obtained by comparing d0 and d4 labeled glycopeptides. ► The variation of glycosylation site occupancy could be calculated.