Major glycan structures found in OA chondrocytes. Major N-glycan and O-glycan species, that is, oligomannosidic structures, non-, mono- and disialylated N-glycans, β4GalNAc-containing N-glycans as well as mucin-type core 2 O-glycans, were identified and quantified independently in chondrocytes from three patients by LC–ESI-MS. Results shown were obtained from chondrocytes of one patient (n = 1) and are representative of three independent experiments with similar results. Glycans are referred to according to the ‘proglycan’ nomenclature (http://www.proglycan.com). The oligosaccharides shown here were selected for quantification with LC-ESI-MS, because they are among the most abundant glycan structures in human chondrocytes and are essentially absent in the glycome of the fetal calf serum-containing cell culture medium, which can otherwise contaminate the chondrocyte glycome to some extent. As a measure of quantity the mean peak area values obtained by LC–ESI-MS are given for each structure. For each peak area, the standard deviation resulting from two technical replicates was below 15%. LC–ESI-MS, liquid chromatography-electrospray ionization-mass spectrometry; OA, osteoarthritis.