Fig. 6
Post-translational modifications of collagen in OA subchondral bone. a Proper assembly of procollagens into the tropocollagen triple helix requires post-translational modifications such as prolyl hydroxylation. b An unmodified Col1A1 peptide (I954AGQRGVVGLP964, m/z 1 066.64) was nearly undetectable in OA subchondral bone, whereas the hydroxyproline-modified form (I954AGQRGVVGLP(ox)964, m/z 1 082.64) showed strong trabecular localization. c A Col1A1 peptide with three hydroxyproline residues (G656KP(ox)GEQGVP(ox)GDLGAP(ox)670, m/z 1 426.68) displayed high signal, while partially modified forms with 2, 1, or 0 HYP showed progressively weaker intensity and lower spatial definition. d Quantification across replicates (n = 4) from medial (grey) and lateral (white) OA tibial plateaus confirmed significant differences in hydroxyproline-modified peptide abundance (*P < 0.05, paired t-test)
