After finding an NMR and EPR signal for the pigment, we considered the effects of pigmentation on collagen structure. We inspected the spectra and found reproducible changes in the glycine Cα signals, which can be considered as monitors of collagen structural integrity. In NMR spectra of tissues with a high proportion of collagen, such as cartilage, this signal is one of the most intense due to the fact that glycines occur every third residue along each collagen chain. These signals combine into a C peak agglomerate centered at 42.7 ppm, well separated from Cα signals of other amino acids. In Fig. , we expand this particular spectral region from the HETCOR spectra acquired at different contact times on the various cartilage samples. At short contact times (top row), the glycine Cα signal at 42.7 ppm mainly correlates to an agglomerate of 1 H signals centered at 3.3 ppm, which correspond to the directly bonded glycine Hαs (1.1 Å). As the contact time is increased, a second correlation emerges, centered at 9.6 ppm ( 1 H) in the spectra of the non-pigmented AKU cartilage (green, middle column) and the OA cartilage (purple, right column). This signal can be attributed to correlations between glycine Cα and the respective HN (2.1 Å). This proton occurs at a comparably high chemical shift value of 9.6 ppm due to the interchain hydrogen bonding that is a defining feature of all collagen triple helices.