Fig. 2.

(A) A 2D ¹³C-¹³C correlation NMR spectrum (proton-driven spin-diffusion) of in vitro ECM from foetal sheep osteoblasts in which U-¹³C-Pro, Gly were used in the cell culture media, resulting in ECM proteins in which Gly, Pro and Hyp are extensively ¹³C-labelled. Correlation signals from these (primarily collagen) residues thus appear in this 2D correlation spectrum. Intraresidue signals are indicated in red rectangles and inter-residue correlations in blue rectangles. The inset (grey rectangle) is an expansion of the Pro C$\beta$ signals, showing they can be resolved into those from Pro in GPO and more general GPY triplets. The 1D ¹³C MAS NMR spectrum of the same sample is shown at the top. (B) 2D ¹³C-¹³C correlation NMR spectrum (proton-driven spin-diffusion) of in vitro calcifying (bovine) vascular smooth muscle cell ECM showing assignments of some of the correlation signals from poly(ADP ribose) (inset: structure of one monomer unit of poly(ADP ribose) showing the ¹³C site labelling scheme). The 1D ¹³C projection of the spectrum is shown above the 2D spectrum. The poly(ADP ribose) signals are not resolved from other glycan species in this 1D spectrum, although they are well-resolved in the 2D spectrum, showing the power of 2D NMR correlation spectroscopy.