Structural Characterization of Bone by Solid-State NMR Spectroscopy

Thanks to NIH funding support

"Dehydration-Controlled Structural Changes in Intact Cortical Bone by Solid-State NMR Spectroscopy"

We have been investigating the dehydration-induced conformational changes in intact bones using ¹³C and ¹H magic-angle-spinning (MAS) NMR experiments:

Carbon-13 Ramp-CP MAS ssNMR spectra of intact fresh and dehydrated 60 mg bovine cortical bone samples. Both spectra were collected on a Varian VNMRS 600 MHz NMR spectrometer using a 4 mm double-resonance MAS probe with a 2 ms ramp cross-polarization under 10 kHz spinning speed. The bone samples were shaped to a 2.5 × 2.5 × 12 mm size and inserted into 4 mm zirconia MAS rotors.

"Natural-Abundance ⁴³Ca Solid-State NMR Spectroscopy of Bone"

We have been analyzing the calcium coordination environment of bovine cortical bone and model compounds for bone mineral, including hydroxyapatite and carbonated apatite, using ⁴³Ca 1D MAS and 2D 3Q-MAS NMR experiments:

Two-dimensional 3Q-MAS ⁴³Ca ssNMR spectrum that correlates the ⁴³Ca chemical shift and a triple-quantum frequency of ⁴³Ca-enriched carbonated apatite powder sample containing osteocalcin protein at room temperature. The spectrum was collected on a Bruker 833 MHz NMR spectrometer using a single-channel 4 mm MAS probe tuned to 55.8 MHz, with a 10 kHz spinning speed.

"Insights Into the Dehydration of Cartilage via Solid-State NMR Spectroscopy"

We have been investigating the structure and dynamics of polymeric molecules of articular cartilage using time-resolved solid-state NMR spectroscopy during dehydration. Our results reveal that dehydration reduces the mobility of collagen amino acid residues and carbon sugar ring structures in glycosaminoglycans but has no effect on the trans-Xaa-Pro conformation. Equally interestingly, our results demonstrate that the dehydration effects are reversible, and the molecular structure and mobility are restored upon rehydration.