Probing Spatial Proximities Between Protons of Collagen Protein in Native Bone Using 2D 1H Multiple Quantum Experiments Under Fast MAS NMR

In solid-state nuclear magnetic resonance (ssNMR) spectroscopy, fast magic angle spinning (MAS) is a potent technique that efficiently reduces line broadening and makes it possible to probe structural details of biological systems in high resolution. However, its utilization in studying complex heterogeneous biomaterials such as bone in their native state has been limited. The present study has demonstrated the feasibility of acquiring two-dimensional (2D) ¹H-¹H correlation spectra for native bone using multiple-quantum/single-quantum correlation experiments (MQ/SQ) at fast MAS (70 kHz). This method uncovered distinct ¹H–¹H dipolar coupling networks involving long-chain charged residues of collagen protein, highlighting their role in maintaining the stability of the collagen triple helix. Our study opens up new avenues for ¹H-detected multi-quantum-based experiments at fast MAS on native collagen-containing biological systems to explore their complex heterogeneous structural details more efficiently.