Our research interests are principally concerned with determining molecular structures and dynamics in solid, biologically-relevant materials, primarily using nuclear magnetic resonance (NMR) spectroscopy. NMR is an excellent tool for determining molecular structure in chemical systems not amenable to conventional diffraction techniques, such as composite materials, heterogeneous systems and microcrystalline materials. Our particular area of interest is solid structural proteins, for instance keratin (hair, fingernails, hoof, etc) and collagen (tendon, bone, blood vessels etc.) and biominerals/ biomaterials such as bone. Bone is a composite material consisting of an organic matrix (primarily collagen) with inorganic crystals (hydroxyapatite) deposited in it. We are using solid-state NMR to study the nature of the interface between these two components, the interfacial region being critical to the structural properties of this important biological material. Our results have shown for the first time how the organic matrix is bound to the inorganic phase (see figure).
The model of protein carboxylate - hydroxyapatite surface binding proposed from our recent work. The grey plane represents the "surface" of the hydroxyapatite crystal. Surface phosphate anions are thought to be protonated as shown. Protein binds to the calcium ions in the surface via carboxylate residues on glutamate of γ-carboxyglutamate residues.
NMR is also an excellent method for the study of molecular dynamics in solids. Studying molecular motion enables us to probe intermolecular potentials in solids. In turn, understanding the intermolecular potential is a prerequisite to understanding the physical and material properties of solids, such as structure, ability to withstand and dissipate stresses, phase transitions, etc, in addition to chemical reactivity. Structural proteins are of particular interest currently. Studies of molecular dynamics in these systems will eventually help us in understanding their very important material properties in nature.
To perform the types of solid-state NMR investigation outlined above, we are constantly in need of new and better NMR experiments to study molecular structure, in particular. Thus, a further proportion of our work is in developing new solid-state NMR methodologies.
The organic-mineral interface in teeth is like that in bone and dominated by polysaccharides: universal mediators of calcium phosphate biomineralization in vertebrates?, D.G. Reid, M.J. Duer, R.C. Murray, E. R. Wise, Chem. Mat. 20 (2008) 3549 - 3550
The role of glycosaminoglycans in mineral formation in bone: a solid-state NMR study of chondroitin sulfate: calcium phosphate complexes, S.M. Best, M.J. Duer, D.G. Reid, E.R. Wise, D. Zho. Magn. Reson. Chem. 45 (2007) 1-7
The mineral-organic interface in bone is lined by polysaccharide, E.R. Wise, S. Maltsev, M. Elisabeth Davies, M.J. Duer, C. Jaeger, N. Loveridge, R.C. Murray, and D.G. Reid. Chem. Mat. 19 (2007) 5055-5057
An Introduction to Solid-State NMR, M.J. Duer, Blackwell Science Ltd (Oxford) , (2004)
A solid-state NMR study of the structure and mobility of α-keratin, M.J. Duer, N. McDougal and R.C. Murray, Phys. Chem. Chem. Phys. 5 (2003) 2894-2899