Molecular Insights into Biomolecular Structure and Dynamics by 14N NMR

The structural and dynamic analysis of proteins by NMR in the solid-state has typically required extensive isotope labelling. Here we report our progress using the naturally occurring isotopes 1H and 14N to probe the structure and dynamics of biomolecules. Employing indirect-detection methods, we have previously demonstrated the feasibility of characterising the quadrupolar interaction present at the naturally occurring 14N sites within proteins using 13C as a ‘spy’ nucleus (Jarvis, 2013). These methods demonstrated that in well folded proteins, limited dynamic averaging of the quadrupolar interaction occurred and the magnitude of the quadrupolar interaction reflected the nature of the hydrogen bonding experienced by the nitrogen, with differences of up to 200 kHz measured between amides in alpha helices and beta sheets - allowing a detailed analysis of the electronic environment along the protein backbone. We have extended this methodology to exploit protons as a spy nucleus, where significant enhancements in sensitivity are realised. These advances have opened up the possibility of conducting a molecular analysis of unlabelled biomolecules such as ex-vivo or environmental samples. Currently, we are applying these methods to amyloid fibres, to provide insights into their backbone conformation and polymorphism.Jarvis, J.A., Haies, I.M., et al., An efficient NMR method for the characterisation of 14N sites through indirect 13C detection. Phys Chem Chem Phys, 2013. 15(20): p. 7613-20.