High-field Dynamic Nuclear Polarization Magic Angle Spinning NMR for Chemistry, Physics, Materials, Pharmaceuticals and Biomolecular Science

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Solid-state nuclear magnetic resonance (NMR) is a spectroscopic technique which is used to study the molecular structure and dynamics of systems from the advanced materials used for hydrogen storage, drug delivery and catalysis to biological molecules, such as proteins and RNA. However, compared to other approaches, solid-state NMR suffers from a lack of sensitivity and long acquisition times for signal accumulation or large sample volumes are required. The amount of signal acquired in a NMR experiment depends on the nuclear spin polarization which arises in the presence of a magnetic field, and since the magnetic moments of nuclei are relatively weak, a superconducting magnet is required. However, even with the strongest superconducting magnets available today, NMR studies of dilute species, such as molecules adsorbed on surfaces, proteins in whole cells or isotopes with low natural abundance, are impossible.However, the electronic magnetic moment is about three orders of magnitude stronger than that for the hydrogen nucleus and consequently unpaired electrons in radicals carry a much larger spin polarization. Hence, the NMR signal can be enhanced by so-called dynamic nuclear polarization (DNP) which involves the transfer of the large electronic polarization from radicals implanted in the sample onto neighbouring nuclei via their mutual dipolar coupling. The DNP process requires the saturation of particular frequencies in the electron spin resonance spectrum using a strong microwave source. The principles of DNP have been known since the early days of NMR, but the technique was limited to magnetic fields much smaller than those used in modern NMR spectrometers with severe implications for the resolution of chemical sites. However, the development of gyrotrons as high-power microwave sources has made robust DNP instrumentation operating at high frequencies possible. Signal enhancements of up to 300-fold can now be achieved, corresponding to a reduction of a factor of 100000 in the required measuring time. The recent commercialization of DNP hardware makes it possible to focus on applications in a wide range of scientific disciplines rather than having to worry about the complex instrumental requirements.This proposal aims to provide access to DNP solid-state NMR for a broad section of the UK science community by installing a DNP Facility at the University of Nottingham based on a commercial instrument.