MRI: Development of Instrumentation for Dynamic Nuclear Polarization of Organic Solutions

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With this award from the Major Research Instrumentation Program, Professor Stephen Hill from Florida State University (FSU) and the National High Magnetic Field Laboratory (NHMFL) and colleagues William Brey and Johan van Tol will develop a custom spectrometer equipped with a magnet and probes capable of supporting both high-resolution nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) at relatively high fields and frequencies. The main idea is to combine these methodologies, resulting in a high-field dynamic nuclear polarization (DNP) instrument for organic solutions that would allow the study of samples that are mass limited and thus can only be prepared in very low concentrations. The target is to operate at 14.1 T, requiring nuclear and electron irradiation at 600 MHz and 395 GHz, respectively. The design is based on rapid shuttling inside the NMR magnet between the homogeneity sweet spot, which will be used for the NMR experiments, and a location just above, where the DNP will be performed by microwave irradiation. The new instrument will lead to an enhancement in sensitivity of the typical organic NMR experiment (including essentially any NMR experiment implemented today on molecules dissolved in organic solvent) by over two orders of magnitude. A 50-fold enhancement in sensitivity is expected with successful DNP implementation, with further gains coming from adapting existing NHMFL-based orthogonal technologies utilizing cryogenic high temperature superconducting NMR probe platforms. Such enhancements will open wide new fields of applications in many of areas of interest to NMR spectroscopists. Examples are organic structure determinations, synthesis and screening of pharmaceuticals, elucidation of natural product structures, and metabolomics analyses.The proposed instrument will combine three techniques: nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and dynamic nuclear polarization (DNP). NMR spectroscopy is one of the most powerful tools available to chemists for the elucidation of the structure of molecules. It is used to identify unknown substances, to characterize specific arrangements of atoms within molecules, and to study the dynamics of interactions between molecules in solution. Access to state-of-the-art NMR spectrometers is essential to chemists who are carrying out frontier research. Similarly, an EPR spectrometer yields detailed information on the geometric and electronic structure of molecular and solid state materials. It may also be used to obtain information about the lifetimes of short-lived, highly reactive species involved in important chemical and biochemical processes. DNP utilizes EPR in order to overcome one of NMR's main drawbacks - its inherent low sensitivity. By irradiating stable electron radicals that have been co-mixed with molecular targets of interest with high-power microwaves tuned to the appropriate EPR frequency (395 GHz in this case), polarization can be transferred to the target nuclei via the electron spins. The increased nuclear polarization results in increased sensitivity in NMR experiments and thus improves the chances of using samples that can only be prepared in very low concentrations, e.g., from rare natural products or bioproducts. This research will have a major impact in improving NMR screening capabilities and will catalyze pharmaceutical development, while also training the next generation of instrumentalists by combining the expertise of chemists, physicists and biochemists.