A THz Resonator for Solid-State DNP-NMR Spectroscopy

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DESCRIPTION (provided by applicant): The proposed research focuses on the development of a terahertz (THz) resonator for Dynamic Nuclear Polarization (DNP) enhanced solid-state NMR spectroscopy (ssNMR). With DNP, the inherently small signal intensities in an NMR experiment can be enhanced by several orders of magnitude. This significantly increased overall sensitivity will be of great value for many applications of ssNMR spectroscopy as well as the structural characterization of bio-macromolecules. In the last decade, DNP has proven to be a robust method to increase high-field, in solid-state NMR (SSNMR) signal intensities laboratories around the world. However, currently the sample is directly illuminated by the THz radiation, a very inefficient process that requires high-power THz sources to efficiently drive the DNP process. The common assumption is, that the transverse size of a fundamental mode resonator (radius ~0.75 mm for 198 GHz, corresponding to 300 MHz 1H) is too small to accommodate sample sizes that are typically used in ssNMR spectroscopy such as Magic Angle Spinning (MAS) rotors. The innovative idea proposed in this Phase I SBIR proposal focuses on the development of a novel, resonance structure which will increase the THz induced B1e field strength and minimize the amount of required THz power while not interfering with the RF structure of the NMR probe and thus maintaining lineshape integrity of the probe. This is of specific importance for high-field DNP spectroscopy (> 600 MHz, 1H) where reducing the amount of necessary terahertz power will allow the use of compact and cost-effective (~$40,000 - 50,000) solid state sources instead of large and expensive (~1$M) gyrotron systems. In addition the proposed research could eventually lead to THz resonators that are required for future pulsed DNP experiments. The successful development of this probe will enable the rapid proliferation of DNP-enhanced ssNMR spectroscopy for structural biology, pharmaceutical research and analytical chemistry, which are of interest in many projects funded by the U.S. National Institutes of Health.