HFX LT-MAS DNP-NMR probe head and 19F-upgrade

• Subject Area: Chemical Solid State and Surface Research
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565971724

With the increasing size of biomolecules under investigation by solid-state NMR under magic-angle spinning (MAS) for structure and function elucidation, the need for spectral sensitivity and selectivity becomes ever clearer. While the sensitivity problem is being successfully addressed by several methods including dynamic nuclear polarization (DNP), the selectivity problem remains more of an open question. In this regard, DNP-enhanced 19F NMR offers truly outstanding opportunities in terms of both sensitivity and selectivity: fluorine is not naturally occurring in biomolecules and carries an isotopically pure, high-sensitivity spin-1/2 nucleus (19F). This allows for introduction of specific nuclear spin labels into large biomolecules and biomolecular complexes, enabling spatially selective spectroscopy of biomolecular sites of interest by 19F NMR techniques. Furthermore, DNP also introduces the possibility of utilizing different mechanisms and methods, such as indirect or direct DNP, as well as methods based on molecular motions such as specific cross-relaxation enhancement by active motions under DNP (SCREAM-DNP) for tailoring pathways of hyperpolarization and thus controlling spectral selectivity. Developing and applying these methods requires a dedicated low-temperature MAS (LTMAS) DNP NMR probe capable of simultaneous excitation of 1H and 19F for cross-polarization and high-power decoupling in addition to an NMR spectrometer fitted with at least two high-frequency channels. Such hardware is rarely available in laboratories worldwide, therefore, most existing studies using DNP-enhanced 19F NMR are currently performed using regular probes with the 1H channel being retuned to 19F frequency, not allowing for cross-polarization or decoupling of 1H in the sample and thus limiting the scope of currently applicable experiments. Therefore, we request a dedicated 1.9 mm triple-channel HFX LTMAS DNP probe suitable for operations with our existing 9.4 T / 400 MHz / 263 GHz DNP NMR spectrometer, including the required instrumentation for adding a second high-frequency channel to the latter (transmitter board, high-power amplifier, preamplifier, filters, and cables). This probe allows for 1H-19F cross-polarization, as well as simultaneous 1H and 19F decoupling and opens up all possibilities for development, characterization, and application of the above-mentioned methods. With this instrument we will investigate the differences between 1H and 19F in DNP build-up and propagation in indirect and direct DNP and develop method for optimization of sensitivity and selectivity of each method. Furthermore, we will apply these advantages to challenging problems with significant societal impact such as the investigation of the toxicology of perfluoroalkyl substances on zebrafish models and the development and characterization of drug-carrier systems as well as filter materials for removal of amyloid-beta from blood plasma.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: HFX LT-MAS DNP-NMR-Probenkopf und 19F-Upgrade
• Instrumentation Group: 1741 Festkörper-NMR-Spektrometer
• Applicant Institution: Universität Rostock
• Leader: Professor Dr.-Ing. Björn Corzilius