Category Archives: 19F

19F Magic Angle Spinning Dynamic Nuclear Polarization Enhanced NMR Spectroscopy #DNPNMR

Viger-Gravel, Jasmine, Claudia E. Avalos, Dominik J. Kubicki, David Gajan, Moreno Lelli, Olivier Ouari, Anne Lesage, and Lyndon Emsley. “19F Magic Angle Spinning Dynamic Nuclear Polarization Enhanced NMR Spectroscopy.” Angewandte Chemie International Edition 58, no. 22 (May 27, 2019): 7249–53.

The introduction of high frequency, high power microwave sources, tailored biradicals, and low-temperature magic- 30 angle spinning probes has led to a rapid development of hyperpolarization strategies for solids and frozen solutions, leading to large gains in NMR sensitivity. Here, we introduce a protocol for efficient hyperpolarization of 19F nuclei in MAS DNP enhanced NMR. We identify trifluoroethanol-d3 as a versatile glassy matrix and show that 12 mM AMUPol (with microcrystalline KBr) provides direct 19F DNP enhancements of over 100 at 9.4 T. We apply this protocol to 10 obtain DNP-enhanced 19F and 19F-13C cross-polarization (CP) spectra for an active pharmaceutical ingredient and a fluorinated mesostructured hybrid material, using incipient wetness 40 impregnation with enhancements of ~25 and ~10 in the bulk solid, respectively. This strategy is a general and straightforward method for obtaining enhanced 19F MAS spectra from fluorinated materials.

19F Dynamic Nuclear Polarization at Fast Magic Angle Spinning for NMR of HIV-1 Capsid Protein Assemblies #DNPNMR

This is great work showing off the capabilities of DNP to study 19F in biological samples.

Lu, Manman, Mingzhang Wang, Ivan V. Sergeyev, Caitlin M Quinn, Jochem Struppe, Melanie Rosay, Werner Maas, Angela M. Gronenborn, and Tatyana Polenova. “19F Dynamic Nuclear Polarization at Fast Magic Angle Spinning for NMR of HIV-1 Capsid Protein Assemblies.” Journal of the American Chemical Society, March 15, 2019.

We report remarkably high, up to 100-fold, signal enhancements in 19F dynamic nuclear polarization (DNP) magic angle spinning (MAS) spectra at 14.1 T on HIV-1 CA capsid protein assemblies. These enhancements correspond to absolute sensitivity ratios of 12-29 and are of similar magnitude as seen for 1H signals in the same samples. At MAS frequencies above 20 kHz, it was possible to record 2D 19F-13C HETCOR spectra, which contain long-range intra- and intermolecular correlations. Such correlations provide unique distance restraints, inaccessible in conventional experiments without DNP for protein structure determination. Furthermore, systematic quantification of the DNP enhancements as a function of biradical concentration, MAS frequency, temperature, and microwave power is reported. Our work establishes the power of DNP-enhanced 19F MAS NMR spectroscopy for structural characterization of HIV-1 CA assemblies and this approach is anticipated to be applicable to a wide range of large biomolecular systems.

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