25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

Dynamic nuclear polarization of 13C in the liquid state over a 10 Tesla field range

28 Aug 2019, 14:05
10m
Max Kade Auditorium (Henry Ford Building)

Max Kade Auditorium

Henry Ford Building

Prize lecture Hyperpolarization techniques Prize Lectures

Speaker

Dr Tomas Orlando (RG ESR Spectroscopy, Max Planck Institute for Biophysical Chemistry)

Description

DNP in liquids is driven by electron-nuclear cross-relaxation, known as Overhauser effect (O-DNP). When relaxation is dominated by scalar hyperfine interaction, the enhancements can reach three orders of magnitudes, as recently reported for $^{13}$C-DNP at 3.4 T [1].
Hereby we present a systematic study performed at different magnetic fields on model systems doped with nitroxide radical (TEMPONE) as polarizing agent [2]. $^{13}$C signal enhancements on organic small molecules in liquids at room temperature were observed as high as 800 at 1.2 Tesla and 600 at 9.4 Tesla. An accurate determination of Overhauser parameters allowed us to disclose the primary role of the scalar hyperfine interaction to the $^{13}$C nuclei as mediated by molecular collisions in the sub-picoseconds timescale.
Experimental measurements performed at 1.2 T, 9.4 T, and 14 Tesla allowed us to complete the characterization of the polarization transfer efficiency over a broad frequency range and described it by the subtle combination of dipolar and scalar relaxation.
Furthermore, we recognized that a proper choice of polarizing agent/target system is essential to optimize the efficiency of scalar O-DNP. Indeed, fullerene-nitroxide derivatives are superior to TEMPONE radical as polarizing agent at low fields, while halogens atoms (Cl, Br) bound to the target C nucleus seems to favor the scalar interaction.
The observation of sizable DNP of $^{13}$CH$_2$ and $^{13}$CH$_3$ groups in organic molecules at 9.4 T preserving NMR resolution opens perspectives for a broader application of this method as a tool to address $^{13}$C-NMR sensitivity issues at high fields.

[1] Liu G., Levien M., Karschin N., Parigi G., Luchinat C., and Bennati M. Nat. Chem. 9, 676-680 (2017)
[2] Orlando T., Dervisoglu R., Levien M., Tkach I., Prisner T.F., Andreas L.B., Denysenkov V., Bennati M. Angew. Chem. Int. Ed. 58, 1402-1406 (2019)

Primary authors

Dr Tomas Orlando (RG ESR Spectroscopy, Max Planck Institute for Biophysical Chemistry) Dr Riza Dervisoglu (Department of NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry) Mr Marcel Levien (RG ESR Spectroscopy, Max Planck Institute for Biophysical Chemistry) Dr Igor Tkach (RG ESR Spectroscopy, Max Planck Institute for Biophysical Chemistry) Prof. Thomas F. Prisner (Institute of Physical and Theoretical Chemistry and Center for Biomolecular Resonance, Goethe University Frankfurt) Dr Loren Andreas (Department of NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry) Dr Vasyl Denysenkov (Institute of Physical and Theoretical Chemistry and Center for Biomolecular Resonance, Goethe University Frankfurt) Prof. Marina Bennati (RG ESR Spectroscopy, Max Planck Institute for Biophysical Chemistry)

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