Frequency-swept dynamic nuclear polarization
Name
nihms-2028359.pdf
Description
Accepted version
Size
889.04 KB
Format
Adobe PDF
Checksum (MD5)
7b5b6eacaf2f5b356d651f0e7610a9ba
Author(s)
Mardini, Michael
Palani, Ravi Shankar
Ahmad, Iram M
Mandal, Sucharita
Jawla, Sudheer K
Bryerton, Eric
Temkin, Richard J
Sigurdsson, Snorri Th
Griffin, Robert G
Date Issued
August 2023
Journal
Journal of Magnetic Resonance
Publisher
Elsevier BV
Version
Author's final manuscript
Abstract
Dynamic nuclear polarization (DNP) improves the sensitivity of NMR spectroscopy by the transfer of electron polarization to nuclei via irradiation of electron-nuclear transitions with microwaves at the appropriate frequency. For fields > 5 T and using g ∼ 2 electrons as polarizing agents, this requires the availability of microwave sources operating at >140 GHz. Therefore, microwave sources for DNP have generally been continuous-wave (CW) gyrotrons, and more recently solid state, oscillators operating at a fixed frequency and power. This constraint has limited the DNP mechanisms which can be exploited, and stymied the development of new time domain mechanisms. We report here the incorporation of a microwave source enabling facile modulation of frequency, amplitude, and phase at 9 T (250 GHz microwave frequency), and we have used the source for magic-angle spinning (MAS) NMR experiments. The experiments include investigations of CW DNP mechanisms, the advantage of frequency-chirped irradiation, and a demonstration of an Overhauser enhancement of ∼25 with a recently reported water-soluble BDPA radical, highlighting the potential for affordable and compact microwave sources to achieve significant enhancement in aqueous samples, including biological macromolecules. With the development of suitable microwave amplifiers, it should permit exploration of multiple new avenues involving time domain experiments.
Terms of Use
Creative Commons Attribution-NonCommercial-NoDerivatives
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1016/j.jmr.2023.107511
