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Surface-Only Spectroscopy for Diffusion-Limited Systems Using Ultra-Low Temperature DNP MAS NMR at 16.4 T

preprint
submitted on 22.05.2020 and posted on 22.05.2020 by Yoh Matsuki, Tomoaki Sugishita, Toshimichi Fujiwara
Conventional dynamic-nuclear-polarization (DNP) technique at T ~100 K can enhance sensitivity of magic-angle spinning (MAS) NMR over 100-fold for standard samples containing urea/proline at high-field conditions, B0= 9.4–16.4 T. In the scene of real applications, however, the achievable enhancement is often much lower than for urea/proline due to faster 1H relaxation (T1H) promoted by molecular-segmental fluctuations and methyl-group rotations active even at low temperatures, hindering an efficient polarization diffusion within the system. Here, we show at 16.4 T that ultra-low temperature (T≪100 K) provides a general way to improve the DNP efficiency for such diffusion-limited systems as we demonstrate on microcrystalline sample of a tripeptide N-f-MLF-OH. In a further step, the hyperpolarization localized at the crystal surface enabled “surface-only” spectroscopy eliminating background signals from the crystal core. The surface-only data, rather than the currently popular surface-enhanced data, should prove to be useful in many applications in biological and material sciences.

Funding

This work was supported by JST SENTAN (H271030 and JPMJSN15A1), the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan (480790) (Y.M., T.F.).

History

Email Address of Submitting Author

yoh@protein.osaka-u.ac.jp

Institution

Institute for Protein Researc, Osaka University

Country

Japan

ORCID For Submitting Author

0000-0001-5339-6123

Declaration of Conflict of Interest

No conflict of interest.

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