13C Dynamic Nuclear Polarization using SA-BDPA at 6.7 T and 1.1 K: Coexistence of Pure Thermal Mixing and Well-Resolved Solid Effect

Alice Radaelli, Hikari A.I. Yoshihara, Hiroshi Nonaka, Shinsuke Sando, Jan Henrik Ardenkjær-Larsen, Rolf Gruetter, Andrea Capozzi*

*Corresponding author for this work

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Abstract

SA-BDPA is a water-soluble, narrow-line width radical previously used for dynamic nuclear polarization (DNP) signal enhancement in solid-state magic angle spinning NMR spectroscopy. Here, we report the first study using SA-BDPA under dissolution DNP conditions (6.7 T and 1.15 K). Longitudinal-detected (LOD)-electron spin resonance (ESR) and 13C DNP measurements were performed on samples containing 8.4 M [13C]urea dissolved in 50:50 water:glycerol (v/v) doped with either 60 or 120 mM SA-BDPA. Two distinct DNP mechanisms, both "pure"thermal mixing and a well-resolved solid effect could clearly be identified. The radical's ESR line width (30-40 MHz), broadened predominantly by dipolar coupling, excluded any contribution from the cross effect. Microwave frequency modulation increased the enhancement by DNP at the lower radical concentration but not at the higher radical concentration. These results are compared to data acquired with trityl radical AH111501, highlighting the unusual 13C DNP properties of SA-BDPA.
Original languageEnglish
JournalJournal of Physical Chemistry Letters
Volume11
Issue number16
Pages (from-to)6873-6879
ISSN1948-7185
DOIs
Publication statusPublished - 2020

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