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Abstract Signal Amplification By Reversible Exchange in SHield Enabled Alignment Transfer (SABRE‐SHEATH) is investigated to achieve rapid hyperpolarization of13C1spins of [1‐13C]pyruvate, using parahydrogen as the source of nuclear spin order. Pyruvate exchange with an iridium polarization transfer complex can be modulated via a sensitive interplay between temperature and co‐ligation of DMSO and H2O. Order‐unity13C (>50 %) polarization of catalyst‐bound [1‐13C]pyruvate is achieved in less than 30 s by restricting the chemical exchange of [1‐13C]pyruvate at lower temperatures. On the catalyst bound pyruvate, 39 % polarization is measured using a 1.4 T NMR spectrometer, and extrapolated to >50 % at the end of build‐up in situ. The highest measured polarization of a 30‐mM pyruvate sample, including free and bound pyruvate is 13 % when using 20 mM DMSO and 0.5 M water in CD3OD. Efficient13C polarization is also enabled by favorable relaxation dynamics in sub‐microtesla magnetic fields, as indicated by fast polarization buildup rates compared to theT1spin‐relaxation rates (e. g., ∼0.2 s−1versus ∼0.1 s−1, respectively, for a 6 mM catalyst‐[1‐13C]pyruvate sample). Finally, the catalyst‐bound hyperpolarized [1‐13C]pyruvate can be released rapidly by cycling the temperature and/or by optimizing the amount of water, paving the way to future biomedical applications of hyperpolarized [1‐13C]pyruvate produced via comparatively fast and simple SABRE‐SHEATH‐based approaches.
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1 H‐decoupling and Isotopic Labeling for the Measurement of the Longitudinal Relaxation Time of Hyperpolarized 13 C‐Methylenes in Choline Analogs
Abstract The T1of a hyperpolarized site in solution is a key parameter that determines the time‐window in which its NMR signals are observable. For13C sites adjacent to protons,1H‐decoupling has been shown to increase the hyperpolarized signal resolution and SNR. Additionally, polarization transfer to protons has shown utility in increasing the sensitivity of detection. However,1H‐decoupling could lead to a change in the decay rate of a hyperpolarized13C site. Here we tested this possible effect in a case where the protons are directly bound to an sp3hyperpolarized13C site (using [1,2‐13C2]choline) and1H‐decoupling was applied continuously throughout the hyperpolarized decay measurement. We found that1H‐decoupling did not lead to any significant changes in the13C polarization decay time but did result in the expected collapse of J‐coupling and produced sharper signals. This result suggested that1H‐decoupling did not affect the decay rate of hyperpolarized sp3 13C sites. The deuterium‐substitution approach (using [1,1,2,2‐D4,1‐13C]choline) showed a dramatic prolongation of T1. Upper bounds on the T1of all investigated sites were calculated.
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- Award ID(s):
- 1710046
- PAR ID:
- 10126653
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Israel Journal of Chemistry
- Volume:
- 59
- Issue:
- 11-12
- ISSN:
- 0021-2148
- Page Range / eLocation ID:
- p. 1014-1019
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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