The T1 of a hyperpolarized site in solution is a key parameter that determines the time-window in which its NMR signals are observable. For 13C 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 hyperpolarized 13C site. Here we tested this possible effect in a case where the protons are directly bound to an sp3 hyperpolarized 13C site (using [1,2-13C2]choline) and 1H-decoupling was applied continuously throughout the hyperpolarized decay measurement. We found that 1H-decoupling did not lead to any significant changes in the 13C polarization decay time but did result in the expected collapse of J-coupling and produced sharper signals. This result suggested that 1H-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 T1 of all investigated sites were calculated.
Bibliographical noteFunding Information:
This project has received funding from the European Research Council (ERC) under grant agreement No. 338040, from the European Union's Horizon 2020 research and innovation program under grant agreement No. 667192, and from the US National Science Foundation under grant agreement CHE 1710046. The authors thank Prof. Dr. Fedor Jelezko and Prof. Alex Retzker for useful discussions in the beginning of this study.
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- dynamic nuclear polarization
- polarization transfer
- proton decoupling