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

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

doi:10.1021/acs.jpclett.0c01473

Cited by 10 publications

(13 citation statements)

References 55 publications

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“…This diminishes the flow of electron Zeeman energy and disfavours the CE compared to TM. These findings are consistent with the observation of TM while polarizing proton spins using the radical BDPA at 2.5 T and polarizing 13 C spins at 6.7 T, which is significantly smaller than the trityl OX063Me and exhibits a narrow ESR spectrum [9,31]. Future work will be aimed at extending this treatment to include the actual ESR lineshape of radicals used for DNP.…”

Section: Discussionsupporting

confidence: 84%

Electron Spin–Spin Interactions in DNP: Thermal Mixing vs. the Cross Effect

Wenckebach

2021

Appl Magn Reson

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The spectrum of the electron spin-spin interactions largely determines the mechanism that governs dynamic nuclear polarization (DNP). A narrow spectrum favours the solid effect (SE). A broader spectrum brings the cross effect (CE) into play-that is an exchange of electron Zeeman energy with the nuclear spins-and a very broad spectrum also thermal mixing (TM)-that is an exchange of electron spinspin interaction energy with the nuclear spins. A previous article described Monte Carlo simulations of the spectrum of these interactions for approximately spherical radicals in glasses and showed that this spectrum is best described by a Lorentzian that is smoothly cut-off by a broad Gaussian. That work also provided analytical approximations for the lower moments of the spectrum and the width of the Gaussian cut-off. Here we extend that work with the derivation of an analytical approximation for the width of the Lorentzian and use the result to determine the relative strengths of the energy flows due to the CE and TM as function of the diameter of the radicals, their concentration and the magnetic field.

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Section: Discussionsupporting

confidence: 84%

Electron Spin–Spin Interactions in DNP: Thermal Mixing vs. the Cross Effect

Wenckebach

2021

Appl Magn Reson

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“…This TM mechanism is also reproduced in 40 mM BDPA in OTP at higher temperature (150 K), resulting in an enhancement of 19 using 350 mW of μw irradiation power (Figure S6). In fact, TM of 13 C DNP has been reported by Becerra et al in 1993 for 2 wt % BDPA in PS at 5 T and recently by Radaelli et al for 60 mM and 120 mM SA BDPA in a water/glycerol mixture at 6.7 T, suggesting that the spatial distribution of such a BDPA spin system can lead to TM DNP already. Although the possibilities of 1 H TM DNP of BDPA in PS or SA-BDPA in a water/glycerol mixture have not been examined, we are confident to propound that it is the same TM DNP mechanism arising at the BDPA EPR center transition for 1 H DNP of BDPA in PS and SA-BDPA in water/glycerol.…”

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confidence: 79%

¹H Thermal Mixing Dynamic Nuclear Polarization with BDPA as Polarizing Agents

Equbal

Tabassum

Han

2020

J. Phys. Chem. Lett.

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Dynamic Nuclear Polarization (DNP) is a sensitivity enhancing technique for Nuclear Magnetic Resonance. A recent discovery of Overhauser Effect (OE) DNP in insulating systems under cryogenic conditions using 1,3-bisdiphenylene-2-phenylallyl (BDPA) as the polarizing agent (PA) has caught attention due to its promising DNP performance at a high magnetic field and under fast magic angle spinning conditions. However, the mechanism of OE in insulating-solids/BDPA is unclear. We present an alternative explanation that the dominant underlying DNP mechanism of BDPA is Thermal Mixing (TM). This is ascertained with the discovery that TM effect is enhanced by multi-electron spin coupling, which is corroborated by an asymmetric electron paramagnetic resonance line shape signifying the coexistence of clustered and isolated BDPA species, and by hyperpolarized electron spin populations giving rise to an electron spin polarization gradient which are characteristic signatures of TM DNP. Finally, quantum mechanical simulations using spatially asymmetrically coupled three electron spins and a nuclear spin demonstrate that triple-flip DNP, with hyperfine fluctuations turned off, can yield the 1 H DNP profile as observed with BDPA. Clarifying the DNP mechanism is critical to develop design principles for optimizing the PA for achieving optimal DNP efficiency.

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“…Here, the population difference of the energy states of spins in a magnetic field is dramatically increased. This method leads to unprecedented signal to noise enhancements [3–7] and can achieve 10 % polarization or more [8, 9] . To put these numbers into context: 10 % 13 C polarization is equivalent to a signal enhancement of 10 000‐fold at 11.7 T or about 100 000‐fold at 1.5 T.…”

Section: Introductionmentioning

confidence: 99%

“…This method leads to unprecedented signal to noise enhancements [3][4][5][6][7] and can achieve 10 %p olarization or more. [8,9] To put these numbers into context:1 0% 13 Cp olarization is equivalent to as ignal enhancement of 10 000-fold at 11.7 Torabout 100 000-fold at 1.5 T.…”

Section: Introductionmentioning

confidence: 99%

Parahydrogen‐Induced Polarization of Amino Acids

et al. 2021

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Nuclear magnetic resonance (NMR) has become a universal method for biochemical and biomedical studies, including metabolomics, proteomics, and magnetic resonance imaging (MRI). By increasing the signal of selected molecules, the hyperpolarization of nuclear spin has expanded the reach of NMR and MRI even further (e.g. hyperpolarized solid‐state NMR and metabolic imaging in vivo). Parahydrogen (pH2) offers a fast and cost‐efficient way to achieve hyperpolarization, and the last decade has seen extensive advances, including the synthesis of new tracers, catalysts, and transfer methods. The portfolio of hyperpolarized molecules now includes amino acids, which are of great interest for many applications. Here, we provide an overview of the current literature and developments in the hyperpolarization of amino acids and peptides.

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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

Cited by 10 publications

References 55 publications

Electron Spin–Spin Interactions in DNP: Thermal Mixing vs. the Cross Effect

Electron Spin–Spin Interactions in DNP: Thermal Mixing vs. the Cross Effect

¹H Thermal Mixing Dynamic Nuclear Polarization with BDPA as Polarizing Agents

Parahydrogen‐Induced Polarization of Amino Acids

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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

Cited by 10 publications

References 55 publications

Electron Spin–Spin Interactions in DNP: Thermal Mixing vs. the Cross Effect

Electron Spin–Spin Interactions in DNP: Thermal Mixing vs. the Cross Effect

1H Thermal Mixing Dynamic Nuclear Polarization with BDPA as Polarizing Agents

Parahydrogen‐Induced Polarization of Amino Acids

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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

¹H Thermal Mixing Dynamic Nuclear Polarization with BDPA as Polarizing Agents