Frequency-agile gyrotron for electron decoupling and pulsed dynamic nuclear polarization

Scott, Faith J.; Saliba, Edward P.; Albert, Brice J.; Alaniva, Nicholas; Sesti, Erika L.; Gao, Chukun; Golota, Natalie; Choi, Eun A; Jagtap, Anil P.; Wittmann, J.; Eckardt, Michael; Harneit, Wolfgang; Corzilius, Björn; Sigurdsson, Snorri Th.; Barnes, Alexander B.

doi:10.1016/j.jmr.2018.02.010

Journal of Magnetic Resonance

2018

DOI: 10.1016/j.jmr.2018.02.010

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Frequency-agile gyrotron for electron decoupling and pulsed dynamic nuclear polarization

Faith J. Scott

Edward P. Saliba

Brice J. Albert

et al.

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Cited by 56 publications

(47 citation statements)

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“…[15][16][17][18] Often, sensitivity is also increased through the transfer of polarization from spins with stronger Zeeman interactions by radiofrequency [16,19] or microwave irradiation. [28,29] We have shown that chirped microwave pulses can partially decouple the electron-nuclear spin interaction after DNP in am ethod known as electron decoupling,w ith amore pronounced effect on observed nuclear spins in direct proximity to electron spins. [20][21][22][23][24][25] DNP transfer mechanisms require polarizing agents exhibiting electron paramagnetic resonance (EPR).…”

mentioning

confidence: 99%

“…[26] Here, we use as table organic monoradical, trityl (Finland radical), which has ar elatively narrow EPR lineshape. [28,29] We have shown that chirped microwave pulses can partially decouple the electron-nuclear spin interaction after DNP in am ethod known as electron decoupling,w ith amore pronounced effect on observed nuclear spins in direct proximity to electron spins. [28,29] We have shown that chirped microwave pulses can partially decouple the electron-nuclear spin interaction after DNP in am ethod known as electron decoupling,w ith amore pronounced effect on observed nuclear spins in direct proximity to electron spins.…”

mentioning

confidence: 99%

“…[27] Then arrow electron spin resonance and high-power microwave chirps generated by ac ustom-built frequency-agile gyrotron enable time-domain manipulation of electronic and hyperfine interactions. [28,29] We have shown that chirped microwave pulses can partially decouple the electron-nuclear spin interaction after DNP in am ethod known as electron decoupling,w ith amore pronounced effect on observed nuclear spins in direct proximity to electron spins. [30,31] DNP experiments typically require seconds to hours to spread enhanced polarization via nuclear spin diffusion to chemical sites of interest.…”

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confidence: 99%

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Electron Decoupling with Chirped Microwave Pulses for Rapid Signal Acquisition and Electron Saturation Recovery

et al. 2019

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Dynamic nuclear polarization (DNP) increases NMR sensitivity by transferring polarization from electron to nuclear spins.Herein, we demonstrate that electron decoupling with chirped microwave pulses enables improved observation of DNP-enhanced 13 Cs pins in direct dipolar contact with electron spins,t herebyl eading to an optimal delay between transients largely governed by relatively fast electron relaxation. We report the first measurement of electron longitudinal relaxation time (T 1e )d uring magic angle spinning (MAS) NMR by observation of DNP-enhanced NMR signals (T 1e = 40 AE 6ms, 40 mm trityl, 4.0 kHz MAS,4 .3 K). With a5ms DNP period, electron decoupling results in a195 %increase in signal intensity.MAS at 4.3 K, DNP,electron decoupling,and short recycle delays improve the sensitivity of 13 Cinthe vicinity of the polarizing agent. This is the first demonstration of recovery times between MAS-NMR transients being governed by short electron T 1 and fast DNP transfer.Magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy reveals structure and dynamics on ar ange of molecular architectures,i ncluding membrane proteins, [1][2][3][4][5][6] fibrils, [7][8][9][10] and interfaces. [11][12][13][14] Mechanical rotation of the sample about the magic angle of 54.78 8 with respect to the magnetic field partially averages anisotropic interactions of the magnetic resonance Hamiltonian, improving spectral resolution and sensitivity. [15][16][17][18] Often, sensitivity is also increased through the transfer of polarization from spins with stronger Zeeman interactions by radiofrequency [16,19] or microwave irradiation. In the case of dynamic nuclear polarization (DNP), hyperfine interactions are required to transfer spin polarization from electron to nuclear spins. [20][21][22][23][24][25] DNP transfer mechanisms require polarizing agents exhibiting electron paramagnetic resonance (EPR). [26] Here, we use as table organic monoradical, trityl (Finland radical), which has ar elatively narrow EPR lineshape. [27] Then arrow electron spin resonance and high-power microwave chirps generated by ac ustom-built frequency-agile gyrotron enable time-domain manipulation of electronic and hyperfine interactions. [28,29] We have shown that chirped microwave pulses can partially decouple the electron-nuclear spin interaction after DNP in am ethod known as electron decoupling,w ith amore pronounced effect on observed nuclear spins in direct proximity to electron spins. [30,31] DNP experiments typically require seconds to hours to spread enhanced polarization via nuclear spin diffusion to chemical sites of interest. [32][33][34] This slow spin diffusion significantly limits experiments.D NP is faster if nuclear spins proximal to the electron are polarized directly through hyperfine interactions.H owever,s uch direct DNP requires electron decoupling after the polarization transfer period to mitigate the detrimental effects of hyperfine interactions on NMR signatures. [31,35] Theo ptimal repetition time for direct DNP is li...

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confidence: 99%

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confidence: 99%

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Electron Decoupling with Chirped Microwave Pulses for Rapid Signal Acquisition and Electron Saturation Recovery

et al. 2019

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“…This figure was reproduced with modification with permission from the Journal of Magnetic Resonance. 53 Superimposed is the center frequency dependence of eDEC to demonstrate the location of the EPR spectrum of the radical (green). This figure was reproduced with modification with permission from the Journal of the American Chemical Society.…”

mentioning

confidence: 99%

“…Figure 5c shows a decrease in the output frequency when the accelerating voltage is increased. 53,54 …”

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confidence: 99%

Pulsed Electron Decoupling and Strategies for Time Domain Dynamic Nuclear Polarization with Magic Angle Spinning

Saliba

Sesti

Alaniva

et al. 2018

J. Phys. Chem. Lett.

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Magic angle spinning (MAS) dynamic nuclear polarization (DNP) is widely used to increase nuclear magnetic resonance (NMR) signal intensity. Frequency-chirped microwaves yield superior control of electron spins and are expected to play a central role in the development of DNP MAS experiments. Time domain electron control with MAS has considerable promise to improve DNP performance at higher fields and temperatures. We have recently demonstrated that pulsed electron decoupling using frequency-chirped microwaves improves MAS DNP experiments by partially attenuating detrimental hyperfine interactions. The continued development of pulsed electron decoupling will enable a new suite of MAS DNP experiments that transfer polarization directly to observed spins. Time domain DNP transfers to nuclear spins in conjunction with pulsed electron decoupling is described as a viable avenue toward DNP-enhanced, high-resolution NMR spectroscopy over a range of temperatures from <6 to 320 K.

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Observing Nearby Nuclei on Paramagnetic Trityls and MOFs via DNP and Electron Decoupling

Tan

Yang

Mardini

et al. 2022

Chemistry A European J

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Dynamic nuclear polarization (DNP) is an NMR sensitivity enhancement technique that mediates polarization transfer from unpaired electrons to NMR-active nuclei. Despite its success in elucidating important structural information on biological and inorganic materials, the detailed polarization-transfer pathway-from the electrons to the nearby and then the bulk solvent nuclei, and finally to the molecules of interest-remains unclear. In particular, the nuclei in the paramagnetic polarizing agent play significant roles in relaying the enhanced NMR polarizations to more remote nuclei. Despite their importance, the direct NMR observation of these nuclei is challenging because of poor sensitivity. Here, we show that a combined DNP and electron decoupling approach can facilitate direct NMR detection of these nuclei. We achieved an ~80 % improvement in NMR intensity via electron decoupling at 0.35 T and 80 K on trityl radicals. Moreover, we recorded a DNP enhancement factor of 𝜀 ~ 90 and ~11 % higher NMR intensity using electron decoupling on paramagnetic metal-organic framework, magnesium hexaoxytriphenylene (MgHOTP MOF).

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Frequency-agile gyrotron for electron decoupling and pulsed dynamic nuclear polarization

Cited by 56 publications

References 45 publications

Electron Decoupling with Chirped Microwave Pulses for Rapid Signal Acquisition and Electron Saturation Recovery

Electron Decoupling with Chirped Microwave Pulses for Rapid Signal Acquisition and Electron Saturation Recovery

Pulsed Electron Decoupling and Strategies for Time Domain Dynamic Nuclear Polarization with Magic Angle Spinning

Observing Nearby Nuclei on Paramagnetic Trityls and MOFs via DNP and Electron Decoupling

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