Effect of electron spin dynamics on solid-state dynamic nuclear polarization performance

Siaw, Ting Ann; Fehr, Matthias; Lund, Alicia; Latimer, Allegra A.; Walker, Shamon A.; Edwards, Devin T.; Han, Songi

doi:10.1039/c4cp02013h

Cited by 49 publications

(114 citation statements)

References 52 publications

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“…In contrast to the measured distances between SL-lipid nitroxide moieties, a 10 mM solution of nitroxide monoradicals has an average distance of 30 Å between radicals, nearly 3× longer than the measured distance (10 Å) for 3.0 mol% 7-Doxyl-PC. 49 This dramatic decrease in distance between similar spin concentrations of SL-lipids compared to monoradicals in solution is not unexpected as the monoradicals are homogenously dispersed throughout the sample while SL-lipids are effectively constrained to a two-dimensional lattice that is the lipid bilayer. This constraint to a planar lipid bilayer results in a stronger intermolecular electron-electron dipolar coupling that is manifested in the broadened EPR spectra.…”

Section: Discussionmentioning

confidence: 90%

Molecular Rationale for Improved Dynamic Nuclear Polarization of Biomembranes

et al. 2016

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Dynamic nuclear polarization (DNP) enhanced solid-state NMR can provide orders of magnitude in signal enhancement. One of the most important aspects of obtaining efficient DNP enhancements is the optimization of the paramagnetic polarization agents used. To date, the most utilized polarization agents are nitroxide biradicals. However, the efficiency of these polarization agents is diminished when used with samples other than small molecule model compounds. We recently demonstrated the effectiveness of nitroxide labeled lipids as polarization agents for lipids and a membrane embedded peptide. Here, we systematically characterize, via electron paramagnetic (EPR), the dynamics of and the dipolar couplings between nitroxide labeled lipids under conditions relevant to DNP applications. Complemented by DNP enhanced solid-state NMR measurements at 600 MHz/395 GHz, a molecular rationale for the efficiency of nitroxide labeled lipids as DNP polarization agents is developed. Specifically, optimal DNP enhancements are obtained when the nitroxide moiety is attached to the lipid choline head group and local nitroxide concentrations yield an average e−-e− dipolar coupling of 47 MHz. Based on these measurements, we propose a framework for development of DNP polarization agents optimal for membrane protein structure determination.

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Section: Discussionmentioning

confidence: 90%

Molecular Rationale for Improved Dynamic Nuclear Polarization of Biomembranes

et al. 2016

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“…At 7 T, the inhomogeneously broadened nitroxide lineshape simulated with EasySpin [44] is approximately 750 MHz broad [45]. The γ S B 1 S frequency required to control this lineshape with a short (~1 ns) hard pulse is thus ~750 MHz and would require an | E 0 | value of 4.5 × 10 7 V/m, which corresponds to a microwave input power of 13 MW.…”

Section: Experimental Considerations For Mas Pulsed Dnpmentioning

confidence: 99%

Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization

Hoff

Albert

Saliba

et al. 2015

Solid State Nuclear Magnetic Resonance

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Hyperfine decoupling and pulsed dynamic nuclear polarization (DNP) are promising techniques to improve high field DNP NMR. We explore experimental and theoretical considerations to implement them with magic angle spinning (MAS). Microwave field simulations using the high frequency structural simulator (HFSS) software suite are performed to characterize the inhomogeneous phase independent microwave field throughout a 198 GHz MAS DNP probe. Our calculations show that a microwave power input of 17 W is required to generate an average EPR nutation frequency of 0.84 MHz. We also present a detailed calculation of microwave heating from the HFSS parameters and find that 7.1% of the incident microwave power contributes to dielectric sample heating. Voltage tunable gyrotron oscillators are proposed as a class of frequency agile microwave sources to generate microwave frequency sweeps required for the frequency modulated cross effect, electron spin inversions, and hyperfine decoupling. Electron spin inversions of stable organic radicals are simulated with SPINEVOLUTION using the inhomogeneous microwave fields calculated by HFSS. We calculate an electron spin inversion efficiency of 56% at a spinning frequency of 5 kHz. Finally, we demonstrate gyrotron acceleration potentials required to generate swept microwave frequency profiles for the frequency modulated cross effect and electron spin inversions.

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“…corresponds to the electron T 1 while the shorter corresponds to the relaxation effects contributed by electron-electron cross relaxation effects. 61,62 Electron T −1 1 was plotted vs. temperature on a log-log plot (Fig. 2(b)), and a power law equation (T −1 1 = AT α ) was fitted to the data.…”

Section: A Epr Of Trityl Doped With Ln 3+mentioning

confidence: 99%

Influence of Dy3+ and Tb3+ doping on 13C dynamic nuclear polarization

Niedbalski

Parish

Kiswandhi

et al. 2017

The Journal of Chemical Physics

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Dynamic nuclear polarization (DNP) is a technique that uses a microwave-driven transfer of high spin alignment from electrons to nuclear spins. This is most effective at low temperature and high magnetic field, and with the invention of the dissolution method, the amplified nuclear magnetic resonance (NMR) signals in the frozen state in DNP can be harnessed in the liquid-state at physiologically acceptable temperature for in vitro and in vivo metabolic studies. A current optimization practice in dissolution DNP is to dope the sample with trace amounts of lanthanides such as Gd 3+ or Ho 3+ , which further improves the polarization. While Gd 3+ and Ho 3+ have been optimized for use in dissolution DNP, other lanthanides have not been exhaustively studied for use in 13 C DNP applications. In this work, two additional lanthanides with relatively high magnetic moments, Dy 3+ and Tb 3+ , were extensively optimized and tested as doping additives for 13 C DNP at 3.35 T and 1.2 K. We have found that both of these lanthanides are also beneficial additives, to a varying degree, for 13 C DNP. The optimal concentrations of Dy 3+ (1.5 mM) and Tb 3+ (0.25 mM) for 13 C DNP were found to be less than that of Gd 3+ (2 mM). W-band electron paramagnetic resonance shows that these enhancements due to Dy 3+ and Tb 3+ doping are accompanied by shortening of electron T 1 of trityl OX063 free radical. Furthermore, when dissolution was employed, Tb 3+ -doped samples were found to have similar liquid-state 13 C NMR signal enhancements compared to samples doped with Gd 3+ , and both Tb 3+ and Dy 3+ had a negligible liquid-state nuclear T 1 shortening effect which contrasts with the significant reduction in T 1 when using Gd 3+ . Our results show that Dy 3+ doping and Tb 3+ doping have a beneficial impact on 13 C DNP both in the solid and liquid states, and that Tb 3+ in particular could be used as a potential alternative to Gd 3+ in 13 C dissolution DNP experiments. Published by AIP Publishing.

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Effect of electron spin dynamics on solid-state dynamic nuclear polarization performance

Cited by 49 publications

References 52 publications

Molecular Rationale for Improved Dynamic Nuclear Polarization of Biomembranes

Molecular Rationale for Improved Dynamic Nuclear Polarization of Biomembranes

Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization

Influence of Dy3+ and Tb3+ doping on 13C dynamic nuclear polarization

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