High-Field Dynamic Nuclear Polarization for Solid and Solution Biological NMR

Barnes, Alexander B.; Paëpe, Gaël De; Wel, Patrick C.A. van der; Hu, Kan‐Nian; Joo, Chan-Gyu; Bajaj, Vikram S.; Mak‐Jurkauskas, Melody L.; Sirigiri, J.R.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

doi:10.1007/s00723-008-0129-1

Cited by 323 publications

(256 citation statements)

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“…These approaches have resulted in large signal enhancements and have enabled many experiments that would otherwise be impossible. [19][20][21][22][23] by Overhauser 25 and confirmed by Carver and Slichter, 26 has not been identified or utilized during the course of this renaissance. Although the possibility of an OE in insulator was discussed by Abragam, 27 the conventional wisdom is that Overhauser DNP is important only in systems with mobile electrons such as conductors (metals and low dimensional conductors) or in liquid solution.…”

mentioning

confidence: 95%

“…These approaches have resulted in large signal enhancements and have enabled many experiments that would otherwise be impossible. [19][20][21][22][23] Nevertheless, with the exception of an early example on a 1D conductor, 24 the Overhauser effect (OE), which was the initial DNP mechanism proposed a) Current address: Institute for Physical and Theoretical Chemistry, Institute for Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany.…”

Section: Introductionmentioning

confidence: 99%

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Overhauser effects in insulating solids

Can

Caporini

Mentink-Vigier

et al. 2014

The Journal of Chemical Physics

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We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/water matrices. The 1 H DNP enhancement field profiles of the BDPA radicals exhibit a significant DNP Overhauser effect (OE) as well as a solid effect (SE) despite the fact that these samples are insulating solids. In contrast, trityl exhibits only a SE enhancement. Data suggest that the appearance of the OE is due to rather strong electron-nuclear hyperfine couplings present in BDPA and SA-BDPA, which are absent in trityl and perdeuterated BDPA (d 21 -BDPA). In addition, and in contrast to other DNP mechanisms such as the solid effect or cross effect, the experimental data suggest that the OE in non-conducting solids scales favorably with magnetic field, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. Simulations using a model two spin system consisting of an electron hyperfine coupled to a 1 H reproduce the essential features of the field profiles and indicate that the OE in these samples originates from the zero and double quantum cross relaxation induced by fluctuating hyperfine interactions between the intramolecular delocalized unpaired electrons and their neighboring nuclei, and that the size of these hyperfine couplings is crucial to the magnitude of the enhancements. Microwave power dependent studies show that the OE saturates at considerably lower power levels than the solid effect in the same samples. Our results provide new insights into the mechanism of the Overhauser effect, and also provide a new approach to perform DNP experiments in chemical, biophysical, and physical systems at high magnetic fields. INTRODUCTIONThe last decade has witnessed a renaissance in the use of high frequency dynamic nuclear polarization (DNP) to enhance sensitivity in nuclear magnetic resonance (NMR) experiments. In particular, the development of gyrotron and other high frequency microwave sources permits DNP to be performed at magnetic fields used in contemporary NMR experiments (5-20 T). 1-8 To date these experiments, which have focused mostly on insulating solids formed from glassy, frozen solutions of proteins and other nonconducting materials, have relied primarily on narrow line monoradicals and the solid effect (SE) 1, 9-11 or nitroxide biradicals and the cross effect (CE) [12][13][14][15][16][17][18] to mediate the polarization process. These approaches have resulted in large signal enhancements and have enabled many experiments that would otherwise be impossible. [19][20][21][22][23] by Overhauser 25 and confirmed by Carver and Slichter, 26 has not been identified or utilized during the course of this renaissance. Although the possibility of an OE in insulator was discussed by Abragam, 27 the conventional wisdom is that Overhauser DNP is important only in systems with mobile electrons ...

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mentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Overhauser effects in insulating solids

Can

Caporini

Mentink-Vigier

et al. 2014

The Journal of Chemical Physics

Self Cite

172

226

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“…14,[17][18][19] Single crystals were harvested and polished to fit into a quartz capillary of 0.4 mm inner diameter for experiments at 5 T. For experiments at 0.35 T, a larger sample that fit into a 4 mm EPR sample tube was used. In order to suppress the 1 H NMR signal from trapped solvent, we used perdeuterated ethanol (Cambridge Isotope).…”

Section: Experimental Samplesmentioning

confidence: 99%

“…12 Initially, the primary application of DNP was preparation of polarized targets for neutron scattering experiments; 13 however, over the past decade, DNP has been used extensively to enhance the inherently low sensitivity of nuclear magnetic resonance (NMR) signals. [14][15][16][17][18][19] Enhancements on the order of 10 2 − 10 3 were made possible via the solid effect using narrow-line radicals 20-23 and cross effect using biradicals 24-27 as polarizing agents and high frequency gyrotrons as microwave sources. [28][29][30] The latter operate in the 140-560 GHz regime and enable DNP to be performed at magnet field strengths used in contemporary NMR experiments (5-20 T).…”

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Time domain DNP with the NOVEL sequence

Can

Walish

Swager

et al. 2015

The Journal of Chemical Physics

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We present results of a pulsed dynamic nuclear polarization (DNP) study at 0.35 T (9.7 GHz/ 14.7 MHz for electron/ 1 H Larmor frequency) using a lab frame-rotating frame cross polarization experiment that employs electron spin locking fields that match the 1 H nuclear Larmor frequency, the so called NOVEL (nuclear orientation via electron spin locking) condition. We apply the method to a series of DNP samples including a single crystal of diphenyl nitroxide (DPNO) doped benzophenone (BzP), 1,3-bisdiphenylene-2-phenylallyl (BDPA) doped polystyrene (PS), and sulfonated-BDPA (SA-BDPA) doped glycerol/water glassy matrices. The optimal Hartman-Hahn matching condition is achieved when the nutation frequency of the electron matches the Larmor frequency of the proton, ω 1S = ω 0I , together with possible higher order matching conditions at lower efficiencies. The magnetization transfer from electron to protons occurs on the time scale of ∼100 ns, consistent with the electron-proton couplings on the order of 1-10 MHz in these samples. In a fully protonated single crystal DPNO/BzP, at 270 K, we obtained a maximum signal enhancement of ε = 165 and the corresponding gain in sensitivity of ε(T 1 /T B ) 1/2 = 230 due to the reduction in the buildup time under DNP. In a sample of partially deuterated PS doped with BDPA, we obtained an enhancement of 323 which is a factor of ∼3.2 higher compared to the protonated version of the same sample and accounts for 49% of the theoretical limit. For the SA-BDPA doped glycerol/water glassy matrix at 80 K, the sample condition used in most applications of DNP in nuclear magnetic resonance, we also observed a significant enhancement. Our findings demonstrate that pulsed DNP via the NOVEL sequence is highly efficient and can potentially surpass continuous wave DNP mechanisms such as the solid effect and cross effect which scale unfavorably with increasing magnetic field. Furthermore, pulsed DNP is also a promising avenue for DNP at high temperature. C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4927087] INTRODUCTIONDynamic nuclear polarization (DNP) is a process whereby the large polarization present in an electron spin reservoir of a paramagnetic polarizing agent is transferred via microwave irradiation to nuclei, thereby enhancing the nuclear spin polarization. The initial mechanism supporting the DNP process, the Overhauser effect (OE), was proposed in 1953 1 and confirmed experimentally 2,3 in samples with mobile electrons (i.e., metals, solutions, and 1D conductors). In contrast, in insulating solids, such as glycerol/water glasses and biological samples, the OE was thought to be forbidden, but we have recently observed Overhauser enhancements using polarizing agents with narrow EPR spectra that exhibit strong 1 H−e − hyperfine couplings. 4 Furthermore, in these sorts of samples, DNP processes can also be mediated by three other mechanisms -the solid effect (SE), 5,6 the cross effect, 7-11 and/or thermal mixing. 12 Initially, the primary application of DNP was preparation of p...

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“…For example, the presence of the optical excitation in this class of system may facilitate dynamic nuclear polarization [20,21]. Further, recent experiments have shown that the principal decoherence mechanism for nuclear spins that are controlled through their interaction with electron spins is caused by that very same interaction [22].…”

Section: Introductionmentioning

confidence: 99%

Creating nuclear spin entanglement using an optical degree of freedom

2011

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Molecular nanostructures are promising building blocks for future quantum technologies, provided methods of harnessing their multiple degrees of freedom can be identified and implemented. Due to low decoherence rates, nuclear spins are considered ideal candidates for storing quantum information, while optical excitations can give rise to fast and controllable interactions for information processing. A recent paper [M. Schaffry et al., Phys. Rev. Lett. 104, 200501 (2010)] proposed a method for entangling two nuclear spins through their mutual coupling to a transient optically excited electron spin. Building on the same idea, we present here an extended and much more detailed theoretical framework, showing that this method is in fact applicable to a much wider class of molecular structures than previously discussed in the original proposal.

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High-Field Dynamic Nuclear Polarization for Solid and Solution Biological NMR

Cited by 323 publications

References 58 publications

Overhauser effects in insulating solids

Overhauser effects in insulating solids

Time domain DNP with the NOVEL sequence

Creating nuclear spin entanglement using an optical degree of freedom

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