1
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Alaniva N, Saliba EP, Judge PT, Sesti EL, Harneit W, Corzilius B, Barnes AB. Electron-decoupled MAS DNP with N@C 60. Phys Chem Chem Phys 2023; 25:5343-5347. [PMID: 36734969 PMCID: PMC9930727 DOI: 10.1039/d2cp04516h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Frequency-chirped microwaves decouple electron- and 13C-spins in magic-angle spinning N@C60:C60 powder, improving DNP-enhanced 13C NMR signal intensity by 12% for 7 s polarization, and 5% for 30 s polarization. This electron decoupling demonstration is a step toward utilizing N@C60 as a controllable electron-spin source for magic-angle spinning magnetic resonance experiments.
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Affiliation(s)
- Nicholas Alaniva
- Laboratory of Physical Chemistry, ETH Zürich, Zürich 8093, Switzerland. .,Washington University in St. Louis, St. Louis 63130, MO, USA
| | - Edward P. Saliba
- Washington University in St. LouisSt. Louis 63130MOUSA,Massachusetts Institute of TechnologyCambridge 02139MAUSA
| | | | | | - Wolfgang Harneit
- Department of Physics, Universität OsnabrückOsnabrück 49076Germany
| | - Björn Corzilius
- Institute of Chemistry, Department Life, Light & Matter, Universität Rostock18059 RostockGermany
| | - Alexander B. Barnes
- Laboratory of Physical Chemistry, ETH ZürichZürich 8093Switzerland+41 44 633 43 81
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2
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Dai D, Wang X, Liu Y, Yang XL, Glaubitz C, Denysenkov V, He X, Prisner T, Mao J. Room-temperature dynamic nuclear polarization enhanced NMR spectroscopy of small biological molecules in water. Nat Commun 2021; 12:6880. [PMID: 34824218 PMCID: PMC8616939 DOI: 10.1038/s41467-021-27067-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 11/01/2021] [Indexed: 11/15/2022] Open
Abstract
Nuclear magnetic resonance (NMR) spectroscopy is a powerful and popular technique for probing the molecular structures, dynamics and chemical properties. However the conventional NMR spectroscopy is bottlenecked by its low sensitivity. Dynamic nuclear polarization (DNP) boosts NMR sensitivity by orders of magnitude and resolves this limitation. In liquid-state this revolutionizing technique has been restricted to a few specific non-biological model molecules in organic solvents. Here we show that the carbon polarization in small biological molecules, including carbohydrates and amino acids, can be enhanced sizably by in situ Overhauser DNP (ODNP) in water at room temperature and at high magnetic field. An observed connection between ODNP 13C enhancement factor and paramagnetic 13C NMR shift has led to the exploration of biologically relevant heterocyclic compound indole. The QM/MM MD simulation underscores the dynamics of intermolecular hydrogen bonds as the driving force for the scalar ODNP in a long-living radical-substrate complex. Our work reconciles results obtained by DNP spectroscopy, paramagnetic NMR and computational chemistry and provides new mechanistic insights into the high-field scalar ODNP.
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Affiliation(s)
- Danhua Dai
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Xianwei Wang
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
- College of Science, Zhejiang University of Technology, Hangzhou, Zhejiang, 310023, China
| | - Yiwei Liu
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China
| | - Xiao-Liang Yang
- Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Clemens Glaubitz
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
- Institute of Biophysical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Vasyl Denysenkov
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Xiao He
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China.
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai, 200062, China.
| | - Thomas Prisner
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany
| | - Jiafei Mao
- Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany.
- Institute of Biophysical Chemistry, Goethe University Frankfurt, 60438, Frankfurt am Main, Germany.
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3
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Wang Z, Hanrahan MP, Kobayashi T, Perras FA, Chen Y, Engelke F, Reiter C, Purea A, Rossini AJ, Pruski M. Combining fast magic angle spinning dynamic nuclear polarization with indirect detection to further enhance the sensitivity of solid-state NMR spectroscopy. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2020; 109:101685. [PMID: 32932182 DOI: 10.1016/j.ssnmr.2020.101685] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 07/24/2020] [Accepted: 07/28/2020] [Indexed: 06/11/2023]
Abstract
Dynamic nuclear polarization (DNP) and indirect detection are two commonly applied approaches for enhancing the sensitivity of solid-state NMR spectroscopy. However, their use in tandem has not yet been investigated. With the advent of low-temperature fast magic angle spinning (MAS) probes with 1.3-mm diameter rotors capable of MAS at 40 kHz it becomes feasible to combine these two techniques. In this study, we performed DNP-enhanced 2D indirectly detected heteronuclear correlation (idHETCOR) experiments on 13C, 15N, 113Cd and 89Y nuclei in functionalized mesoporous silica, CdS nanoparticles, and Y2O3 nanoparticles. The sensitivity of the 2D idHETCOR experiments was compared with those of DNP-enhanced directly-detected 1D cross polarization (CP) and 2D HETCOR experiments performed with a standard 3.2-mm rotor. Due to low CP polarization transfer efficiencies and large proton linewidth, the sensitivity gains achieved by indirect detection alone were lower than in conventional (non-DNP) experiments. Nevertheless, despite the smaller sample volume the 2D idHETCOR experiments showed better absolute sensitivities than 2D HETCOR experiments for nuclei with the lowest gyromagnetic ratios. For 89Y, 2D idHETCOR provided 8.2 times better sensitivity than the 1 D89Y-detected CP experiment performed with a 3.2-mm rotor.
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Affiliation(s)
- Zhuoran Wang
- U.S. DOE Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States; Department of Chemistry, Iowa State University, Ames, IA, 50011-3020, United States
| | - Michael P Hanrahan
- U.S. DOE Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States; Department of Chemistry, Iowa State University, Ames, IA, 50011-3020, United States
| | - Takeshi Kobayashi
- U.S. DOE Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States
| | - Frédéric A Perras
- U.S. DOE Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States
| | - Yunhua Chen
- U.S. DOE Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States; Department of Chemistry, Iowa State University, Ames, IA, 50011-3020, United States
| | | | | | - Armin Purea
- Bruker Biospin, 76287, Rheinstetten, Germany
| | - Aaron J Rossini
- U.S. DOE Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States; Department of Chemistry, Iowa State University, Ames, IA, 50011-3020, United States.
| | - Marek Pruski
- U.S. DOE Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States; Department of Chemistry, Iowa State University, Ames, IA, 50011-3020, United States.
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4
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Judge PT, Sesti EL, Alaniva N, Saliba EP, Price LE, Gao C, Halbritter T, Sigurdsson ST, Kyei GB, Barnes AB. Characterization of frequency-chirped dynamic nuclear polarization in rotating solids. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 313:106702. [PMID: 32203923 DOI: 10.1016/j.jmr.2020.106702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 01/18/2020] [Accepted: 02/21/2020] [Indexed: 06/10/2023]
Abstract
Continuous wave (CW) dynamic nuclear polarization (DNP) is used with magic angle spinning (MAS) to enhance the typically poor sensitivity of nuclear magnetic resonance (NMR) by orders of magnitude. In a recent publication we show that further enhancement is obtained by using a frequency-agile gyrotron to chirp incident microwave frequency through the electron resonance frequency during DNP transfer. Here we characterize the effect of chirped MAS DNP by investigating the sweep time, sweep width, center-frequency, and electron Rabi frequency of the chirps. We show the advantages of chirped DNP with a trityl-nitroxide biradical, and a lack of improvement with chirped DNP using AMUPol, a nitroxide biradical. Frequency-chirped DNP on a model system of urea in a cryoprotecting matrix yields an enhancement of 142, 21% greater than that obtained with CW DNP. We then go beyond this model system and apply chirped DNP to intact human cells. In human Jurkat cells, frequency-chirped DNP improves enhancement by 24% over CW DNP. The characterization of the chirped DNP effect reveals instrument limitations on sweep time and sweep width, promising even greater increases in sensitivity with further technology development. These improvements in gyrotron technology, frequency-agile methods, and in-cell applications are expected to play a significant role in the advancement of MAS DNP.
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Affiliation(s)
- Patrick T Judge
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States; Department of Biochemistry, Biophysics & Structural Biology, Washington University in St. Louis, St. Louis, MO 63110, United States
| | - Erika L Sesti
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States
| | - Nicholas Alaniva
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States
| | - Edward P Saliba
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States
| | - Lauren E Price
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States
| | - Chukun Gao
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States
| | - Thomas Halbritter
- Department of Chemistry, University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- Department of Chemistry, University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
| | - George B Kyei
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63130, United States; Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Accra, Ghana
| | - Alexander B Barnes
- Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland; Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, United States.
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5
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Judge PT, Sesti EL, Price LE, Albert BJ, Alaniva N, Saliba EP, Halbritter T, Sigurdsson ST, Kyei GB, Barnes AB. Dynamic Nuclear Polarization with Electron Decoupling in Intact Human Cells and Cell Lysates. J Phys Chem B 2020; 124:2323-2330. [DOI: 10.1021/acs.jpcb.9b10494] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Patrick T. Judge
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Department of Biochemistry, Biophysics & Structural Biology, Washington University in St. Louis, St. Louis, Missouri 63110, United States
| | - Erika L. Sesti
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Lauren E. Price
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Brice J. Albert
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Nicholas Alaniva
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Edward P. Saliba
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Thomas Halbritter
- Department of Chemistry, Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavik, Iceland
| | - Snorri Th. Sigurdsson
- Department of Chemistry, Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavik, Iceland
| | - George B. Kyei
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63130, United States
- Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana,
Legon, Accra 02233, Ghana
| | - Alexander B. Barnes
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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6
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Chen PH, Gao C, Barnes AB. Perspectives on microwave coupling into cylindrical and spherical rotors with dielectric lenses for magic angle spinning dynamic nuclear polarization. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 308:106518. [PMID: 31345770 DOI: 10.1016/j.jmr.2019.07.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 07/03/2019] [Accepted: 07/05/2019] [Indexed: 06/10/2023]
Abstract
Continuous wave dynamic nuclear polarization (DNP) increases the sensitivity of NMR, yet intense microwave fields are required to transition magic angle spinning (MAS) DNP to the time domain. Here we describe and analyze Teflon lenses for cylindrical and spherical MAS rotors that focus microwave power and increase the electron Rabi frequency, ν1s. Using a commercial simulation package, we solve the Maxwell equations and determine the propagation and focusing of millimeter waves (198 GHz). We then calculate the microwave intensity in a time-independent fashion to compute the ν1s. With a nominal microwave power input of 5 W, the average ν1s is 0.38 MHz within a 22 μL sample volume in a 3.2 mm outer diameter (OD) cylindrical rotor without a Teflon lens. Decreasing the sample volume to 3 μL and focusing the microwave beam with a Teflon lens increases the ν1s to 1.5 MHz. Microwave polarization and intensity perturbations associated with diffraction through the radiofrequency coil, losses from penetration through the rotor wall, and mechanical limitations of the separation between the lens and sample are significant challenges to improving microwave coupling in MAS DNP instrumentation. To overcome these issues, we introduce a novel focusing strategy using dielectric microwave lenses installed within spinning rotors. One such 9.5 mm OD cylindrical rotor assembly implements a Teflon focusing lens to increase the ν1s to 2.7 MHz within a 2 μL sample. Further, to access high spinning frequencies while also increasing ν1s, we analyze microwave coupling into MAS spheres. For 9.5 mm OD spherical rotors, we compute a ν1s of 0.36 MHz within a sample volume of 161 μL, and 2.5 MHz within a 3 μL sample placed at the focal point of a novel double lens insert. We conclude with an analysis and discussion of sub-millimeter diamond spherical rotors for time domain DNP at spinning frequencies >100 kHz. Sub-millimeter spherical rotors better overlap a tightly focused microwave beam, resulting in a ν1s of 2.2 MHz. Lastly, we propose that sub-millimeter dielectric spherical microwave resonators will provide a means to substantially improve electron spin control in the future.
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Affiliation(s)
- Pin-Hui Chen
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA; Department of Physics, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Chukun Gao
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
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7
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Saliba EP, Barnes AB. Fast electron paramagnetic resonance magic angle spinning simulations using analytical powder averaging techniques. J Chem Phys 2019; 151:114107. [PMID: 31542017 PMCID: PMC7043854 DOI: 10.1063/1.5113598] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 08/27/2019] [Indexed: 11/14/2022] Open
Abstract
Simulations describing the spin physics underpinning nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopy play an important role in the design of new experiments. When experiments are performed in the solid state, samples are commonly composed of powders or glasses, with molecules oriented at a large number of angles with respect to the laboratory frame. These powder angles must be represented in simulations to account for anisotropic interactions. Numerical techniques are typically used to accurately compute such powder averages. A large number of Euler angles are usually required, leading to lengthy simulation times. This is particularly true in broad spectra, such as those observed in EPR. The combination of the traditionally separate techniques of EPR and magic angle spinning (MAS) NMR could play an important role in future electron detected experiments, combined with dynamic nuclear polarization, which will allow for exceptional detection sensitivity of NMR spin coherences. Here, we present a method of reducing the required number of Euler angles in magnetic resonance simulations by analytically performing the powder average over one of the Euler angles in the static and MAS cases for the TEMPO nitroxide radical in a 7 T field. In the static case, this leads to a 97.5% reduction in simulation time over the fully numerical case and reproduces the expected spinning sideband manifold when simulated with a MAS frequency of 150 kHz. This technique is applicable to more traditional NMR experiments as well, such as those involving quadrupolar nuclei or multiple dimensions.
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Affiliation(s)
- Edward P Saliba
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, USA
| | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, USA
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8
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Carnahan SL, Venkatesh A, Perras FA, Wishart JF, Rossini AJ. High-Field Magic Angle Spinning Dynamic Nuclear Polarization Using Radicals Created by γ-Irradiation. J Phys Chem Lett 2019; 10:4770-4776. [PMID: 31347850 DOI: 10.1021/acs.jpclett.9b01655] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
High-field magic angle spinning dynamic nuclear polarization (MAS DNP) is often used to enhance the sensitivity of solid-state nuclear magnetic resonance experiments by transferring spin polarization from electron spins to nuclear spins. Here, we demonstrate that γ-irradiation induces the formation of stable radicals in inorganic solids, such as fused quartz and borosilicate glasses, as well as organic solids, such as glucose, cellulose, and a urea/polyethylene polymer. The radicals were then used to polarize 29Si or 1H spins in the core of some of these materials. Significant MAS DNP enhancements (ε) of more than 400 and 30 were obtained for fused quartz and glucose, respectively. For other samples, negligible values of ε were obtained, likely due to low concentrations of radicals or the presence of abundant quadrupolar spins. These results demonstrate that ionizing radiation is a promising alternative method for generating stable radicals that are suitable for high-field MAS DNP experiments.
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Affiliation(s)
- Scott L Carnahan
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Amrit Venkatesh
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Frédéric A Perras
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States
| | - James F Wishart
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Aaron J Rossini
- U.S. Department of Energy Ames Laboratory, Ames, Iowa 50011, United States
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
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9
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Griffin RG, Swager TM, Temkin RJ. High frequency dynamic nuclear polarization: New directions for the 21st century. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 306:128-133. [PMID: 31327537 PMCID: PMC6703937 DOI: 10.1016/j.jmr.2019.07.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Revised: 06/03/2019] [Accepted: 07/08/2019] [Indexed: 05/03/2023]
Affiliation(s)
- Robert G Griffin
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Dept. of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
| | - Timothy M Swager
- Dept. of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Richard J Temkin
- Plasma Science and Fusion Center and Dept. of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
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10
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Judge PT, Sesti EL, Saliba EP, Alaniva N, Halbritter T, Sigurdsson ST, Barnes AB. Sensitivity analysis of magic angle spinning dynamic nuclear polarization below 6 K. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 305:51-57. [PMID: 31212198 DOI: 10.1016/j.jmr.2019.05.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 05/28/2019] [Accepted: 05/30/2019] [Indexed: 06/09/2023]
Abstract
Dynamic nuclear polarization (DNP) improves signal-to-noise in nuclear magnetic resonance (NMR) spectroscopy. Signal-to-noise in NMR can be further improved with cryogenic sample cooling. Whereas MAS DNP is commonly performed between 25 and 110 K, sample temperatures below 6 K lead to further improvements in sensitivity. Here, we demonstrate that solid effect MAS DNP experiments at 6 K, using trityl, yield 3.2× more sensitivity compared to 90 K. Trityl with solid effect DNP at 6 K yields substantially more signal to noise than biradicals and cross effect DNP. We also characterize cross effect DNP with AMUPol and TEMTriPol-1 biradicals for DNP magic angle spinning at temperatures below 6 K and 7 Tesla. DNP enhancements determined from microwave on/off intensities are 253 from AMUPol and 49 from TEMTriPol-1. The higher thermal Boltzmann polarization at 6 K compared to 298 K, combined with these enhancements, should result in 10,000× signal gain for AMUPol and 2000× gain for TEMTriPol-1. However, we show that AMUPol reduces signal in the absence of microwaves by 90% compared to 41% by TEMTriPol-1 at 7 Tesla as the result of depolarization and other detrimental paramagnetic effects. AMUPol still yields the highest signal-to-noise improvement per unit time between the cross effect radicals due to faster polarization buildup (T1DNP = 4.3 s and 36 s for AMUPol and TEMTriPol-1, respectively). Overall, AMUPol results in 2.5× better sensitivity compared to TEMTriPol-1 in MAS DNP experiments performed below 6 K at 7 T. Trityl provides 6.0× more sensitivity than TEMTriPol-1 and 1.9× more than AMUPol at 6 K, thus yielding the greatest signal-to-noise per unit time among all three radicals. A DNP enhancement profile of TEMTriPol-1 recorded with a frequency-tunable custom-built gyrotron oscillator operating at 198 GHz is also included. It is determined that at 7 T below 6 K a microwave power level of 0.6 W incident on the sample is sufficient to saturate the cross effect mechanism using TEMTriPol-1, yet increasing the power level up to 5 W results in higher improvements in DNP sensitivity with AMUPol. These results indicate MAS DNP below 6 K will play a prominent role in ultra-sensitive NMR spectroscopy in the future.
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Affiliation(s)
- Patrick T Judge
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA; Department of Biochemistry, Biophysics & Structural Biology, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Erika L Sesti
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
| | - Edward P Saliba
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
| | - Nicholas Alaniva
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
| | - Thomas Halbritter
- Department of Chemistry, University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- Department of Chemistry, University of Iceland, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
| | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA.
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11
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Thureau P, Juramy M, Ziarelli F, Viel S, Mollica G. Brute-force solvent suppression for DNP studies of powders at natural isotopic abundance. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 99:15-19. [PMID: 30836289 DOI: 10.1016/j.ssnmr.2019.02.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 02/15/2019] [Accepted: 02/15/2019] [Indexed: 06/09/2023]
Abstract
A method based on highly concentrated radical solutions is investigated for the suppression of the NMR signals arising from solvents that are usually used for dynamic nuclear polarization experiments. The presented method is suitable in the case of powders, which are impregnated with a radical-containing solution. It is also demonstrated that the intensity and the resolution of the signals due to the sample of interest is not affected by the high concentration of radicals. The method proposed here is therefore valuable when sensitivity is of the utmost importance, namely samples at natural isotopic abundance.
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Affiliation(s)
| | - Marie Juramy
- Aix Marseille Univ, CNRS, ICR, Marseille, France
| | - Fabio Ziarelli
- Aix Marseille Univ, CNRS, Centrale Marseille, FSCM, Marseille, France
| | - Stephane Viel
- Aix Marseille Univ, CNRS, ICR, Marseille, France; Institut Universitaire de France, Paris, France
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12
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Alaniva N, Saliba EP, Sesti EL, Judge PT, Barnes AB. Electron Decoupling with Chirped Microwave Pulses for Rapid Signal Acquisition and Electron Saturation Recovery. Angew Chem Int Ed Engl 2019; 58:7259-7262. [DOI: 10.1002/anie.201900139] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 03/01/2019] [Indexed: 11/07/2022]
Affiliation(s)
- Nicholas Alaniva
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
| | - Edward P. Saliba
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
| | - Erika L. Sesti
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
| | - Patrick T. Judge
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
- Department of Biochemistry, Biophysics, and Biology Washington University in St. Louis School of Medicine 660 S. Euclid Ave St Louis MO 63110 USA
| | - Alexander B. Barnes
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
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13
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Alaniva N, Saliba EP, Sesti EL, Judge PT, Barnes AB. Electron Decoupling with Chirped Microwave Pulses for Rapid Signal Acquisition and Electron Saturation Recovery. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201900139] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Nicholas Alaniva
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
| | - Edward P. Saliba
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
| | - Erika L. Sesti
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
| | - Patrick T. Judge
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
- Department of Biochemistry, Biophysics, and Biology Washington University in St. Louis School of Medicine 660 S. Euclid Ave St Louis MO 63110 USA
| | - Alexander B. Barnes
- Department of Chemistry Washington University in St. Louis One Brookings Drive St. Louis MO 63130 USA
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14
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Vioglio PC, Thureau P, Juramy M, Ziarelli F, Viel S, Williams PA, Hughes CE, Harris KDM, Mollica G. A Strategy for Probing the Evolution of Crystallization Processes by Low-Temperature Solid-State NMR and Dynamic Nuclear Polarization. J Phys Chem Lett 2019; 10:1505-1510. [PMID: 30882228 DOI: 10.1021/acs.jpclett.9b00306] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Crystallization plays an important role in many areas, and to derive a fundamental understanding of crystallization processes, it is essential to understand the sequence of solid phases produced as a function of time. Here, we introduce a new NMR strategy for studying the time evolution of crystallization processes, in which the crystallizing system is quenched rapidly to low temperature at specific time points during crystallization. The crystallized phase present within the resultant "frozen solution" may be investigated in detail using a range of sophisticated NMR techniques. The low temperatures involved allow dynamic nuclear polarization (DNP) to be exploited to enhance the signal intensity in the solid-state NMR measurements, which is advantageous for detection and structural characterization of transient forms that are present only in small quantities. This work opens up the prospect of studying the very early stages of crystallization, at which the amount of solid phase present is intrinsically low.
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Affiliation(s)
| | - Pierre Thureau
- Aix Marseille Univ, CNRS, ICR , 13397 Marseille , France
| | - Marie Juramy
- Aix Marseille Univ, CNRS, ICR , 13397 Marseille , France
| | - Fabio Ziarelli
- Aix Marseille Univ, CNRS, Centrale Marseille, FSCM , 13397 Marseille , France
| | - Stéphane Viel
- Aix Marseille Univ, CNRS, ICR , 13397 Marseille , France
- Institut Universitaire de France , 75231 Paris , France
| | - P Andrew Williams
- School of Chemistry , Cardiff University , Park Place , Cardiff , Wales CF10 3AT , U.K
| | - Colan E Hughes
- School of Chemistry , Cardiff University , Park Place , Cardiff , Wales CF10 3AT , U.K
| | - Kenneth D M Harris
- School of Chemistry , Cardiff University , Park Place , Cardiff , Wales CF10 3AT , U.K
| | - Giulia Mollica
- Aix Marseille Univ, CNRS, ICR , 13397 Marseille , France
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