1
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Nir-Arad O, Shlomi DH, Israelstam A, Amit T, Manukovsky N, Fialkov AB, Kaminker I. The CW-EPR Capabilities of a Dual DNP/EPR Spectrometer Operating at 14 and 7 T. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 360:107635. [PMID: 38401475 DOI: 10.1016/j.jmr.2024.107635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 12/24/2023] [Accepted: 02/07/2024] [Indexed: 02/26/2024]
Abstract
High-field electron paramagnetic resonance (EPR) measurements are indispensable for a better understanding of dynamic nuclear polarization (DNP), which relies on polarization transfer between electron and nuclear spins. DNP experiments are typically performed at high > 7 T magnetic fields and low ≤ 100 K temperatures, while EPR instrumentation capable of EPR measurements under these conditions is scarce. In this paper, we describe the CW EPR capabilities of a dual DNP/EPR spectrometer that is designed to carry out EPR experiments under "DNP conditions" at 14 and 7 T. In the first part, we present the design of this instrument, highlighting the choices made to allow for both DNP and EPR operations. The spectrometer uses a sweepable cryogen-free magnet with NMR-grade homogeneity, a closed-cycle cooling system, a quasi-optical induction mode bridge, and a superheterodyne receiver system. The probe design is optimized for low heat load and fast sample exchange under cryogenic conditions. The spectrometer can operate in frequency and field sweep modes, including wide field sweeps using the main coil of the magnet. In the second part, we present EPR spectra acquired over a wide range of samples and operating conditions, illustrating the CW EPR capabilities of the instrument.
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Affiliation(s)
- Orit Nir-Arad
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - David H Shlomi
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Amit Israelstam
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Tomer Amit
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Nurit Manukovsky
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Alexander B Fialkov
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Ilia Kaminker
- School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel.
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2
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Chen PH, Gao C, Alaniva N, Björgvinsdóttir S, Pagonakis IG, Urban MA, Däpp A, Gunzenhauser R, Barnes AB. Watch-sized 12 Tesla all-high-temperature-superconducting magnet. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 357:107588. [PMID: 37976810 DOI: 10.1016/j.jmr.2023.107588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 11/06/2023] [Accepted: 11/09/2023] [Indexed: 11/19/2023]
Abstract
We demonstrate the construction of 7 Tesla and 12 Tesla all high-temperature-superconducting (HTS) magnets, small enough to fit on your wrist. The size of the magnet reduces the cost of fabrication, decreases the fringe field to permit facile siting of magnets, and decreases the stored energy of high field magnets. These small HTS-based magnets are being developed for gyrotron microwave sources for use in high-field nuclear magnetic resonance applications. The 7 Tesla and 12 Tesla magnets employ a no-insulation winding technique and are cooled to 4.2 Kelvin in a liquid helium cryostat. The 7 Tesla magnet is a single pancake coil, made of only 9.4 m of HTS tape, with an inner diameter of 8 mm and an outer diameter of 24 mm. This magnet was charged up to 1168 Amperes, generating a field of 7.3 Tesla. The 12 Tesla magnet is comprised of two pancake coils (inner diameter of 10 mm and outer diameter of 27 mm) connected in series. This magnet reached its maximum field at a current of 850 Amperes.
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Affiliation(s)
- Pin-Hui Chen
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland.
| | - Chukun Gao
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland
| | - Nicholas Alaniva
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland
| | - Snædís Björgvinsdóttir
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland
| | - Ioannis Gr Pagonakis
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland
| | - Michael A Urban
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland
| | - Alexander Däpp
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland
| | - Ronny Gunzenhauser
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland
| | - Alexander B Barnes
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2 8093, Zürich, Switzerland.
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3
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Zhao Y, El Mkami H, Hunter RI, Casano G, Ouari O, Smith GM. Large cross-effect dynamic nuclear polarisation enhancements with kilowatt inverting chirped pulses at 94 GHz. Commun Chem 2023; 6:171. [PMID: 37607991 PMCID: PMC10444895 DOI: 10.1038/s42004-023-00963-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 07/25/2023] [Indexed: 08/24/2023] Open
Abstract
Dynamic nuclear polarisation (DNP) is a process that transfers electron spin polarisation to nuclei by applying resonant microwave radiation, and has been widely used to improve the sensitivity of nuclear magnetic resonance (NMR). Here we demonstrate new levels of performance for static cross-effect proton DNP using high peak power chirped inversion pulses at 94 GHz to create a strong polarisation gradient across the inhomogeneously broadened line of the mono-radical 4-amino TEMPO. Enhancements of up to 340 are achieved at an average power of a few hundred mW, with fast build-up times (3 s). Experiments are performed using a home-built wideband kW pulsed electron paramagnetic resonance (EPR) spectrometer operating at 94 GHz, integrated with an NMR detection system. Simultaneous DNP and EPR characterisation of other mono-radicals and biradicals, as a function of temperature, leads to additional insights into limiting relaxation mechanisms and give further motivation for the development of wideband pulsed amplifiers for DNP at higher frequencies.
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Affiliation(s)
- Yujie Zhao
- School of Physics and Astronomy, University of St Andrews, KY16 9SS, Fife, Scotland
| | - Hassane El Mkami
- School of Physics and Astronomy, University of St Andrews, KY16 9SS, Fife, Scotland
| | - Robert I Hunter
- School of Physics and Astronomy, University of St Andrews, KY16 9SS, Fife, Scotland
| | - Gilles Casano
- Aix Marseille University, CNRS, ICR, UMR 7273, F-13013, Marseille, France
| | - Olivier Ouari
- Aix Marseille University, CNRS, ICR, UMR 7273, F-13013, Marseille, France
| | - Graham M Smith
- School of Physics and Astronomy, University of St Andrews, KY16 9SS, Fife, Scotland.
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4
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Golota NC, Fredin ZP, Banks DP, Preiss D, Bahri S, Patil P, Langford WK, Blackburn CL, Strand E, Michael B, Dastrup B, Nelson KA, Gershenfeld N, Griffin R. Diamond rotors. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 352:107475. [PMID: 37224586 PMCID: PMC10504678 DOI: 10.1016/j.jmr.2023.107475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/26/2023]
Abstract
The resolution of magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra remains bounded by the spinning frequency, which is limited by the material strength of MAS rotors. Since diamond is capable of withstanding 1.5-2.5x greater MAS frequencies, compared to state-of-the art zirconia, we fabricated rotors from single crystal diamond. When combined with bearings optimized for spinning with helium gas, diamond rotors could achieve the highest MAS frequencies to date. Furthermore, the excellent microwave transmission properties and thermal conductivity of diamond could improve sensitivity enhancements in dynamic nuclear polarization (DNP) experiments. The fabrication protocol we report involves novel laser micromachining and produced rotors that presently spin at ωr/2π = 111.000 ± 0.004 kHz, with stable spinning up to 124 kHz, using N2 gas as the driving fluid. We present the first proton-detected 13C/15N MAS spectra recorded using diamond rotors, a critical step towards studying currently inaccessible ex-vivo protein samples with MAS NMR. Previously, the high aspect ratio of MAS rotors (∼10:1) precluded fabrication of MAS rotors from diamond.
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Affiliation(s)
- Natalie C Golota
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Zachary P Fredin
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Daniel P Banks
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - David Preiss
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Salima Bahri
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Prashant Patil
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - William K Langford
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Camron L Blackburn
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Erik Strand
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Brian Michael
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Blake Dastrup
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Keith A Nelson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Neil Gershenfeld
- Center for Bits and Atoms, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Robert Griffin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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5
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Quan Y, Subramanya MVH, Ouyang Y, Mardini M, Dubroca T, Hill S, Griffin RG. Coherent Dynamic Nuclear Polarization using Chirped Pulses. J Phys Chem Lett 2023; 14:4748-4753. [PMID: 37184391 DOI: 10.1021/acs.jpclett.3c00726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
This paper presents a study of coherent dynamic nuclear polarization (DNP) using frequency swept pulses at 94 GHz which optimize the polarization transfer efficiency. Accordingly, an enhancement ε ∼ 496 was observed using 10 mM trityl-OX063 as the polarizing agent in a standard 6:3:1 d8-glycerol/D2O/H2O glassing matrix at 70 K. At present, this is the largest DNP enhancement reported at this microwave frequency and temperature. Furthermore, the frequency swept pulses enhance the nuclear magnetic resonance (NMR) signal and reduce the recycle delay, accelerating the NMR signal acquisition.
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Affiliation(s)
- Yifan Quan
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Manoj V H Subramanya
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida 32310, United States
| | - Yifu Ouyang
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Michael Mardini
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Thierry Dubroca
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Stephen Hill
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida 32310, United States
| | - Robert G Griffin
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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6
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Shankar Palani R, Mardini M, Quan Y, Griffin RG. Dynamic nuclear polarization with trityl radicals. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 349:107411. [PMID: 36893654 DOI: 10.1016/j.jmr.2023.107411] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 02/17/2023] [Accepted: 02/19/2023] [Indexed: 06/18/2023]
Abstract
Despite the expanding applications of dynamic nuclear polarization (DNP) to problems in biological and materials science, there remain unresolved questions concerning DNP mechanisms. In this paper, we investigate the Zeeman DNP frequency profiles obtained with trityl radicals, OX063 and its partially deuterated analog OX071, in two commonly used glassing matrices based on glycerol and dimethyl sulfoxide (DMSO). When microwave irradiation is applied in the neighborhood of the narrow EPR transition, we observe a dispersive shape in the 1H Zeeman field and the effects are larger in DMSO than in glycerol. With the help of direct DNP observations on 13C and 2H nuclei, we investigate the origin of this dispersive field profile. In particular, we observe a weak nuclear Overhauser effect between 1H and 13C in the sample, which, when irradiating at the positive 1H solid effect (SE) condition, results in a negative enhancement of 13C spins. This observation is not consistent with thermal mixing (TM) being the mechanism responsible for the dispersive shape in the 1H DNP Zeeman frequency profile. Instead, we propose a new mechanism, resonant mixing, involving mixing of nuclear and electron spin states in a simple two-spin system without invoking electron-electron dipolar interactions.
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Affiliation(s)
- Ravi Shankar Palani
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Michael Mardini
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Yifan Quan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Robert G Griffin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
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7
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Shimon D, Cantwell KA, Joseph L, Williams EQ, Peng Z, Takahashi S, Ramanathan C. Large Room Temperature Bulk DNP of 13C via P1 Centers in Diamond. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:17777-17787. [PMID: 36304670 PMCID: PMC9589901 DOI: 10.1021/acs.jpcc.2c06145] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 09/19/2022] [Indexed: 06/16/2023]
Abstract
We use microwave-induced dynamic nuclear polarization (DNP) of the substitutional nitrogen defects (P1 centers) in diamond to hyperpolarize bulk 13C nuclei in both single crystal and powder samples at room temperature at 3.34 T. The large (>100-fold) enhancements demonstrated correspond to a greater than 10 000-fold improvement in terms of signal averaging of the 1% abundant 13C spins. The DNP was performed using low-power solid state sources under static (nonspinning) conditions. The DNP spectrum (DNP enhancement as a function of microwave frequency) of diamond powder shows features that broadly correlate with the EPR spectrum. A well-defined negative Overhauser peak and two solid effect peaks are observed for the central (m I = 0) manifold of the 14N spins. Previous low temperature measurements in diamond had measured a positive Overhauser enhancement in this manifold. Frequency-chirped millimeter-wave excitation of the electron spins is seen to significantly improve the enhancements for the two outer nuclear spin manifolds (mI = ±1) and to blur some of the sharper features associated with the central manifold. The outer lines are best fit using a combination of the cross effect and the truncated cross effect, which is known to mimic features of an Overhauser effect. Similar features are also observed in experiments on single crystal samples. The observation of all of these mechanisms in a single material system under the same experimental conditions is likely due to the significant heterogeneity of the high pressure, high temperature (HPHT) type Ib diamond samples used. Large room temperature DNP enhancements at fields above a few tesla enable spectroscopic studies with better chemical shift resolution under ambient conditions.
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Affiliation(s)
- Daphna Shimon
- Institute
of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra, Givat Ram, Jerusalem9190401, Israel
| | - Kelly A. Cantwell
- Department
of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire03755, United States
| | - Linta Joseph
- Department
of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire03755, United States
| | - Ethan Q. Williams
- Department
of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire03755, United States
| | - Zaili Peng
- Department
of Chemistry, University of Southern California, Los Angeles, California90089, United States
| | - Susumu Takahashi
- Department
of Chemistry, University of Southern California, Los Angeles, California90089, United States
- Department
of Physics and Astronomy, University of
Southern California, Los Angeles, California90089, United States
| | - Chandrasekhar Ramanathan
- Department
of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire03755, United States
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8
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Quan Y, Steiner J, Ouyang Y, Tan KO, Wenckebach WT, Hautle P, Griffin RG. Integrated, Stretched, and Adiabatic Solid Effects. J Phys Chem Lett 2022; 13:5751-5757. [PMID: 35714050 PMCID: PMC9938721 DOI: 10.1021/acs.jpclett.2c01147] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This paper presents a theory describing the dynamic nuclear polarization (DNP) process associated with an arbitrary frequency swept microwave pulse. The theory is utilized to explain the integrated solid effect (ISE) as well as the newly discovered stretched solid effect (SSE) and adiabatic solid effect (ASE). It is verified with experiments performed at 9.4 GHz (0.34 T) on single crystals of naphthalene doped with pentacene-d14. It is shown that the SSE and ASE can be more efficient than the ISE. Furthermore, the theory predicts that the efficiency of the SSE improves at high magnetic fields, where the EPR line width is small compared to the nuclear Larmor frequency. In addition, we show that the ISE, SSE, and ASE are based on similar physical principles and we suggest definitions to distinguish among them.
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Affiliation(s)
- Yifan Quan
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Jakob Steiner
- Paul Scherrer Institute (PCI), 5232 Villigen, Switzerland
| | - Yifu Ouyang
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Kong Ooi Tan
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Currently at Laboratoire des Biomolécules, LBM, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - W Thomas Wenckebach
- Paul Scherrer Institute (PCI), 5232 Villigen, Switzerland
- National High Magnetic Field Laboratory, University of Florida, Gainesville, Florida 32310, United States
| | - Patrick Hautle
- Paul Scherrer Institute (PCI), 5232 Villigen, Switzerland
| | - Robert G Griffin
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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9
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Hilty C, Kurzbach D, Frydman L. Hyperpolarized water as universal sensitivity booster in biomolecular NMR. Nat Protoc 2022; 17:1621-1657. [PMID: 35546640 DOI: 10.1038/s41596-022-00693-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 02/25/2022] [Indexed: 11/09/2022]
Abstract
NMR spectroscopy is the only method to access the structural dynamics of biomolecules at high (atomistic) resolution in their native solution state. However, this method's low sensitivity has two important consequences: (i) typically experiments have to be performed at high concentrations that increase sensitivity but are not physiological, and (ii) signals have to be accumulated over long periods, complicating the determination of interaction kinetics on the order of seconds and impeding studies of unstable systems. Both limitations are of equal, fundamental relevance: non-native conditions are of limited pharmacological relevance, and the function of proteins, enzymes and nucleic acids often relies on their interaction kinetics. To overcome these limitations, we have developed applications that involve 'hyperpolarized water' to boost signal intensities in NMR of proteins and nucleic acids. The technique includes four stages: (i) preparation of the biomolecule in partially deuterated buffers, (ii) preparation of 'hyperpolarized' water featuring enhanced 1H NMR signals via cryogenic dynamic nuclear polarization, (iii) sudden melting of the cryogenic pellet and dissolution of the protein or nucleic acid in the hyperpolarized water (enabling spontaneous exchanges of protons between water and target) and (iv) recording signal-amplified NMR spectra targeting either labile 1H or neighboring 15N/13C nuclei in the biomolecule. Water in the ensuing experiments is used as a universal 'hyperpolarization' agent, rendering the approach versatile and applicable to any biomolecule possessing labile hydrogens. Thus, questions can be addressed, ranging from protein and RNA folding problems to resolving structure-function relationships of intrinsically disordered proteins to investigating membrane interactions.
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Affiliation(s)
- Christian Hilty
- Chemistry Department, Texas A&M University, College Station, TX, USA.
| | - Dennis Kurzbach
- Faculty of Chemistry, Institute for Biological Chemistry, University of Vienna, Vienna, Austria.
| | - Lucio Frydman
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel.
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10
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Verstraete JB, Foroozandeh M. Improved design of frequency-swept pulse sequences. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 336:107146. [PMID: 35144158 DOI: 10.1016/j.jmr.2022.107146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 01/11/2022] [Accepted: 01/12/2022] [Indexed: 06/14/2023]
Abstract
Frequency-swept pulses are extensively used in magnetic resonance spectroscopic techniques for the robust manipulation of spins across wide ranges of offset frequencies in the presence of B1 field variations. Nevertheless, designing pulse sequences consisting of multiple frequency-swept pulses can be challenging, as they often require specific timings and parameter tweaking. In the present work we discuss a simple and general approach for constructing such sequences. We present new and improved pulse sequences for applications including broadband B1-tolerant CPMG (CHORUS-CPMG), broadband chirped excitation with suppression of homonuclear J-modulation (PROCHORUS), and the further compression of frequency-swept pulse sequences by superposition of pulses which reduces pulse sequence durations by 25-40%. All sequence design strategies are accompanied by mathematical presentations, experimental results, and supporting simulations.
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11
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Yang C, Ooi Tan K, Griffin RG. DNPSOUP: A simulation software package for dynamic nuclear polarization. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 334:107107. [PMID: 34894420 PMCID: PMC8819672 DOI: 10.1016/j.jmr.2021.107107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 11/04/2021] [Accepted: 11/05/2021] [Indexed: 06/01/2023]
Abstract
Dynamic Nuclear Polarization Simulation Optimized with a Unified Propagator (DNPSOUP) is an open-source numerical software program that models spin dynamics for dynamic nuclear polarization (DNP). The software package utilizes a direct numerical approach using the inhomogeneous master equation to treat the time evolution of the spin density operator under coherent Hamiltonians and stochastic relaxation effects. Here we present the details of the theory behind the software, starting from the master equation, and arriving at characteristic operators for any section of density operator time-evolution. We then provide an overview of the DNPSOUP software architecture. The efficacy of the program is demonstrated by simulating DNP field profiles on small spin systems exploiting both continuous wave and time-domain DNP mechanisms. Examples include Zeeman field profiles for the solid effect, Overhauser effect, and cross effect, and microwave field profiles for NOVEL, off-resonance NOVEL, the integrated solid effect, the stretched solid effect, and TOP-DNP. The software should facilitate a better understanding of the DNP process, aid in the design of optimized DNP polarizing agents, and allow us to examine new pulsed DNP methods at conditions that are not currently experimentally accessible, especially at high magnetic fields with high-power microwave pulses.
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Affiliation(s)
- Chen Yang
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Aspen Technology, Inc., 20 Crosby Drive, Bedford, MA 01730, United States
| | - Kong Ooi Tan
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Laboratoire des Biomolécules, LBM, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Robert G Griffin
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
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12
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Can TV, Tan KO, Yang C, Weber RT, Griffin RG. Time domain DNP at 1.2 T. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 329:107012. [PMID: 34186299 PMCID: PMC9148420 DOI: 10.1016/j.jmr.2021.107012] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/26/2021] [Accepted: 05/27/2021] [Indexed: 05/28/2023]
Abstract
We present the results of an experimental pulsed DNP study at 1.2 T (33.5 GHz/51 MHz electron and 1H Larmor frequencies, respectively). The results include a comparison of constant-amplitude NOVEL (CA-NOVEL), ramped-amplitude NOVEL (RA-NOVEL) and the frequency-swept integrated solid effect (FS-ISE) experiments all of which were performed at the NOVEL matching condition, ω1S=ω0I, where ω1S is the electron Rabi frequency andω0I the proton Larmor frequency. To the best of our knowledge, this is the first pulsed DNP study carried out at field higher than X-band (0.35 T) using the NOVEL condition. A combination of high microwave power (∼150 W) and a microwave cavity with a high Q (∼500) allowed us to satisfy the NOVEL matching condition. We also observed stretched solid effect (S2E) contributions in the Zeeman field profiles when chirped pulses are applied. Furthermore, the high quality factor of the cavity limits the concentration of the radical to ∼5 mM and generates a hysteresis in the FS-ISE experiments. Nevertheless, we observe very high DNP enhancements that are comparable to the results at X-band. These promising outcomes suggest the importance of further studies at even higher fields that delineate the instrumentation and methods required for time domain DNP.
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Affiliation(s)
- T V Can
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - K O Tan
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - C Yang
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - R T Weber
- Bruker BioSpin Corporation, Billerica, MA 01821, United States
| | - R G Griffin
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
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13
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Doty FD, Doty GN, Staab JP, Sizyuk Y, Ellis PD. New insights from broadband simulations into small overmoded smooth and corrugated terahertz waveguides and transitions for NMR-DNP. JOURNAL OF MAGNETIC RESONANCE OPEN 2021; 6-7:100009. [PMID: 34458877 PMCID: PMC8388244 DOI: 10.1016/j.jmro.2020.100009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The primary impetus for the work reported in this paper is to develop efficient overmoded waveguides (OMWGs) that employ broadband downtaper transitions that would be compatible with the severe space constraints in high-field NB magnets. Further, it is essential these would be readily manufacturable, as high precision corrugated metallic downtapers for the sub-mmw regime are very difficult to produce. We have simulated numerous alternatives to corrugated circular OMWGs, including most of the previously reported alternatives (except for many of the low-power fiberoptics options) and several novel designs. We conclude that corrugated circular metallic OMWGs are the best of the reported options to date (except from a cost perspective) for diameters down to ~1.5λ, but the corrugation parameters for small OMWGs need to be significantly different from the previously published guidelines that have worked well for large OMWGs. With numerically optimized small OMWGs, easily manufacturable smooth downtapers appear to work as well as corrugated downtapers in many cases relevant to MAS-DNP probes. Our example simulations will be for the 170-230 GHz range, but the lessons and results should be readily applicable to other ranges by simple scaling.
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14
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Miyanishi K, Segawa T, Takeda K, Ohki I, Onoda S, Ohshima T, Abe H, Takashima H, Takeuchi S, Shames A, Morita K, Wang Y, So FK, Terada D, Igarashi R, Kagawa A, Kitagawa M, Mizuochi N, Shirakawa M, Negoro M. Room-temperature hyperpolarization of polycrystalline samples with optically polarized triplet electrons: pentacene or nitrogen-vacancy center in diamond? MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2021; 2:33-48. [PMID: 37904782 PMCID: PMC10539752 DOI: 10.5194/mr-2-33-2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 01/25/2021] [Indexed: 11/01/2023]
Abstract
We demonstrate room-temperature 13 C hyperpolarization by dynamic nuclear polarization (DNP) using optically polarized triplet electron spins in two polycrystalline systems: pentacene-doped [carboxyl-13 C] benzoic acid and microdiamonds containing nitrogen-vacancy (NV- ) centers. For both samples, the integrated solid effect (ISE) is used to polarize the 13 C spin system in magnetic fields of 350-400 mT. In the benzoic acid sample, the 13 C spin polarization is enhanced by up to 0.12 % through direct electron-to-13 C polarization transfer without performing dynamic 1 H polarization followed by 1 H - 13 C cross-polarization. In addition, the ISE has been successfully applied to polarize naturally abundant 13 C spins in a microdiamond sample to 0.01 %. To characterize the buildup of the 13 C polarization, we discuss the efficiencies of direct polarization transfer between the electron and 13 C spins as well as that of 13 C - 13 C spin diffusion, examining various parameters which are beneficial or detrimental for successful bulk dynamic 13 C polarization.
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Affiliation(s)
- Koichiro Miyanishi
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Takuya F. Segawa
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-Ku, Kyoto 615-8510, Japan
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Kazuyuki Takeda
- Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Izuru Ohki
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Shinobu Onoda
- Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
- Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
| | - Takeshi Ohshima
- Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
- Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
| | - Hiroshi Abe
- Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
- Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
| | - Hideaki Takashima
- Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Shigeki Takeuchi
- Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Alexander I. Shames
- Department of Physics, Ben-Gurion University of the Negev, 8410501 Beer-Sheva, Israel
| | - Kohki Morita
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Yu Wang
- Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Frederick T.-K. So
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-Ku, Kyoto 615-8510, Japan
- Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
| | - Daiki Terada
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-Ku, Kyoto 615-8510, Japan
- Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
| | - Ryuji Igarashi
- Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
- Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
- JST, PRESTO, Kawaguchi, Japan
| | - Akinori Kagawa
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
- JST, PRESTO, Kawaguchi, Japan
- Center for Quantum Information and Quantum Biology, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, 1-2 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Masahiro Kitagawa
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
- Center for Quantum Information and Quantum Biology, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, 1-2 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Norikazu Mizuochi
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Masahiro Shirakawa
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-Ku, Kyoto 615-8510, Japan
- Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
| | - Makoto Negoro
- Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
- JST, PRESTO, Kawaguchi, Japan
- Center for Quantum Information and Quantum Biology, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, 1-2 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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15
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Gizatullin B, Mattea C, Stapf S. Field-cycling NMR and DNP - A friendship with benefits. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 322:106851. [PMID: 33423755 DOI: 10.1016/j.jmr.2020.106851] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 10/09/2020] [Accepted: 10/11/2020] [Indexed: 06/12/2023]
Abstract
Field-cycling relaxometry, or rather its electronic version with a resistive magnet which requires signal detection at a field strength of 1 Tesla or below, remains an inherently insensitive technique due to the construction compromise that goes along with the need for a fast-switching, low-inductance magnet. For the same reasons, signal lifetime is short and frequency resolution is typically not given, at least for the predominantly used hydrogen nuclei. Dynamic Nuclear Polarization (DNP) bears the potential to circumvent these disadvantages: not only has it been demonstrated to enhance magnetization by up to three orders of magnitude beyond its thermal value, but it also provides the possibility to address particular parts of a molecule, thus generating selectivity even in the absence of spectral resolution. At the same time, DNP requires the introduction of stable radicals giving rise to additional relaxation contributions. This article presents a straightforward way to recover the native relaxation rates of the undisturbed system, and shows examples in different research fields where field-cycling relaxometry is traditionally used for refining models of molecular dynamics and interactions.
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Affiliation(s)
- Bulat Gizatullin
- FG Technische Physik II/Polymerphysik, Technische Universität Ilmenau, D-98684 Ilmenau, Germany
| | - Carlos Mattea
- FG Technische Physik II/Polymerphysik, Technische Universität Ilmenau, D-98684 Ilmenau, Germany
| | - Siegfried Stapf
- FG Technische Physik II/Polymerphysik, Technische Universität Ilmenau, D-98684 Ilmenau, Germany.
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16
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Foroozandeh M. Spin dynamics during chirped pulses: applications to homonuclear decoupling and broadband excitation. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 318:106768. [PMID: 32917298 DOI: 10.1016/j.jmr.2020.106768] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 05/27/2020] [Accepted: 06/02/2020] [Indexed: 06/11/2023]
Abstract
Swept-frequency pulses have found applications in a wide range of areas including spectroscopic techniques where efficient control of spins is required. For many of these applications, a good understanding of the evolution of spin systems during these pulses plays a vital role, not only in describing the mechanism of techniques, but also in enabling new methodologies. In magnetic resonance spectroscopy, broadband inversion, refocusing, and excitation using these pulses are among the most used applications in NMR, ESR, MRI, and in vivo MRS. In the present survey, a general expression for chirped pulses will be introduced, and some numerical approaches to calculate the spin dynamics during chirped pulses via solutions of the well-known Liouville-von Neumann equation and the lesser-explored Wei-Norman Lie algebra along with comprehensive examples are presented. In both cases, spin state trajectories are calculated using the solution of differential equations. Additionally, applications of the proposed methods to study the spin dynamics during the PSYCHE pulse element for broadband homonuclear decoupling and the CHORUS sequence for broadband excitation will be presented.
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17
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Abstract
The solid effect (SE) is a two spin dynamic nuclear polarization (DNP) mechanism that enhances the sensitivity in NMR experiments by irradiation of the electron-nuclear spin transitions with continuous wave (CW) microwaves at ω0S ± ω0I, where ω0S and ω0I are electron and nuclear Larmor frequencies, respectively. Using trityl (OX063), dispersed in a 60/40 glycerol/water mixture at 80 K, as a polarizing agent, we show here that application of a chirped microwave pulse, with a bandwidth comparable to the EPR line width applied at the SE matching condition, improves the enhancement by a factor of 2.4 over the CW method. Furthermore, the chirped pulse yields an enhancement that is ∼20% larger than obtained with the ramped-amplitude NOVEL (RA-NOVEL), which to date has achieved the largest enhancements in time domain DNP experiments. Numerical simulations suggest that the spins follow an adiabatic trajectory during the polarization transfer; hence, we denote this sequence as an adiabatic solid effect (ASE). We foresee that ASE will be a practical pulsed DNP experiment to be implemented at higher static magnetic fields due to the moderate power requirement. In particular, the ASE uses only 13% of the maximum microwave power required for RA-NOVEL.
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Affiliation(s)
- Kong Ooi Tan
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Ralph T Weber
- Bruker BioSpin Corporation, Billerica, Massachusetts 01821, United States
| | - Thach V Can
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Robert G Griffin
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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18
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Abstract
Dynamic nuclear polarization (DNP) is one of the most prominent methods of sensitivity enhancement in nuclear magnetic resonance (NMR). Even though solid-state DNP under magic-angle spinning (MAS) has left the proof-of-concept phase and has become an important tool for structural investigations of biomolecules as well as materials, it is still far from mainstream applicability because of the potentially overwhelming combination of unique instrumentation, complex sample preparation, and a multitude of different mechanisms and methods available. In this review, I introduce the diverse field and history of DNP, combining aspects of NMR and electron paramagnetic resonance. I then explain the general concepts and detailed mechanisms relevant at high magnetic field, including solution-state methods based on Overhauser DNP but with a greater focus on the more established MAS DNP methods. Finally, I review practical considerations and fields of application and discuss future developments.
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Affiliation(s)
- Björn Corzilius
- Institute of Chemistry and Department of Life, Light and Matter, University of Rostock, 18059 Rostock, Germany;
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19
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Kaminker I. Recent Advances in Magic Angle Spinning‐Dynamic Nuclear Polarization Methodology. Isr J Chem 2019. [DOI: 10.1002/ijch.201900092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Ilia Kaminker
- School of ChemistryTel Aviv University Ramat Aviv 6997801 Tel Aviv Israel
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20
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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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21
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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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22
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Rankin AGM, Trébosc J, Pourpoint F, Amoureux JP, Lafon O. Recent developments in MAS DNP-NMR of materials. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 101:116-143. [PMID: 31189121 DOI: 10.1016/j.ssnmr.2019.05.009] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 05/21/2019] [Accepted: 05/21/2019] [Indexed: 05/03/2023]
Abstract
Solid-state NMR spectroscopy is a powerful technique for the characterization of the atomic-level structure and dynamics of materials. Nevertheless, the use of this technique is often limited by its lack of sensitivity, which can prevent the observation of surfaces, defects or insensitive isotopes. Dynamic Nuclear Polarization (DNP) has been shown to improve by one to three orders of magnitude the sensitivity of NMR experiments on materials under Magic-Angle Spinning (MAS), at static magnetic field B0 ≥ 5 T, conditions allowing for the acquisition of high-resolution spectra. The field of DNP-NMR spectroscopy of materials has undergone a rapid development in the last ten years, spurred notably by the availability of commercial DNP-NMR systems. We provide here an in-depth overview of MAS DNP-NMR studies of materials at high B0 field. After a historical perspective of DNP of materials, we describe the DNP transfers under MAS, the transport of polarization by spin diffusion and the various contributions to the overall sensitivity of DNP-NMR experiments. We discuss the design of tailored polarizing agents and the sample preparation in the case of materials. We present the DNP-NMR hardware and the influence of key experimental parameters, such as microwave power, magnetic field, temperature and MAS frequency. We give an overview of the isotopes that have been detected by this technique, and the NMR methods that have been combined with DNP. Finally, we show how MAS DNP-NMR has been applied to gain new insights into the structure of organic, hybrid and inorganic materials with applications in fields, such as health, energy, catalysis, optoelectronics etc.
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Affiliation(s)
- Andrew G M Rankin
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181, UCCS, Unité de Catalyse et Chimie du Solide, F-59000, Lille, France
| | - Julien Trébosc
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181, UCCS, Unité de Catalyse et Chimie du Solide, F-59000, Lille, France; Univ. Lille, CNRS-FR2638, Fédération Chevreul, F-59000 Lille, France
| | - Frédérique Pourpoint
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181, UCCS, Unité de Catalyse et Chimie du Solide, F-59000, Lille, France
| | - Jean-Paul Amoureux
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181, UCCS, Unité de Catalyse et Chimie du Solide, F-59000, Lille, France; Bruker Biospin, 34 rue de l'industrie, F-67166, Wissembourg, France
| | - Olivier Lafon
- Univ. Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181, UCCS, Unité de Catalyse et Chimie du Solide, F-59000, Lille, France; Institut Universitaire de France, 1 rue Descartes, F-75231, Paris, France.
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23
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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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24
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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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25
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Purea A, Reiter C, Dimitriadis AI, de Rijk E, Aussenac F, Sergeyev I, Rosay M, Engelke F. Improved waveguide coupling for 1.3 mm MAS DNP probes at 263 GHz. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 302:43-49. [PMID: 30953925 DOI: 10.1016/j.jmr.2019.03.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 03/26/2019] [Accepted: 03/27/2019] [Indexed: 06/09/2023]
Abstract
We consider the geometry of a radially irradiated microwave beam in MAS DNP NMR probes and its impact on DNP enhancement. Two related characteristic features are found to be relevant: (i) the focus of the microwave beam on the DNP MAS sample and (ii) the microwave magnetic field magnitude in the sample. We present a waveguide coupler setup that enables us to significantly improve beam focus and field magnitude in 1.3 mm MAS DNP probes at a microwave frequency of 263 GHz, which results in an increase of the DNP enhancement by a factor of 2 compared to previous standard hardware setups. We discuss the implications of improved coupling and its potential to enable cutting-edge applications, such as pulsed high-field DNP and the use of low-power solid-state microwave sources.
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26
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Tan KO, Yang C, Weber RT, Mathies G, Griffin RG. Time-optimized pulsed dynamic nuclear polarization. SCIENCE ADVANCES 2019; 5:eaav6909. [PMID: 30746482 PMCID: PMC6357739 DOI: 10.1126/sciadv.aav6909] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 12/05/2018] [Indexed: 05/05/2023]
Abstract
Pulsed dynamic nuclear polarization (DNP) techniques can accomplish electron-nuclear polarization transfer efficiently with an enhancement factor that is independent of the Zeeman field. However, they often require large Rabi frequencies and, therefore, high-power microwave irradiation. Here, we propose a new low-power DNP sequence for static samples that is composed of a train of microwave pulses of length τp spaced with delays d. A particularly robust DNP condition using a period τm = τp + d set to ~1.25 times the Larmor period τLarmor is investigated which is a time-optimized pulsed DNP sequence (TOP-DNP). At 0.35 T, we obtained an enhancement of ~200 using TOP-DNP compared to ~172 with nuclear spin orientation via electron spin locking (NOVEL), a commonly used pulsed DNP sequence, while using only ~7% microwave power required for NOVEL. Experimental data and simulations at higher fields suggest a field-independent enhancement factor, as predicted by the effective Hamiltonian.
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Affiliation(s)
- Kong Ooi Tan
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Chen Yang
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | - Guinevere Mathies
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Robert G. Griffin
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Corresponding author.
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Leavesley A, Jain S, Kamniker I, Zhang H, Rajca S, Rajca A, Han S. Maximizing NMR signal per unit time by facilitating the e-e-n cross effect DNP rate. Phys Chem Chem Phys 2018; 20:27646-27657. [PMID: 30375593 DOI: 10.1039/c8cp04909b] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The dynamic nuclear polarization (DNP) efficiency is critically dependent on the properties of the radical, solvent, and solute constituting the sample system. In this study, we focused on the three spin e-e-n cross effect (CE)'s influence on the nuclear longitudinal relaxation time constant T1n, the build-up time constants of nuclear magnetic resonance (NMR) signal, TDNP and DNP-enhancement of NMR signal. The dipolar interaction strength between the electron spins driving the e-e-n process was systematically modulated using mono-, di-, tri-, and dendritic-nitroxide radicals, while maintaining a constant global electron spin concentration of 10 mM. Experimental results showed that an increase in electron spin clustering led to an increased electron spin depolarization, as mapped by electron double resonance (ELDOR), and a dramatically shortened T1n and TDNP time constants under static and magic angle spinning (MAS) conditions. A theoretical analysis reveals that strong e-e interactions, caused by electron spin clustering, increase the CE rate. The three spin e-e-n CE is a hitherto little recognized mechanism for shortening T1n and TDNP in solid-state NMR experiments at cryogenic temperatures, and offers a design principle to enhance the effective CE DNP enhancement per unit time. Fast CE rates will benefit DNP at liquid helium temperatures, or at higher magnetic fields and pulsed DNP, where slow e-e-n polarization transfer rate is a key bottleneck to achieving maximal DNP performance.
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Affiliation(s)
- Alisa Leavesley
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
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