1
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Nevzorov AA, Marek A, Milikisiyants S, Smirnov AI. High-frequency high-power DNP/EPR spectrometer operating at 7 T magnetic field. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 362:107677. [PMID: 38631171 PMCID: PMC11102838 DOI: 10.1016/j.jmr.2024.107677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 03/26/2024] [Accepted: 04/09/2024] [Indexed: 04/19/2024]
Abstract
One of the most essential prerequisites for the development of pulse Dynamic Nuclear Polarization (DNP) is the ability to generate high-power coherent mm-wave pulses at the electron precession frequencies corresponding to the magnetic fields of modern high-resolution NMR spectrometers. As a major step towards achieving this goal, an Extended Interaction Klystron (EIK) pulse amplifier custom-built by the Communications and Power Industries, Inc. and producing up to 140 W at 197.8 GHz, was integrated with in-house built NMR/DNP/EPR spectrometer operating at 7 T magnetic field. The spectrometer employs a Thomas Keating, Ltd. quasioptical bridge to direct mm-waves into a homebuilt DNP probe incorporating photonic bandgap (PBG) resonators to further boost electronic B1e fields. Three-pulse electron spin echo nutation experiments were employed to characterize the B1e fields at the sample by operating the homodyne 198 GHz bridge in an induction mode. Room-temperature experiments with a single-crystal high-pressure, high-temperature (HPHT) diamond and a polystyrene film doped with BDPA radical yielded < 9 ns π/2 pulses at ca. 50 W specified EIK output at the corresponding resonance frequencies and the PBG resonator quality factor of Q≈300. DNP experiments carried out in a "gated" mode by supplying 20 μs mm-wave pulses every 1 ms yielded 13C solid-effect DNP with gains up to 20 for the polystyrene-BDPA sample at natural 13C abundance. For a single-crystal HPHT diamond, the gated DNP mode yielded almost the same 13C enhancement as a low-power continuous wave (CW) mode at 0.4 W, whereas no DNP effect was observed for the BDPA/polystyrene sample in the latter case. To illustrate the versatility of our upgraded DNP spectrometer, room-temperature Overhauser DNP enhancements of 7-14 for 31P NMR signal were demonstrated using a liquid droplet of 1 M tri-phenyl phosphine co-dissolved with 100 mM of BDPA in toluene‑d8.
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Affiliation(s)
- Alexander A Nevzorov
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Dr., Raleigh, NC 27695, US.
| | - Antonin Marek
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Dr., Raleigh, NC 27695, US
| | - Sergey Milikisiyants
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Dr., Raleigh, NC 27695, US
| | - Alex I Smirnov
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Dr., Raleigh, NC 27695, US.
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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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Paul S, Bouleau E, Reynard-Feytis Q, Arnaud JP, Bancel F, Rollet B, Dalban-Moreynas P, Reiter C, Purea A, Engelke F, Hediger S, De Paëpe G. Sustainable and cost-effective MAS DNP-NMR at 30 K with cryogenic sample exchange. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 356:107561. [PMID: 37837749 DOI: 10.1016/j.jmr.2023.107561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 09/18/2023] [Accepted: 09/22/2023] [Indexed: 10/16/2023]
Abstract
We report here instrumental developments to achieve sustainable, cost-effective cryogenic Helium sample spinning in order to conduct dynamic nuclear polarisation (DNP) and solid-state NMR (ssNMR) at ultra-low temperatures (<30 K). More specifically, we describe an efficient closed-loop helium system composed of a powerful heat exchanger (95% efficient), a single cryocooler, and a single helium compressor to power the sample spinning and cooling. The system is integrated with a newly designed triple-channel NMR probe that minimizes thermal losses without compromising the radio frequency (RF) performance and spinning stability (±0.05%). The probe is equipped with an innovative cryogenic sample exchange system that allows swapping samples in minutes without introducing impurities in the closeloop system. We report that significant gain in sensitivity can be obtained at 30-40 K on large micro-crystalline molecules with unfavorable relaxation timescales, making them difficult or impossible to polarize at 100 K. We also report rotor-synchronized 2D experiments to demonstrate the stability of the system.
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Affiliation(s)
- Subhradip Paul
- Univ. Grenoble. Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France
| | - Eric Bouleau
- Univ. Grenoble Alpes, CEA, IRIG, DSBT, 38000 Grenoble, France
| | | | | | - Florian Bancel
- Univ. Grenoble Alpes, CEA, IRIG, DSBT, 38000 Grenoble, France
| | - Bertrand Rollet
- Univ. Grenoble Alpes, CEA, IRIG, DSBT, 38000 Grenoble, France
| | | | | | | | | | - Sabine Hediger
- Univ. Grenoble. Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France
| | - Gaël De Paëpe
- Univ. Grenoble. Alpes, CEA, CNRS, IRIG, MEM, 38000 Grenoble, France.
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4
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Price LE, Alaniva N, Millen M, Epprecht T, Urban M, Däpp A, Barnes AB. Cryogenic-compatible spherical rotors and stators for magic angle spinning dynamic nuclear polarization. MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2023; 4:231-241. [PMID: 37904856 PMCID: PMC10539783 DOI: 10.5194/mr-4-231-2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 06/21/2023] [Indexed: 11/01/2023]
Abstract
Cryogenic magic angle spinning (MAS) is a standard technique utilized for dynamic nuclear polarization (DNP) in solid-state nuclear magnetic resonance (NMR). Here we describe the optimization and implementation of a stator for cryogenic MAS with 9.5 mm diameter spherical rotors, allowing for DNP experiments on large sample volumes. Designs of the stator and rotor for cryogenic MAS build on recent advancements of MAS spheres and take a step further to incorporate sample insert and eject and a temperature-independent spinning stability of ± 1 Hz. At a field of 7 T and spinning at 2.0 kHz with a sample temperature of 105-107 K, DNP enhancements of 256 and 200 were observed for 124 and 223 µ L sample volumes, respectively, each consisting of 4 M 13 C, 15 N-labeled urea and 20 mM AMUPol in a glycerol-water glassy matrix.
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Affiliation(s)
- Lauren E. Price
- Department of Chemistry and Applied Biochemistry, ETH Zürich,
Zurich 8093, Switzerland
| | - Nicholas Alaniva
- Department of Chemistry and Applied Biochemistry, ETH Zürich,
Zurich 8093, Switzerland
| | - Marthe Millen
- Department of Chemistry and Applied Biochemistry, ETH Zürich,
Zurich 8093, Switzerland
| | - Till Epprecht
- Department of Chemistry and Applied Biochemistry, ETH Zürich,
Zurich 8093, Switzerland
| | - Michael Urban
- Department of Chemistry and Applied Biochemistry, ETH Zürich,
Zurich 8093, Switzerland
| | - Alexander Däpp
- Department of Chemistry and Applied Biochemistry, ETH Zürich,
Zurich 8093, Switzerland
| | - Alexander B. Barnes
- Department of Chemistry and Applied Biochemistry, ETH Zürich,
Zurich 8093, Switzerland
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5
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Endeward B, Bretschneider M, Trenkler P, Prisner TF. Implementation and applications of shaped pulses in EPR. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2023; 136-137:61-82. [PMID: 37716755 DOI: 10.1016/j.pnmrs.2023.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 04/12/2023] [Accepted: 04/26/2023] [Indexed: 09/18/2023]
Abstract
In this review, we describe the application of shaped pulses for EPR spectroscopy. Pulses generated by fast arbitrary waveform generators are mostly used in the field of EPR spectroscopy for broadband (200 MHz-1 GHz) excitation of paramagnetic species. The implementation and optimization of such broadband pulses in existing EPR spectrometers, often designed and optimized for short rectangular microwave pulses, is demanding. Therefore, a major part of this review will describe in detail the implementation, testing and optimization of shaped pulses in existing EPR spectrometers. Additionally, we review applications using such pulses for broadband inversion of longitudinal magnetization as well as for the creation and manipulation of transverse magnetization in the field of dipolar and hyperfine EPR spectroscopy. They demonstrate the great potential of shaped pulses to improve the performance of pulsed EPR experiments. We give a brief theoretical description of shaped pulses and their limitations, especially for adiabatic pulses, most often used in EPR. We believe that this review can on the one hand be of practical use to EPR groups starting to work with such pulses, and on the other hand give readers an overview of the state of the art of shaped pulse applications in EPR spectroscopy.
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Affiliation(s)
- Burkhard Endeward
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue Str. 7, 60438 Frankfurt am Main, Germany
| | - Matthias Bretschneider
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue Str. 7, 60438 Frankfurt am Main, Germany
| | - Paul Trenkler
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue Str. 7, 60438 Frankfurt am Main, Germany
| | - Thomas F Prisner
- Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max-von-Laue Str. 7, 60438 Frankfurt am Main, Germany.
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6
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Mardini M, Palani RS, Ahmad IM, Mandal S, Jawla SK, Bryerton E, Temkin RJ, Sigurdsson ST, Griffin RG. Frequency-swept dynamic nuclear polarization. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 353:107511. [PMID: 37385067 DOI: 10.1016/j.jmr.2023.107511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/14/2023] [Accepted: 06/15/2023] [Indexed: 07/01/2023]
Abstract
Dynamic nuclear polarization (DNP) improves the sensitivity of NMR spectroscopy by the transfer of electron polarization to nuclei via irradiation of electron-nuclear transitions with microwaves at the appropriate frequency. For fields > 5 T and using g ∼ 2 electrons as polarizing agents, this requires the availability of microwave sources operating at >140 GHz. Therefore, microwave sources for DNP have generally been continuous-wave (CW) gyrotrons, and more recently solid state, oscillators operating at a fixed frequency and power. This constraint has limited the DNP mechanisms which can be exploited, and stymied the development of new time domain mechanisms. We report here the incorporation of a microwave source enabling facile modulation of frequency, amplitude, and phase at 9 T (250 GHz microwave frequency), and we have used the source for magic-angle spinning (MAS) NMR experiments. The experiments include investigations of CW DNP mechanisms, the advantage of frequency-chirped irradiation, and a demonstration of an Overhauser enhancement of ∼25 with a recently reported water-soluble BDPA radical, highlighting the potential for affordable and compact microwave sources to achieve significant enhancement in aqueous samples, including biological macromolecules. With the development of suitable microwave amplifiers, it should permit exploration of multiple new avenues involving time domain experiments.
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Affiliation(s)
- Michael Mardini
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Ravi Shankar Palani
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Iram M Ahmad
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Sucharita Mandal
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Sudheer K Jawla
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Eric Bryerton
- Virginia Diodes Corporation, Charlottesville, VA 22902, United States
| | - Richard J Temkin
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Snorri Th Sigurdsson
- Department of Chemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Robert G Griffin
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
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7
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Menzildjian G, Schlagnitweit J, Casano G, Ouari O, Gajan D, Lesage A. Polarizing agents for efficient high field DNP solid-state NMR spectroscopy under magic-angle spinning: from design principles to formulation strategies. Chem Sci 2023; 14:6120-6148. [PMID: 37325158 PMCID: PMC10266460 DOI: 10.1039/d3sc01079a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/09/2023] [Indexed: 06/17/2023] Open
Abstract
Dynamic Nuclear Polarization (DNP) has recently emerged as a cornerstone approach to enhance the sensitivity of solid-state NMR spectroscopy under Magic Angle Spinning (MAS), opening unprecedented analytical opportunities in chemistry and biology. DNP relies on a polarization transfer from unpaired electrons (present in endogenous or exogenous polarizing agents) to nearby nuclei. Developing and designing new polarizing sources for DNP solid-state NMR spectroscopy is currently an extremely active research field per se, that has recently led to significant breakthroughs and key achievements, in particular at high magnetic fields. This review describes recent developments in this area, highlighting key design principles that have been established over time and led to the introduction of increasingly more efficient polarizing sources. After a short introduction, Section 2 presents a brief history of solid-state DNP, highlighting the main polarization transfer schemes. The third section is devoted to the development of dinitroxide radicals, discussing the guidelines that were progressively established to design the fine-tuned molecular structures in use today. In Section 4, we describe recent efforts in developing hybrid radicals composed of a narrow EPR line radical covalently linked to a nitroxide, highlighting the parameters that modulate the DNP efficiency of these mixed structures. Section 5 reviews recent advances in the design of metal complexes suitable for DNP MAS NMR as exogenous electron sources. In parallel, current strategies that exploit metal ions as endogenous polarization sources are discussed. Section 6 briefly describes the recent introduction of mixed-valence radicals. In the last part, experimental aspects regarding sample formulation are reviewed to make best use of these polarizing agents in a broad panel of application fields.
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Affiliation(s)
- Georges Menzildjian
- Centre de RMN à, Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) 5 Rue de la doua 69100 Villeurbanne France
| | - Judith Schlagnitweit
- Centre de RMN à, Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) 5 Rue de la doua 69100 Villeurbanne France
| | - Gilles Casano
- Aix Marseille Univ., CNRS, Institut de Chimie Radicalaire, UMR 7273 Marseille France
| | - Olivier Ouari
- Aix Marseille Univ., CNRS, Institut de Chimie Radicalaire, UMR 7273 Marseille France
| | - David Gajan
- Centre de RMN à, Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) 5 Rue de la doua 69100 Villeurbanne France
| | - Anne Lesage
- Centre de RMN à, Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) 5 Rue de la doua 69100 Villeurbanne France
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8
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Armstrong CM, Snively EC, Shumail M, Nantista C, Li Z, Tantawi S, Loo BW, Temkin RJ, Griffin RG, Feng J, Dionisio R, Mentgen F, Ayllon N, Henderson MA, Goodman TP. Frontiers in the Application of RF Vacuum Electronics. IEEE TRANSACTIONS ON ELECTRON DEVICES 2023; 70:2643-2655. [PMID: 37250956 PMCID: PMC10216895 DOI: 10.1109/ted.2023.3239841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The application of radio frequency (RF) vacuum electronics for the betterment of the human condition began soon after the invention of the first vacuum tubes in the 1920s and has not stopped since. Today, microwave vacuum devices are powering important applications in health treatment, material and biological science, wireless communication-terrestrial and space, Earth environment remote sensing, and the promise of safe, reliable, and inexhaustible energy. This article highlights some of the exciting application frontiers of vacuum electronics.
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Affiliation(s)
| | - Emma C Snively
- SLAC National Accelerator Laboratory, Menlo Park, CA 94025 USA
| | | | | | - Zenghai Li
- SLAC National Accelerator Laboratory, Menlo Park, CA 94025 USA
| | - Sami Tantawi
- SLAC National Accelerator Laboratory, Menlo Park, CA 94025 USA
| | - Bill W Loo
- Department of Radiation Oncology and Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA 94305 USA
| | - Richard J Temkin
- Department of Physics and the Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Robert G Griffin
- Department of Chemistry and the Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Jinjun Feng
- Beijing Vacuum Electronics Research Institute, Beijing 100015, China
| | - Roberto Dionisio
- RF Equipment and Technologies Section, European Space Agency (ESA), NL-2200 AG Noordwijk, The Netherlands
| | - Felix Mentgen
- RF Equipment and Technologies Section, European Space Agency (ESA), NL-2200 AG Noordwijk, The Netherlands
| | - Natanael Ayllon
- RF Equipment and Technologies Section, European Space Agency (ESA), NL-2200 AG Noordwijk, The Netherlands
| | - Mark A Henderson
- United Kingdom Atomic Energy Authority, Culham Science Centre, OX14 3DB Abingdon, U.K
| | - Timothy P Goodman
- Swiss Plasma Center, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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9
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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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10
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Tagami K, Thicklin R, Jain S, Equbal A, Li M, Zens T, Siaw A, Han S. Design of a cryogen-free high field dual EPR and DNP probe. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 347:107351. [PMID: 36599253 DOI: 10.1016/j.jmr.2022.107351] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 11/29/2022] [Accepted: 11/30/2022] [Indexed: 06/17/2023]
Abstract
We present the design and construction of a cryogen free, dual electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) probe for novel dynamic nuclear polarization (DNP) experiments and concurrent "in situ" analysis of DNP mechanisms. We focus on the probe design that meets the balance between EPR, NMR, and low temperature performance, while maintaining a high degree of versatility: allowing multi-nuclear NMR detection as well as broadband DNP/EPR excitation/detection. To accomplish high NMR/EPR performance, we implement a novel inductively coupled double resonance NMR circuit (1H-13C) in a solid state probe operating at cryogenic temperatures. The components of the circuit were custom built to provide maximum NMR performance, and the physical layout of this circuit was numerically optimized via magnetic field simulations to allow maximum microwave transmission to the sample for optimal EPR performance. Furthermore this probe is based around a cryogen free gas exchange cryostat and has been designed to allow unlimited experiment times down to 8.5 Kelvin with minimal cost. The affordability of EPR/DNP experiment is an extremely important aspect for broader impact with magnetic resonance measurements. The purpose of this article is to provide as complete information as we have available for others with interest in building a dual DNP/EPR instrument based around a cryogen-free cryostat.
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Affiliation(s)
- Kan Tagami
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Raymond Thicklin
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Sheetal Jain
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Asif Equbal
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Miranda Li
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Toby Zens
- JEOL USA, Inc., 11 Dearborn Road, Peabody, MA 01960, United States
| | - Anthony Siaw
- JEOL USA, Inc., 11 Dearborn Road, Peabody, MA 01960, United States
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, United States.
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11
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Eills J, Budker D, Cavagnero S, Chekmenev EY, Elliott SJ, Jannin S, Lesage A, Matysik J, Meersmann T, Prisner T, Reimer JA, Yang H, Koptyug IV. Spin Hyperpolarization in Modern Magnetic Resonance. Chem Rev 2023; 123:1417-1551. [PMID: 36701528 PMCID: PMC9951229 DOI: 10.1021/acs.chemrev.2c00534] [Citation(s) in RCA: 45] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Magnetic resonance techniques are successfully utilized in a broad range of scientific disciplines and in various practical applications, with medical magnetic resonance imaging being the most widely known example. Currently, both fundamental and applied magnetic resonance are enjoying a major boost owing to the rapidly developing field of spin hyperpolarization. Hyperpolarization techniques are able to enhance signal intensities in magnetic resonance by several orders of magnitude, and thus to largely overcome its major disadvantage of relatively low sensitivity. This provides new impetus for existing applications of magnetic resonance and opens the gates to exciting new possibilities. In this review, we provide a unified picture of the many methods and techniques that fall under the umbrella term "hyperpolarization" but are currently seldom perceived as integral parts of the same field. Specifically, before delving into the individual techniques, we provide a detailed analysis of the underlying principles of spin hyperpolarization. We attempt to uncover and classify the origins of hyperpolarization, to establish its sources and the specific mechanisms that enable the flow of polarization from a source to the target spins. We then give a more detailed analysis of individual hyperpolarization techniques: the mechanisms by which they work, fundamental and technical requirements, characteristic applications, unresolved issues, and possible future directions. We are seeing a continuous growth of activity in the field of spin hyperpolarization, and we expect the field to flourish as new and improved hyperpolarization techniques are implemented. Some key areas for development are in prolonging polarization lifetimes, making hyperpolarization techniques more generally applicable to chemical/biological systems, reducing the technical and equipment requirements, and creating more efficient excitation and detection schemes. We hope this review will facilitate the sharing of knowledge between subfields within the broad topic of hyperpolarization, to help overcome existing challenges in magnetic resonance and enable novel applications.
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Affiliation(s)
- James Eills
- Institute
for Bioengineering of Catalonia, Barcelona
Institute of Science and Technology, 08028Barcelona, Spain,
| | - Dmitry Budker
- Johannes
Gutenberg-Universität Mainz, 55128Mainz, Germany,Helmholtz-Institut,
GSI Helmholtzzentrum für Schwerionenforschung, 55128Mainz, Germany,Department
of Physics, UC Berkeley, Berkeley, California94720, United States
| | - Silvia Cavagnero
- Department
of Chemistry, University of Wisconsin, Madison, Madison, Wisconsin53706, United States
| | - Eduard Y. Chekmenev
- Department
of Chemistry, Integrative Biosciences (IBio), Karmanos Cancer Institute
(KCI), Wayne State University, Detroit, Michigan48202, United States,Russian
Academy of Sciences, Moscow119991, Russia
| | - Stuart J. Elliott
- Molecular
Sciences Research Hub, Imperial College
London, LondonW12 0BZ, United Kingdom
| | - Sami Jannin
- Centre
de RMN à Hauts Champs de Lyon, Université
de Lyon, CNRS, ENS Lyon, Université Lyon 1, 69100Villeurbanne, France
| | - Anne Lesage
- Centre
de RMN à Hauts Champs de Lyon, Université
de Lyon, CNRS, ENS Lyon, Université Lyon 1, 69100Villeurbanne, France
| | - Jörg Matysik
- Institut
für Analytische Chemie, Universität
Leipzig, Linnéstr. 3, 04103Leipzig, Germany
| | - Thomas Meersmann
- Sir
Peter Mansfield Imaging Centre, University Park, School of Medicine, University of Nottingham, NottinghamNG7 2RD, United Kingdom
| | - Thomas Prisner
- Institute
of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic
Resonance, Goethe University Frankfurt, , 60438Frankfurt
am Main, Germany
| | - Jeffrey A. Reimer
- Department
of Chemical and Biomolecular Engineering, UC Berkeley, and Materials Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California94720, United States
| | - Hanming Yang
- Department
of Chemistry, University of Wisconsin, Madison, Madison, Wisconsin53706, United States
| | - Igor V. Koptyug
- International Tomography Center, Siberian
Branch of the Russian Academy
of Sciences, 630090Novosibirsk, Russia,
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12
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Tan KO, Yang L, Mardini M, Cheong CB, Driesschaert B, Dincă M, Griffin RG. Observing Nearby Nuclei on Paramagnetic Trityls and MOFs via DNP and Electron Decoupling. Chemistry 2022; 28:e202202556. [PMID: 36089532 PMCID: PMC9795816 DOI: 10.1002/chem.202202556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Indexed: 12/30/2022]
Abstract
Dynamic nuclear polarization (DNP) is an NMR sensitivity enhancement technique that mediates polarization transfer from unpaired electrons to NMR-active nuclei. Despite its success in elucidating important structural information on biological and inorganic materials, the detailed polarization-transfer pathway from the electrons to the nearby and then the bulk solvent nuclei, and finally to the molecules of interest-remains unclear. In particular, the nuclei in the paramagnetic polarizing agent play significant roles in relaying the enhanced NMR polarizations to more remote nuclei. Despite their importance, the direct NMR observation of these nuclei is challenging because of poor sensitivity. Here, we show that a combined DNP and electron decoupling approach can facilitate direct NMR detection of these nuclei. We achieved an ∼80 % improvement in NMR intensity via electron decoupling at 0.35 T and 80 K on trityl radicals. Moreover, we recorded a DNP enhancement factor of ϵ ${\varepsilon{} }$ ∼90 and ∼11 % higher NMR intensity using electron decoupling on paramagnetic metal-organic framework, magnesium hexaoxytriphenylene (MgHOTP MOF).
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Affiliation(s)
- Kong Ooi Tan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 (USA),Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA-02139 (USA),Laboratoire des Biomolécules, LBM, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris (France)
| | - Luming Yang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 (USA),Research Group EPR Spectroscopy, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077 (Germany)
| | - Michael Mardini
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 (USA),Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA-02139 (USA)
| | - Choon Boon Cheong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 (USA),Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA-02139 (USA),Institute of Sustainability for ChemicalsEnergy and Environment, 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore)
| | - Benoit Driesschaert
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV-2650 (USA)
| | - Mircea Dincă
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA-02139 (USA)
| | - Robert G. 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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13
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Chow WY, De Paëpe G, Hediger S. Biomolecular and Biological Applications of Solid-State NMR with Dynamic Nuclear Polarization Enhancement. Chem Rev 2022; 122:9795-9847. [PMID: 35446555 DOI: 10.1021/acs.chemrev.1c01043] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Solid-state NMR spectroscopy (ssNMR) with magic-angle spinning (MAS) enables the investigation of biological systems within their native context, such as lipid membranes, viral capsid assemblies, and cells. However, such ambitious investigations often suffer from low sensitivity due to the presence of significant amounts of other molecular species, which reduces the effective concentration of the biomolecule or interaction of interest. Certain investigations requiring the detection of very low concentration species remain unfeasible even with increasing experimental time for signal averaging. By applying dynamic nuclear polarization (DNP) to overcome the sensitivity challenge, the experimental time required can be reduced by orders of magnitude, broadening the feasible scope of applications for biological solid-state NMR. In this review, we outline strategies commonly adopted for biological applications of DNP, indicate ongoing challenges, and present a comprehensive overview of biological investigations where MAS-DNP has led to unique insights.
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Affiliation(s)
- Wing Ying Chow
- Univ. Grenoble Alpes, CEA, CNRS, Interdisciplinary Research Institute of Grenoble (IRIG), Modeling and Exploration of Materials Laboratory (MEM), 38054 Grenoble, France.,Univ. Grenoble Alpes, CEA, CNRS, Inst. Biol. Struct. IBS, 38044 Grenoble, France
| | - Gaël De Paëpe
- Univ. Grenoble Alpes, CEA, CNRS, Interdisciplinary Research Institute of Grenoble (IRIG), Modeling and Exploration of Materials Laboratory (MEM), 38054 Grenoble, France
| | - Sabine Hediger
- Univ. Grenoble Alpes, CEA, CNRS, Interdisciplinary Research Institute of Grenoble (IRIG), Modeling and Exploration of Materials Laboratory (MEM), 38054 Grenoble, France
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14
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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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15
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Biedenbänder T, Aladin V, Saeidpour S, Corzilius B. Dynamic Nuclear Polarization for Sensitivity Enhancement in Biomolecular Solid-State NMR. Chem Rev 2022; 122:9738-9794. [PMID: 35099939 DOI: 10.1021/acs.chemrev.1c00776] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Solid-state NMR with magic-angle spinning (MAS) is an important method in structural biology. While NMR can provide invaluable information about local geometry on an atomic scale even for large biomolecular assemblies lacking long-range order, it is often limited by low sensitivity due to small nuclear spin polarization in thermal equilibrium. Dynamic nuclear polarization (DNP) has evolved during the last decades to become a powerful method capable of increasing this sensitivity by two to three orders of magnitude, thereby reducing the valuable experimental time from weeks or months to just hours or days; in many cases, this allows experiments that would be otherwise completely unfeasible. In this review, we give an overview of the developments that have opened the field for DNP-enhanced biomolecular solid-state NMR including state-of-the-art applications at fast MAS and high magnetic field. We present DNP mechanisms, polarizing agents, and sample constitution methods suitable for biomolecules. A wide field of biomolecular NMR applications is covered including membrane proteins, amyloid fibrils, large biomolecular assemblies, and biomaterials. Finally, we present perspectives and recent developments that may shape the field of biomolecular DNP in the future.
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Affiliation(s)
- Thomas Biedenbänder
- Institute of Chemistry, University of Rostock, Albert-Einstein-Straße 3a, 18059 Rostock, Germany.,Department Life, Light & Matter, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany
| | - Victoria Aladin
- Institute of Chemistry, University of Rostock, Albert-Einstein-Straße 3a, 18059 Rostock, Germany.,Department Life, Light & Matter, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany
| | - Siavash Saeidpour
- Institute of Chemistry, University of Rostock, Albert-Einstein-Straße 3a, 18059 Rostock, Germany.,Department Life, Light & Matter, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany
| | - Björn Corzilius
- Institute of Chemistry, University of Rostock, Albert-Einstein-Straße 3a, 18059 Rostock, Germany.,Department Life, Light & Matter, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany
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16
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Delage-Laurin L, Palani RS, Golota N, Mardini M, Ouyang Y, Tan KO, Swager TM, Griffin RG. Overhauser Dynamic Nuclear Polarization with Selectively Deuterated BDPA Radicals. J Am Chem Soc 2021; 143:20281-20290. [PMID: 34813311 DOI: 10.1021/jacs.1c09406] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The Overhauser effect (OE), commonly observed in NMR spectra of liquids and conducting solids, was recently discovered in insulating solids doped with the radical 1,3-bisdiphenylene-2-phenylallyl (BDPA). However, the mechanism of polarization transfer in OE-DNP in insulators is yet to be established, but hyperfine coupling of the radical to protons in BDPA has been proposed. In this paper we present a study that addresses the role of hyperfine couplings via the EPR and DNP measurements on some selectively deuterated BDPA radicals synthesized for this purpose. Newly developed synthetic routes enable selective deuteration at orthogonal positions or perdeuteration of the fluorene moieties with 2H incorporation of >93%. The fluorene moieties were subsequently used to synthesize two octadeuterated BDPA radicals, 1,3-[α,γ-d8]-BDPA and 1,3-[β,δ-d8]-BDPA, and a BDPA radical with perdeuterated fluorene moieties, 1,3-[α,β,γ,δ-d16]-BDPA. In contrast to the strong positive OE enhancement observed in degassed samples of fully protonated h21-BDPA (ε ∼ +70), perdeuteration of the fluorenes results in a negative enhancement (ε ∼ -13), while selective deuteration of α- and γ-positions (aiso ∼ 5.4 MHz) in BDPA results in a weak negative OE enhancement (ε ∼ -1). Furthermore, deuteration of β- and δ-positions (aiso ∼ 1.2 MHz) results in a positive OE enhancement (ε ∼ +36), albeit with a reduced magnitude relative to that observed in fully protonated BDPA. Our results clearly show the role of the hyperfine coupled α and γ 1H spins in the BDPA radical in determining the dominance of the zero and double-quantum cross-relaxation pathways and the polarization-transfer mechanism to the bulk matrix.
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Affiliation(s)
- Léo Delage-Laurin
- Institute for Soldier Nanotechnologies, Cambridge, Massachusetts 02139, United States
| | | | | | | | | | | | - Timothy M Swager
- Institute for Soldier Nanotechnologies, Cambridge, Massachusetts 02139, United States
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17
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Equbal A, Jain SK, Li Y, Tagami K, Wang X, Han S. Role of electron spin dynamics and coupling network in designing dynamic nuclear polarization. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2021; 126-127:1-16. [PMID: 34852921 DOI: 10.1016/j.pnmrs.2021.05.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Accepted: 05/22/2021] [Indexed: 06/13/2023]
Abstract
Dynamic nuclear polarization (DNP) has emerged as a powerful sensitivity booster of nuclear magnetic resonance (NMR) spectroscopy for the characterization of biological solids, catalysts and other functional materials, but is yet to reach its full potential. DNP transfers the high polarization of electron spins to nuclear spins using microwave irradiation as a perturbation. A major focus in DNP research is to improve its efficiency at conditions germane to solid-state NMR, at high magnetic fields and fast magic-angle spinning. In this review, we highlight three key strategies towards designing DNP experiments: time-domain "smart" microwave manipulation to optimize and/or modulate electron spin polarization, EPR detection under operational DNP conditions to decipher the underlying electron spin dynamics, and quantum mechanical simulations of coupled electron spins to gain microscopic insights into the DNP mechanism. These strategies are aimed at understanding and modeling the properties of the electron spin dynamics and coupling network. The outcome of these strategies is expected to be key to developing next-generation polarizing agents and DNP methods.
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Affiliation(s)
- Asif Equbal
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Sheetal Kumar Jain
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Yuanxin Li
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Kan Tagami
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Xiaoling Wang
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States; Department of Physics, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Songi Han
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, CA 93106, United States; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, United States.
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18
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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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19
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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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20
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Park H, Uluca-Yazgi B, Heumann S, Schlögl R, Granwehr J, Heise H, Schleker PPM. Heteronuclear cross-relaxation effect modulated by the dynamics of N-functional groups in the solid state under 15N DP-MAS DNP. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 312:106688. [PMID: 32004819 DOI: 10.1016/j.jmr.2020.106688] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 01/12/2020] [Accepted: 01/14/2020] [Indexed: 06/10/2023]
Abstract
In a typical magic-angle spinning (MAS) dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) experiment, several mechanisms are simultaneously involved when transferring much larger polarization of electron spins to NMR active nuclei of interest. Recently, specific cross-relaxation enhancement by active motions under DNP (SCREAM-DNP) [Daube et al. JACS 2016] has been reported as one of these mechanisms. Thereby 13C enhancement with inverted sign was observed in a direct polarization (DP) MAS DNP experiment, caused by reorientation dynamics of methyl that was not frozen out at 100 K. Here, we report on the spontaneous polarization transfer from hyperpolarized 1H to both primary amine and ammonium nitrogens, resulting in an additional positive signal enhancement in the 15N NMR spectra during 15N DP-MAS DNP. The cross-relaxation induced signal enhancement (CRE) for 15N is of opposite sign compared to that observed for 13C due to the negative sign of the gyromagnetic ratio of 15N. The influence on CRE efficiency caused by variation of the radical solution composition and by temperature was also investigated.
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Affiliation(s)
- Heeyong Park
- Max Planck Institute for Chemical Energy Conversion, Department of Heterogeneous Reactions, 45470 Mülheim an der Ruhr, Germany; Forschungszentrum Jülich, IEK-9, 52425 Jülich, Germany; RWTH Aachen University, Institute of Technical and Macromolecular Chemistry, 52074 Aachen, Germany
| | - Boran Uluca-Yazgi
- Forschungszentrum Jülich, IBI-7 and JuStruct, 52425 Jülich, Germany; Heinrich Heine Universität Düsseldorf, Institute of Physical Biology, 40225 Düsseldorf, Germany
| | - Saskia Heumann
- Max Planck Institute for Chemical Energy Conversion, Department of Heterogeneous Reactions, 45470 Mülheim an der Ruhr, Germany
| | - Robert Schlögl
- Max Planck Institute for Chemical Energy Conversion, Department of Heterogeneous Reactions, 45470 Mülheim an der Ruhr, Germany; Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany
| | - Josef Granwehr
- Forschungszentrum Jülich, IEK-9, 52425 Jülich, Germany; RWTH Aachen University, Institute of Technical and Macromolecular Chemistry, 52074 Aachen, Germany
| | - Henrike Heise
- Forschungszentrum Jülich, IBI-7 and JuStruct, 52425 Jülich, Germany; Heinrich Heine Universität Düsseldorf, Institute of Physical Biology, 40225 Düsseldorf, Germany
| | - P Philipp M Schleker
- Max Planck Institute for Chemical Energy Conversion, Department of Heterogeneous Reactions, 45470 Mülheim an der Ruhr, Germany; Forschungszentrum Jülich, IEK-9, 52425 Jülich, Germany.
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21
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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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22
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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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23
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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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24
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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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25
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Gao C, Alaniva N, Saliba EP, Sesti EL, Judge PT, Scott FJ, Halbritter T, Sigurdsson ST, Barnes AB. Frequency-chirped dynamic nuclear polarization with magic angle spinning using a frequency-agile gyrotron. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 308:106586. [PMID: 31525550 DOI: 10.1016/j.jmr.2019.106586] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 08/15/2019] [Accepted: 08/28/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate that frequency-chirped dynamic nuclear polarization (DNP) with magic angle spinning (MAS) improves the enhancement of nuclear magnetic resonance (NMR) signal beyond that of continuous-wave (CW) DNP. Using a custom, frequency-agile gyrotron we implemented frequency-chirped DNP using the TEMTriPol-1 biradical, with MAS NMR at 7 T. Frequency-chirped microwaves yielded a DNP enhancement of 137, an increase of 19% compared to 115 recorded with CW. The chirps were 120 MHz-wide and centered over the trityl resonance, with 7 W microwave power incident on the sample (estimated 0.4 MHz electron spin Rabi frequency). We describe in detail the design and fabrication of the frequency-agile gyrotron used for frequency-chirped MAS DNP. Improvements to the interaction cavity and internal mode converter yielded efficient microwave generation and mode conversion, achieving >10 W output power over a 335 MHz bandwidth with >110 W peak power. Frequency-chirped DNP with MAS is expected to have a significant impact on the future of magnetic resonance.
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Affiliation(s)
- Chukun Gao
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA; Physical Chemistry, ETH-Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Nicholas Alaniva
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA; Physical Chemistry, ETH-Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Edward P Saliba
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA; Physical Chemistry, ETH-Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Erika L Sesti
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Patrick T Judge
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA; Department of Biochemistry, Biophysics & Structural Biology, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Faith J Scott
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Thomas Halbritter
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
| | - Snorri Th Sigurdsson
- University of Iceland, Department of Chemistry, Science Institute, Dunhaga 3, 107 Reykjavik, Iceland
| | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA; Physical Chemistry, ETH-Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland.
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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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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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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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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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30
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Aladin V, Corzilius B. Methyl dynamics in amino acids modulate heteronuclear cross relaxation in the solid state under MAS DNP. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 99:27-35. [PMID: 30865870 DOI: 10.1016/j.ssnmr.2019.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 02/20/2019] [Accepted: 02/20/2019] [Indexed: 05/09/2023]
Abstract
Dynamic Nuclear Polarization (DNP) is a wide-spread technique for sensitivity enhancement of MAS NMR. During a typical MAS DNP experiment, several mechanisms resulting in polarization transfer may be active at the same time. One such mechanism which is most commonly active but up to now mostly disregarded is SCREAM-DNP (Specific Cross Relaxation Enhancement by Active Motions under DNP). This effect is generally observed in direct DNP experiments if molecular dynamics are supporting heteronuclear cross relaxation similar to the nuclear Overhauser effect. We investigate this effect for the CH3 groups of all methyl-bearing amino acids (i.e., alanine, valine, leucine, isoleucine, threonine, and methionine). At the typical DNP temperature of ∼110 K the three-fold reorientation dynamics are still active, and efficient SCREAM-DNP is observed. We discuss variations in enhancement factors obtained by this effect in context of sample temperature and sterical hindrance of the methyl group. Next to the direct transfer to the methyl carbon, we also find evidence for much weaker transfer from the methyl protons directly to other carbons in the amino acid molecule and succeed to correlate build-up dynamics with the CH dipole coupling which is modulated by the CH3 orientation. Besides methyl dynamics we also identify ring dynamics within proline as a source of SCREAM-DNP. Our results are the first step towards utilization of this effect as a specific probing techniqueusing methyl groups in protein systems.
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Affiliation(s)
- Victoria Aladin
- Institute of Physical Chemistry, Institute of Biophysical Chemistry, Biomolecular Magnetic Resonance Center (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438, Frankfurt, Germany
| | - Björn Corzilius
- Institute of Physical Chemistry, Institute of Biophysical Chemistry, Biomolecular Magnetic Resonance Center (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438, Frankfurt, Germany.
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31
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Gao C, Judge PT, Sesti EL, Price LE, Alaniva N, Saliba EP, Albert BJ, Soper NJ, Chen PH, Barnes AB. Four millimeter spherical rotors spinning at 28 kHz with double-saddle coils for cross polarization NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 303:1-6. [PMID: 30978570 DOI: 10.1016/j.jmr.2019.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/07/2019] [Accepted: 03/20/2019] [Indexed: 06/09/2023]
Abstract
Spherical rotors in magic angle spinning (MAS) experiments have significant advantages over traditional cylindrical rotors including simplified spinning implementation, easy sample exchange, more efficient microwave coupling for dynamic nuclear polarization (DNP), and feasibility of downscaling to access higher spinning frequencies. Here, we implement spherical rotors with 4 mm outside diameter (o.d.) and demonstrate spinning >28 kHz using a single aperture for spinning gas. We show a modified stator geometry to improve fiber optic detection, increase NMR filling factor, and improve alignment for sample exchange and microwave irradiation. Higher NMR Rabi frequencies were obtained using smaller radiofrequency (RF) coils on small-diameter spherical rotors, compared to our previous implementation of MAS spheres with an o.d. of 9.5 mm. We report nutation fields of 110 kHz on 13C with 820 W of input power and 100 kHz on 1H with 800 W of input power. Proton decoupling fields of 78 kHz were applied over 20 ms of signal acquisition without any sign of arcing. Compared to our initial demonstration of a split coil for 9.5 mm spheres, this current implementation of a double-saddle coil inductor for 4 mm spheres not only intensifies the RF fields, but also improves RF homogeneity. We achieve an 810°/90° nutation intensity ratio of 0.84 at 300.197 MHz (1H). We also show electromagnetic simulations predicting a nearly 3-fold improvement in electron Rabi frequency of 0.99 MHz (with 4 mm spheres) compared to 0.38 MHz (with 3.2 mm cylinders), with 5 W of incident microwave power. Further improvements in magnetic resonance spin control are expected as RF inductors and microwave coupling are optimized for spherical rotors and scaled down to the micron scale.
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Affiliation(s)
- Chukun Gao
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Patrick T Judge
- Department of Chemistry, Washington University in St. Louis, 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, St. Louis, MO 63130, USA
| | - Lauren E Price
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Nicholas Alaniva
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Edward P Saliba
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Brice J Albert
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Nathan J Soper
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - 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
| | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
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32
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Scott FJ, Alaniva N, Golota NC, Sesti EL, Saliba EP, Price LE, Albert BJ, Chen P, O'Connor RD, Barnes AB. A versatile custom cryostat for dynamic nuclear polarization supports multiple cryogenic magic angle spinning transmission line probes. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 297:23-32. [PMID: 30342370 DOI: 10.1016/j.jmr.2018.10.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/29/2018] [Accepted: 10/02/2018] [Indexed: 06/08/2023]
Abstract
Dynamic nuclear polarization (DNP) with cryogenic magic angle spinning (MAS) provides significant improvements in NMR sensitivity, yet presents unique technical challenges. Here we describe a custom cryostat and suite of NMR probes capable of manipulating nuclear spins with multi-resonant radiofrequency circuits, cryogenic spinning below 6 K, sample exchange, and microwave coupling for DNP. The corrugated waveguide and six transfer lines needed for DNP and cryogenic spinning functionality are coupled to the probe from the top of the magnet. Transfer lines are vacuum-jacketed and provide bearing and drive gas, variable temperature fluid, two exhaust pathways, and a sample ejection port. The cryostat thermally isolates the magnet bore, thereby protecting the magnet and increasing cryogen efficiency. This novel design supports cryogenic MAS-DNP performance over an array of probes without altering DNP functionality. We present three MAS probes (two supporting 3.2 mm rotors and one supporting 9.5 mm rotors) interfacing with the single cryostat. Mechanical details, transmission line radio frequency design, and performance of the cryostat and three probes are described.
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Affiliation(s)
- Faith J Scott
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Nicholas Alaniva
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Natalie C Golota
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Erika L Sesti
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Edward P Saliba
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Lauren E Price
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Brice J Albert
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Pinhui 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
| | - Robert D O'Connor
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
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Sesti EL, Saliba EP, Alaniva N, Barnes AB. Electron decoupling with cross polarization and dynamic nuclear polarization below 6 K. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 295:1-5. [PMID: 30077145 PMCID: PMC7015119 DOI: 10.1016/j.jmr.2018.07.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 07/17/2018] [Accepted: 07/21/2018] [Indexed: 05/05/2023]
Abstract
Dynamic nuclear polarization (DNP) can improve nuclear magnetic resonance (NMR) sensitivity by orders of magnitude. Polarizing agents containing unpaired electrons required for DNP can broaden nuclear resonances in the presence of appreciable hyperfine couplings. Here we present the first cross polarization experiments implemented with electron decoupling, which attenuates detrimental hyperfine couplings. We also demonstrate magic angle spinning (MAS) DNP experiments below 6 K, producing unprecedented nuclear spin polarization in rotating solids. 13C correlation spectra were collected with MAS DNP below 6 K for the first time. Polarization build-up times with MAS DNP (T1DNP, 1H) of urea in a frozen glassy matrix below 6 K were measured for both the solid effect and the cross effect. Trityl radicals exhibit a T1DNP (1H) of 18.7 s and the T1DNP (1H) of samples doped with 20 mM AMUPol is only 1.3 s. MAS below 6 K with DNP and electron decoupling is an effective strategy to increase NMR signal-to-noise ratios per transient while retaining short polarization periods.
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Affiliation(s)
- 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
| | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA.
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Saliba E, Sesti EL, Alaniva N, Barnes AB. Pulsed Electron Decoupling and Strategies for Time Domain Dynamic Nuclear Polarization with Magic Angle Spinning. J Phys Chem Lett 2018; 9:5539-5547. [PMID: 30180584 PMCID: PMC6151657 DOI: 10.1021/acs.jpclett.8b01695] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 09/04/2018] [Indexed: 05/05/2023]
Abstract
Magic angle spinning (MAS) dynamic nuclear polarization (DNP) is widely used to increase nuclear magnetic resonance (NMR) signal intensity. Frequency-chirped microwaves yield superior control of electron spins and are expected to play a central role in the development of DNP MAS experiments. Time domain electron control with MAS has considerable promise to improve DNP performance at higher fields and temperatures. We have recently demonstrated that pulsed electron decoupling using frequency-chirped microwaves improves MAS DNP experiments by partially attenuating detrimental hyperfine interactions. The continued development of pulsed electron decoupling will enable a new suite of MAS DNP experiments that transfer polarization directly to observed spins. Time domain DNP transfers to nuclear spins in conjunction with pulsed electron decoupling is described as a viable avenue toward DNP-enhanced, high-resolution NMR spectroscopy over a range of temperatures from <6 to 320 K.
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Affiliation(s)
- Edward
P. Saliba
- Department of Chemistry, Washington
University in St. Louis, St. Louis, Missouri 63130, United States
| | - Erika L. Sesti
- 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
| | - Alexander B. Barnes
- Department of Chemistry, Washington
University in St. Louis, St. Louis, Missouri 63130, United States
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35
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Albert BJ, Gao C, Sesti EL, Saliba EP, Alaniva N, Scott FJ, Sigurdsson ST, Barnes AB. Dynamic Nuclear Polarization Nuclear Magnetic Resonance in Human Cells Using Fluorescent Polarizing Agents. Biochemistry 2018; 57:4741-4746. [PMID: 29924582 DOI: 10.1021/acs.biochem.8b00257] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Solid state nuclear magnetic resonance (NMR) enables atomic-resolution characterization of the molecular structure and dynamics within complex heterogeneous samples, but it is typically insensitive. Dynamic nuclear polarization (DNP) increases the NMR signal intensity by orders of magnitude and can be performed in combination with magic angle spinning (MAS) for sensitive, high-resolution spectroscopy. Here we report MAS DNP experiments, for the first time, within intact human cells with >40-fold DNP enhancement and a sample temperature of <6 K. In addition to cryogenic MAS results at <6 K, we also show in-cell DNP enhancements of 57-fold at 90 K. In-cell DNP is demonstrated using biradicals and sterically shielded monoradicals as polarizing agents. A novel trimodal polarizing agent is introduced for DNP, which contains a nitroxide biradical, a targeting peptide for cell penetration, and a fluorophore for subcellular localization with confocal microscopy. The fluorescent polarizing agent provides in-cell DNP enhancements of 63-fold at a concentration of 2.7 mM. These experiments pave the way for structural characterization of biomolecules in an endogenous cellular context.
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Affiliation(s)
- Brice J Albert
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Chukun Gao
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Erika L Sesti
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Edward P Saliba
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Nicholas Alaniva
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Faith J Scott
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Snorri Th Sigurdsson
- University of Iceland , Department of Chemistry, Science Institute , Dunhaga 3 , 107 Reykjavik , Iceland
| | - Alexander B Barnes
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
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Wittmann JJ, Eckardt M, Harneit W, Corzilius B. Electron-driven spin diffusion supports crossing the diffusion barrier in MAS DNP. Phys Chem Chem Phys 2018; 20:11418-11429. [PMID: 29645035 DOI: 10.1039/c8cp00265g] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Dynamic nuclear polarization (DNP) can be applied to enhance the sensitivity of solid-state NMR experiments by several orders of magnitude due to microwave-driven transfer of spin polarization from unpaired electrons to nuclei. While the underlying quantum mechanical aspects are sufficiently well understood on a microscopic level, the exact description of the large-scale spin dynamics, usually involving hundreds to thousands of nuclear spins per electron, is still lacking consensus. Generally, it is assumed that nuclear hyperpolarization can only be observed on nuclei which do not experience strong influence of the unpaired electrons and thus being significantly removed from the paramagnetic polarizing agents. At the same time, sufficiently strong hyperfine interaction is required for DNP transfer. Therefore, efficient nuclear spin diffusion from the strongly-interacting nuclei to the NMR-observable bulk is considered to be essential for efficient nuclear hyperpolarization. Based on experimental results obtained on the endohedral fullerene N@C60 as a polarizing agent sparsely diluted in C60, we discuss the effect of the spin-diffusion barrier. We introduce electron-driven spin diffusion (EDSD) as a novel mechanism for nuclear polarization transfer in the proximity of an electron spin which is particularly relevant under magic-angle spinning (MAS) DNP conditions.
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Affiliation(s)
- Johannes J Wittmann
- Institute of Physical and Theoretical Chemistry, Institute of Biophysical Chemistry, and Biomolecular Magnetic Resonance Center (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany.
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