1
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Beriashvili D, Yao R, D'Amico F, Krafčíková M, Gurinov A, Safeer A, Cai X, Mulder MPC, Liu Y, Folkers GE, Baldus M. A high-field cellular DNP-supported solid-state NMR approach to study proteins with sub-cellular specificity. Chem Sci 2023; 14:9892-9899. [PMID: 37736634 PMCID: PMC10510770 DOI: 10.1039/d3sc02117c] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 08/24/2023] [Indexed: 09/23/2023] Open
Abstract
Studying the structural aspects of proteins within sub-cellular compartments is of growing interest. Dynamic nuclear polarization supported solid-state NMR (DNP-ssNMR) is uniquely suited to provide such information, but critically lacks the desired sensitivity and resolution. Here we utilize SNAPol-1, a novel biradical, to conduct DNP-ssNMR at high-magnetic fields (800 MHz/527 GHz) inside HeLa cells and isolated cell nuclei electroporated with [13C,15N] labeled ubiquitin. We report that SNAPol-1 passively diffuses and homogenously distributes within whole cells and cell nuclei providing ubiquitin spectra of high sensitivity and remarkably improved spectral resolution. For cell nuclei, physical enrichment facilitates a further 4-fold decrease in measurement time and provides an exclusive structural view of the nuclear ubiquitin pool. Taken together, these advancements enable atomic interrogation of protein conformational plasticity at atomic resolution and with sub-cellular specificity.
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Affiliation(s)
- David Beriashvili
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University Padualaan 8 3584 CH Utrecht The Netherlands
| | - Ru Yao
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University Tianjin 300070 P. R. China
| | - Francesca D'Amico
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC) Einthovenweg 20 2333 ZC Leiden The Netherlands
| | - Michaela Krafčíková
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University Padualaan 8 3584 CH Utrecht The Netherlands
| | - Andrei Gurinov
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University Padualaan 8 3584 CH Utrecht The Netherlands
| | - Adil Safeer
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University Padualaan 8 3584 CH Utrecht The Netherlands
| | - Xinyi Cai
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University Tianjin 300070 P. R. China
| | - Monique P C Mulder
- Department of Cell and Chemical Biology, Leiden University Medical Center (LUMC) Einthovenweg 20 2333 ZC Leiden The Netherlands
| | - Yangping Liu
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University Tianjin 300070 P. R. China
| | - Gert E Folkers
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University Padualaan 8 3584 CH Utrecht The Netherlands
| | - Marc Baldus
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University Padualaan 8 3584 CH Utrecht The Netherlands
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2
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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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3
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Lends A, Birlirakis N, Cai X, Daskalov A, Shenoy J, Abdul-Shukkoor MB, Berbon M, Ferrage F, Liu Y, Loquet A, Tan KO. Efficient 18.8 T MAS-DNP NMR reveals hidden side chains in amyloid fibrils. JOURNAL OF BIOMOLECULAR NMR 2023:10.1007/s10858-023-00416-5. [PMID: 37289306 DOI: 10.1007/s10858-023-00416-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 05/02/2023] [Indexed: 06/09/2023]
Abstract
Amyloid fibrils are large and insoluble protein assemblies composed of a rigid core associated with a cross-β arrangement rich in β-sheet structural elements. It has been widely observed in solid-state NMR experiments that semi-rigid protein segments or side chains do not yield easily observable NMR signals at room temperature. The reasons for the missing peaks may be due to the presence of unfavorable dynamics that interfere with NMR experiments, which result in very weak or unobservable NMR signals. Therefore, for amyloid fibrils, semi-rigid and dynamically disordered segments flanking the amyloid core are very challenging to study. Here, we show that high-field dynamic nuclear polarization (DNP), an NMR hyperpolarization technique typically performed at low temperatures, can circumvent this issue because (i) the low-temperature environment (~ 100 K) slows down the protein dynamics to escape unfavorable detection regime, (ii) DNP improves the overall NMR sensitivity including those of flexible side chains, and (iii) efficient cross-effect DNP biradicals (SNAPol-1) optimized for high-field DNP (≥ 18.8 T) are employed to offer high sensitivity and resolution suitable for biomolecular NMR applications. By combining these factors, we have successfully established an impressive enhancement factor of ε ~ 50 on amyloid fibrils using an 18.8 T/ 800 MHz magnet. We have compared the DNP efficiencies of M-TinyPol, NATriPol-3, and SNAPol-1 biradicals on amyloid fibrils. We found that SNAPol-1 (with ε ~ 50) outperformed the other two radicals. The MAS DNP experiments revealed signals of flexible side chains previously inaccessible at conventional room-temperature experiments. These results demonstrate the potential of MAS-DNP NMR as a valuable tool for structural investigations of amyloid fibrils, particularly for side chains and dynamically disordered segments otherwise hidden at room temperature.
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Affiliation(s)
- Alons Lends
- CNRS, Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR 5348, Institut Europeen de Chimie et Biologie (IECB), University of Bordeaux, 33600, Pessac, France
| | - Nicolas Birlirakis
- Laboratoire des Biomolécules, LBM, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - Xinyi Cai
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, China
| | - Asen Daskalov
- CNRS, Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR 5348, Institut Europeen de Chimie et Biologie (IECB), University of Bordeaux, 33600, Pessac, France
| | - Jayakrishna Shenoy
- CNRS, Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR 5348, Institut Europeen de Chimie et Biologie (IECB), University of Bordeaux, 33600, Pessac, France
| | - Muhammed Bilal Abdul-Shukkoor
- CNRS, Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR 5348, Institut Europeen de Chimie et Biologie (IECB), University of Bordeaux, 33600, Pessac, France
| | - Mélanie Berbon
- CNRS, Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR 5348, Institut Europeen de Chimie et Biologie (IECB), University of Bordeaux, 33600, Pessac, France
| | - Fabien Ferrage
- Laboratoire des Biomolécules, LBM, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - Yangping Liu
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, China
| | - Antoine Loquet
- CNRS, Chemistry and Biology of Membranes and Nanoobjects (CBMN), UMR 5348, Institut Europeen de Chimie et Biologie (IECB), University of Bordeaux, 33600, Pessac, France.
| | - Kong Ooi Tan
- Laboratoire des Biomolécules, LBM, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France.
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4
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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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5
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Chandler B, Todd L, Smith SO. Magic angle spinning NMR of G protein-coupled receptors. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2022; 128:25-43. [PMID: 35282868 PMCID: PMC10718405 DOI: 10.1016/j.pnmrs.2021.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/26/2021] [Accepted: 10/27/2021] [Indexed: 06/14/2023]
Abstract
G protein-coupled receptors (GPCRs) have a simple seven transmembrane helix architecture which has evolved to recognize a diverse number of chemical signals. The more than 800 GPCRs encoded in the human genome function as receptors for vision, smell and taste, and mediate key physiological processes. Consequently, these receptors are a major target for pharmaceuticals. Protein crystallography and electron cryo-microscopy have provided high resolution structures of many GPCRs in both active and inactive conformations. However, these structures have not sparked a surge in rational drug design, in part because GPCRs are inherently dynamic and the structural changes induced by ligand or drug binding to stabilize inactive or active conformations are often subtle rearrangements in packing or hydrogen-bonding interactions. NMR spectroscopy provides a sensitive probe of local structure and dynamics at specific sites within these receptors as well as global changes in receptor structure and dynamics. These methods can also capture intermediate states and conformations with low populations that provide insights into the activation pathways. We review the use of solid-state magic angle spinning NMR to address the structure and activation mechanisms of GPCRs. The focus is on the large and diverse class A family of receptors. We highlight three specific class A GPCRs in order to illustrate how solid-state, as well as solution-state, NMR spectroscopy can answer questions in the field involving how different GPCR classes and subfamilies are activated by their associated ligands, and how small molecule drugs can modulate GPCR activation.
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Affiliation(s)
- Bianca Chandler
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, United States.
| | - Lauren Todd
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, United States.
| | - Steven O Smith
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, United States.
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6
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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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7
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Can TV, Tan KO, Yang C, Weber RT, Griffin RG. Time domain DNP at 1.2 T. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 329:107012. [PMID: 34186299 PMCID: PMC9148420 DOI: 10.1016/j.jmr.2021.107012] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/26/2021] [Accepted: 05/27/2021] [Indexed: 05/28/2023]
Abstract
We present the results of an experimental pulsed DNP study at 1.2 T (33.5 GHz/51 MHz electron and 1H Larmor frequencies, respectively). The results include a comparison of constant-amplitude NOVEL (CA-NOVEL), ramped-amplitude NOVEL (RA-NOVEL) and the frequency-swept integrated solid effect (FS-ISE) experiments all of which were performed at the NOVEL matching condition, ω1S=ω0I, where ω1S is the electron Rabi frequency andω0I the proton Larmor frequency. To the best of our knowledge, this is the first pulsed DNP study carried out at field higher than X-band (0.35 T) using the NOVEL condition. A combination of high microwave power (∼150 W) and a microwave cavity with a high Q (∼500) allowed us to satisfy the NOVEL matching condition. We also observed stretched solid effect (S2E) contributions in the Zeeman field profiles when chirped pulses are applied. Furthermore, the high quality factor of the cavity limits the concentration of the radical to ∼5 mM and generates a hysteresis in the FS-ISE experiments. Nevertheless, we observe very high DNP enhancements that are comparable to the results at X-band. These promising outcomes suggest the importance of further studies at even higher fields that delineate the instrumentation and methods required for time domain DNP.
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Affiliation(s)
- T V Can
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - K O Tan
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - C Yang
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - R T Weber
- Bruker BioSpin Corporation, Billerica, MA 01821, United States
| | - R G Griffin
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
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8
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Hughes A, Liu M, Paul S, Cooper AI, Blanc F. Dynamics in Flexible Pillar[ n]arenes Probed by Solid-State NMR. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:13370-13381. [PMID: 34239656 PMCID: PMC8237263 DOI: 10.1021/acs.jpcc.1c02046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 05/07/2021] [Indexed: 06/13/2023]
Abstract
Pillar[n]arenes are supramolecular assemblies that can perform a range of technologically important molecular separations which are enabled by their molecular flexibility. Here, we probe dynamical behavior by performing a range of variable-temperature solid-state NMR experiments on microcrystalline perethylated pillar[n]arene (n = 5, 6) and the corresponding three pillar[6]arene xylene adducts in the 100-350 K range. This was achieved either by measuring site-selective motional averaged 13C 1H heteronuclear dipolar couplings and subsequently accessing order parameters or by determining 1H and 13C spin-lattice relaxation times and extracting correlation times based on dipolar and/or chemical shift anisotropy relaxation mechanisms. We demonstrate fast motional regimes at room temperature and highlight a significant difference in dynamics between the core of the pillar[n]arenes, the protruding flexible ethoxy groups, and the adsorbed xylene guest. Additionally, unexpected and sizable 13C 1H heteronuclear dipolar couplings for a quaternary carbon were observed for p-xylene adsorbed in pillar[6]arene only, indicating a strong host-guest interaction and establishing the p-xylene location inside the host, confirming structural refinements.
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Affiliation(s)
- Ashlea
R. Hughes
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United
Kingdom
| | - Ming Liu
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United
Kingdom
- Materials
Innovation Factory, University of Liverpool, 51 Oxford Street, Liverpool, L7 3NY, United Kingdom
| | - Subhradip Paul
- Nottingham
DNP MAS NMR Facility, Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - Andrew I. Cooper
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United
Kingdom
- Materials
Innovation Factory, University of Liverpool, 51 Oxford Street, Liverpool, L7 3NY, United Kingdom
| | - Frédéric Blanc
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United
Kingdom
- Stephenson
Institute for Renewable Energy, University
of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom
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9
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Akbey Ü. Dynamics of uniformly labelled solid proteins between 100 and 300 K: A 2D 2H- 13C MAS NMR approach. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 327:106974. [PMID: 33823335 DOI: 10.1016/j.jmr.2021.106974] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 03/20/2021] [Accepted: 03/20/2021] [Indexed: 06/12/2023]
Abstract
We describe a 2H based MAS nuclear magnetic resonance (NMR) method to obtain site-specific molecular dynamics of biomolecules. The method utilizes the use of deuterium nucleus as a spin label that is proven to be very useful in dynamics studies of solid biological and functional materials. The aim is to understand overall characteristics of protein backbone and side-chain motions for CD3, CD2 and CD groups, in terms of timescale, type and activation energy of the underlying processes. Variable temperature two-dimensional (2D) 2H-13C correlation MAS NMR spectra were recorded for the uniformly 2H,13C,15N labelled Alanine and microcrystalline SH3 at a broad temperature range, from 320 K down to 100 K. First, the deuterium quadrupolar-coupling constant from specific D-C sites is obtained with the 2D experiment by utilizing carbon chemical shifts. Second, the static quadrupolar patterns are obtained at 100 K. Third, variable temperature approach enabled the observation of quadrupolar pattern over different motional regimes; slow, intermediate and fast. And finally, the apparent activation energies for C-D sites are determined and compared, by evaluating the temperature induced signal intensities. This information led to the determination of the dynamic processes for different D-C sites at a broad range of temperature and motional timescales. This is a first representation of 2D 2H-13C MAS NMR approach applied to fully isotope labelled deuterated protein covering 220 K temperature range.
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Affiliation(s)
- Ümit Akbey
- Weizmann Institute of Science, Department of Chemical and Biological Physics, Perlman Chemical Sciences Building, P.O. Box 26, Rehovot 76100, Israel.
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10
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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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11
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Good DB, Voinov MA, Bolton D, Ward ME, Sergeyev IV, Caporini M, Scheffer P, Lo A, Rosay M, Marek A, Brown LS, I Smirnov A, Ladizhansky V. A biradical-tagged phospholipid as a polarizing agent for solid-state MAS Dynamic Nuclear Polarization NMR of membrane proteins. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 100:92-101. [PMID: 31029957 PMCID: PMC6709687 DOI: 10.1016/j.ssnmr.2019.04.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 03/29/2019] [Accepted: 04/12/2019] [Indexed: 06/01/2023]
Abstract
A novel Dynamic Nuclear Polarization (DNP) NMR polarizing agent ToSMTSL-PTE representing a phospholipid with a biradical TOTAPOL tethered to the polar head group has been synthesized, characterized, and employed to enhance solid-state Nuclear Magnetic Resonance (SSNMR) signal of a lipid-reconstituted integral membrane protein proteorhodopsin (PR). A matrix-free PR formulation for DNP improved the absolute sensitivity of NMR signal by a factor of ca. 4 compared to a conventional preparation with TOTAPOL dispersed in a glassy glycerol/water matrix. DNP enhancements measured at 400 MHz/263 GHz and 600 MHz/395 GHz showed a strong field dependence but remained moderate at both fields, and comparable to those obtained for PR covalently modified with ToSMTSL. Additional continuous wave (CW) X-band electron paramagnetic resonance (EPR) experiments with ToSMTSL-PTE in solutions and in lipid bilayers revealed that an unfavorable conformational change of the linker connecting mononitroxides could be one of the reasons for moderate DNP enhancements. Further, differential scanning calorimetry (DSC) and CW EPR experiments indicated an inhomogeneous distribution and/or a possibility of a partial aggregation of ToSMTSL-PTE in DMPC:DMPA bilayers when the concentration of the polarizing agent was increased to 20 mol% to maximize the DNP enhancement. Thus, conformational changes and an inhomogeneous distribution of the lipid-based biradicals in lipid bilayers emerged as important factors to consider for further development of this matrix-free approach for DNP of membrane proteins.
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Affiliation(s)
- Daryl B Good
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada
| | - Maxim A Voinov
- Department of Chemistry, North Carolina State University, Raleigh, NC, USA
| | - David Bolton
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada
| | - Meaghan E Ward
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada
| | | | | | - Peter Scheffer
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada
| | - Andy Lo
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada
| | | | - Antonin Marek
- Department of Chemistry, North Carolina State University, Raleigh, NC, USA
| | - Leonid S Brown
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada
| | - Alex I Smirnov
- Department of Chemistry, North Carolina State University, Raleigh, NC, USA; Bruker Biospin, Billerica, MA, USA.
| | - Vlad Ladizhansky
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada; Bruker Biospin, Billerica, MA, USA.
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12
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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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13
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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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14
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Lu M, Wang M, Sergeyev IV, Quinn CM, Struppe J, Rosay M, Maas W, Gronenborn AM, Polenova T. 19F Dynamic Nuclear Polarization at Fast Magic Angle Spinning for NMR of HIV-1 Capsid Protein Assemblies. J Am Chem Soc 2019; 141:5681-5691. [PMID: 30871317 PMCID: PMC6521953 DOI: 10.1021/jacs.8b09216] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We report remarkably high, up to 100-fold, signal enhancements in 19F dynamic nuclear polarization (DNP) magic angle spinning (MAS) spectra at 14.1 T on HIV-1 capsid protein (CA) assemblies. These enhancements correspond to absolute sensitivity ratios of 12-29 and are of similar magnitude to those seen for 1H signals in the same samples. At MAS frequencies above 20 kHz, it was possible to record 2D 19F-13C HETCOR spectra, which contain long-range intra- and intermolecular correlations. Such correlations provide unique distance restraints, inaccessible in conventional experiments without DNP, for protein structure determination. Furthermore, systematic quantification of the DNP enhancements as a function of biradical concentration, MAS frequency, temperature, and microwave power is reported. Our work establishes the power of DNP-enhanced 19F MAS NMR spectroscopy for structural characterization of HIV-1 CA assemblies, and this approach is anticipated to be applicable to a wide range of large biomolecular systems.
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Affiliation(s)
- Manman Lu
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Mingzhang Wang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Ivan V. Sergeyev
- Bruker Biospin Corporation, 15 Fortune Drive, Billerica, MA, United States
| | - Caitlin M. Quinn
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Jochem Struppe
- Bruker Biospin Corporation, 15 Fortune Drive, Billerica, MA, United States
| | - Melanie Rosay
- Bruker Biospin Corporation, 15 Fortune Drive, Billerica, MA, United States
| | - Werner Maas
- Bruker Biospin Corporation, 15 Fortune Drive, Billerica, MA, United States
| | - Angela M. Gronenborn
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
- Department of Structural Biology, University of Pittsburgh School of Medicine, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, PA 15261, United States
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15
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König A, Schölzel D, Uluca B, Viennet T, Akbey Ü, Heise H. Hyperpolarized MAS NMR of unfolded and misfolded proteins. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 98:1-11. [PMID: 30641444 DOI: 10.1016/j.ssnmr.2018.12.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 12/28/2018] [Accepted: 12/30/2018] [Indexed: 05/09/2023]
Abstract
In this article we give an overview over the use of DNP-enhanced solid-state NMR spectroscopy for the investigation of unfolded, disordered and misfolded proteins. We first provide an overview over studies in which DNP spectroscopy has successfully been applied for the structural investigation of well-folded amyloid fibrils formed by short peptides as well as full-length proteins. Sample cooling to cryogenic temperatures often leads to severe line broadening of resonance signals and thus a loss in resolution. However, inhomogeneous line broadening at low temperatures provides valuable information about residual dynamics and flexibility in proteins, and, in combination with appropriate selective isotope labeling techniques, inhomogeneous linewidths in disordered proteins or protein regions may be exploited for evaluation of conformational ensembles. In the last paragraph we highlight some recent studies where DNP-enhanced MAS-NMR-spectroscopy was applied to the study of disordered proteins/protein regions and inhomogeneous sample preparations.
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Affiliation(s)
- Anna König
- Institute of Complex Systems, Structural Biochemistry (ICS-6), Research Center Jülich, 52425, Jülich, Germany; Institute of Physical Biology, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Daniel Schölzel
- Institute of Complex Systems, Structural Biochemistry (ICS-6), Research Center Jülich, 52425, Jülich, Germany; Institute of Physical Biology, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Boran Uluca
- Institute of Complex Systems, Structural Biochemistry (ICS-6), Research Center Jülich, 52425, Jülich, Germany; Institute of Physical Biology, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Thibault Viennet
- Institute of Complex Systems, Structural Biochemistry (ICS-6), Research Center Jülich, 52425, Jülich, Germany; Institute of Physical Biology, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Ümit Akbey
- Institute of Complex Systems, Structural Biochemistry (ICS-6), Research Center Jülich, 52425, Jülich, Germany; Institute of Physical Biology, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Henrike Heise
- Institute of Complex Systems, Structural Biochemistry (ICS-6), Research Center Jülich, 52425, Jülich, Germany; Institute of Physical Biology, Heinrich-Heine-University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany.
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16
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Leavesley A, Jain S, Kamniker I, Zhang H, Rajca S, Rajca A, Han S. Maximizing NMR signal per unit time by facilitating the e-e-n cross effect DNP rate. Phys Chem Chem Phys 2018; 20:27646-27657. [PMID: 30375593 DOI: 10.1039/c8cp04909b] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The dynamic nuclear polarization (DNP) efficiency is critically dependent on the properties of the radical, solvent, and solute constituting the sample system. In this study, we focused on the three spin e-e-n cross effect (CE)'s influence on the nuclear longitudinal relaxation time constant T1n, the build-up time constants of nuclear magnetic resonance (NMR) signal, TDNP and DNP-enhancement of NMR signal. The dipolar interaction strength between the electron spins driving the e-e-n process was systematically modulated using mono-, di-, tri-, and dendritic-nitroxide radicals, while maintaining a constant global electron spin concentration of 10 mM. Experimental results showed that an increase in electron spin clustering led to an increased electron spin depolarization, as mapped by electron double resonance (ELDOR), and a dramatically shortened T1n and TDNP time constants under static and magic angle spinning (MAS) conditions. A theoretical analysis reveals that strong e-e interactions, caused by electron spin clustering, increase the CE rate. The three spin e-e-n CE is a hitherto little recognized mechanism for shortening T1n and TDNP in solid-state NMR experiments at cryogenic temperatures, and offers a design principle to enhance the effective CE DNP enhancement per unit time. Fast CE rates will benefit DNP at liquid helium temperatures, or at higher magnetic fields and pulsed DNP, where slow e-e-n polarization transfer rate is a key bottleneck to achieving maximal DNP performance.
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Affiliation(s)
- Alisa Leavesley
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA
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17
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Perras FA, Pruski M. Large-scale ab initio simulations of MAS DNP enhancements using a Monte Carlo optimization strategy. J Chem Phys 2018; 149:154202. [PMID: 30342444 DOI: 10.1063/1.5042651] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Magic-angle-spinning (MAS) dynamic nuclear polarization (DNP) has recently emerged as a powerful technology enabling otherwise unrealistic solid-state NMR experiments. The simulation of DNP processes which might, for example, aid in refining the experimental conditions or the design of better performing polarizing agents, is, however, plagued with significant challenges, often limiting the system size to only 3 spins. Here, we present the first approach to fully ab initio large-scale simulations of MAS DNP enhancements. The Landau-Zener equation is used to treat all interactions concerning electron spins, and the low-order correlations in the Liouville space method is used to accurately treat the spin diffusion, as well as its MAS speed dependence. As the propagator cannot be stored, a Monte Carlo optimization method is used to determine the steady-state enhancement factors. This new software is employed to investigate the MAS speed dependence of the enhancement factors in large spin systems where spin diffusion is of importance, as well as to investigate the impacts of solvent and polarizing agent deuteration on the performance of MAS DNP.
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18
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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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19
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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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20
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Scott FJ, Sesti EL, Choi EJ, Laut AJ, Sirigiri JR, Barnes AB. Magic angle spinning NMR with metallized rotors as cylindrical microwave resonators. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2018; 56:831-835. [PMID: 29672916 DOI: 10.1002/mrc.4744] [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: 01/25/2018] [Revised: 03/22/2018] [Accepted: 04/11/2018] [Indexed: 05/05/2023]
Abstract
We introduce a novel design for millimeter wave electromagnetic structures within magic angle spinning (MAS) rotors. In this demonstration, a copper coating is vacuum deposited onto the outside surface of a sapphire rotor at a thickness of 50 nm. This thickness is sufficient to reflect 197-GHz microwaves, yet not too thick as to interfere with radiofrequency fields at 300 MHz or prevent sample spinning due to eddy currents. Electromagnetic simulations of an idealized rotor geometry show a microwave quality factor of 148. MAS experiments with sample rotation frequencies of ωr /2π = 5.4 kHz demonstrate that the drag force due to eddy currents within the copper does not prevent sample spinning. Spectra of sodium acetate show resolved 13 C J-couplings of 60 Hz and no appreciable broadening between coated and uncoated sapphire rotors, demonstrating that the copper coating does not prevent shimming and high-resolution nuclear magnetic resonance spectroscopy. Additionally, 13 C Rabi nutation curves of ω1 /2π = 103 kHz for both coated and uncoated rotors indicate no detrimental impact of the copper coating on radio frequency coupling of the nuclear spins to the sample coil. We present this metal coated rotor as a first step towards an MAS resonator. MAS resonators are expected to have a significant impact on developments in electron decoupling, pulsed dynamic nuclear polarization (DNP), room temperature DNP, DNP with low-power microwave sources, and electron paramagnetic resonance detection.
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Affiliation(s)
- Faith J Scott
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO, 63130, USA
| | - Erika L Sesti
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO, 63130, USA
| | - Eric J Choi
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO, 63130, USA
| | - Alexander J Laut
- Bridge 12 Technologies, Inc., 37 Loring Drive, Framingham, MA, 01702, USA
| | | | - Alexander B Barnes
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO, 63130, USA
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21
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Zhao L, Pinon AC, Emsley L, Rossini AJ. DNP-enhanced solid-state NMR spectroscopy of active pharmaceutical ingredients. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2018; 56:583-609. [PMID: 29193278 DOI: 10.1002/mrc.4688] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 11/15/2017] [Accepted: 11/19/2017] [Indexed: 06/07/2023]
Abstract
Solid-state NMR spectroscopy has become a valuable tool for the characterization of both pure and formulated active pharmaceutical ingredients (APIs). However, NMR generally suffers from poor sensitivity that often restricts NMR experiments to nuclei with favorable properties, concentrated samples, and acquisition of one-dimensional (1D) NMR spectra. Here, we review how dynamic nuclear polarization (DNP) can be applied to routinely enhance the sensitivity of solid-state NMR experiments by one to two orders of magnitude for both pure and formulated APIs. Sample preparation protocols for relayed DNP experiments and experiments on directly doped APIs are detailed. Numerical spin diffusion models illustrate the dependence of relayed DNP enhancements on the relaxation properties and particle size of the solids and can be used for particle size determination when the other factors are known. We then describe the advanced solid-state NMR experiments that have been enabled by DNP and how they provide unique insight into the molecular and macroscopic structure of APIs. For example, with large sensitivity gains provided by DNP, natural isotopic abundance, 13 C-13 C double-quantum single-quantum homonuclear correlation NMR spectra of pure APIs can be routinely acquired. DNP also enables solid-state NMR experiments with unreceptive quadrupolar nuclei such as 2 H, 14 N, and 35 Cl that are commonly found in APIs. Applications of DNP-enhanced solid-state NMR spectroscopy for the molecular level characterization of low API load formulations such as commercial tablets and amorphous solid dispersions are described. Future perspectives for DNP-enhanced solid-state NMR experiments on APIs are briefly discussed.
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Affiliation(s)
- Li Zhao
- Department of Chemistry, Iowa State University, Ames, IA, USA
- US DOE Ames Laboratory, Ames, IA, USA
| | - Arthur C Pinon
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Lyndon Emsley
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Aaron J Rossini
- Department of Chemistry, Iowa State University, Ames, IA, USA
- US DOE Ames Laboratory, Ames, IA, USA
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22
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Ni QZ, Can TV, Daviso E, Belenky M, Griffin RG, Herzfeld J. Primary Transfer Step in the Light-Driven Ion Pump Bacteriorhodopsin: An Irreversible U-Turn Revealed by Dynamic Nuclear Polarization-Enhanced Magic Angle Spinning NMR. J Am Chem Soc 2018; 140:4085-4091. [PMID: 29489362 DOI: 10.1021/jacs.8b00022] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite much attention, the path of the highly consequential primary proton transfer in the light-driven ion pump bacteriorhodopsin (bR) remains mysterious. Here we use DNP-enhanced magic angle spinning (MAS) NMR to study critical elements of the active site just before the Schiff base (SB) deprotonates (in the L intermediate), immediately after the SB has deprotonated and Asp85 has become protonated (in the Mo intermediate), and just after the SB has reprotonated and Asp96 has deprotonated (in the N intermediate). An essential feature that made these experiments possible is the 75-fold signal enhancement through DNP. 15N(SB)-1H correlations reveal that the newly deprotonated SB is accepting a hydrogen bond from an alcohol and 13C-13C correlations show that Asp85 draws close to Thr89 before the primary proton transfer. Concurrently, 15N-13C correlations between the SB and Asp85 show that helices C and G draw closer together just prior to the proton transfer and relax thereafter. Together, these results indicate that Thr89 serves to relay the SB proton to Asp85 and that creating this pathway involves rapprochement between the C and G helices as well as chromophore torsion.
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Affiliation(s)
- Qing Zhe Ni
- Department of Chemistry and Francis Bitter Magnet Laboratory , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , Massachusetts 02139 , United States
| | - Thach V Can
- Department of Chemistry and Francis Bitter Magnet Laboratory , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , Massachusetts 02139 , United States
| | - Eugenio Daviso
- Department of Chemistry and Francis Bitter Magnet Laboratory , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , Massachusetts 02139 , United States.,Department of Chemistry , Brandeis University , Waltham , Massachusetts 02454 , United States
| | - Marina Belenky
- Department of Chemistry , Brandeis University , Waltham , Massachusetts 02454 , United States
| | - Robert G Griffin
- Department of Chemistry and Francis Bitter Magnet Laboratory , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , Massachusetts 02139 , United States
| | - Judith Herzfeld
- Department of Chemistry , Brandeis University , Waltham , Massachusetts 02454 , United States
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23
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Lilly Thankamony AS, Wittmann JJ, Kaushik M, Corzilius B. Dynamic nuclear polarization for sensitivity enhancement in modern solid-state NMR. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2017; 102-103:120-195. [PMID: 29157490 DOI: 10.1016/j.pnmrs.2017.06.002] [Citation(s) in RCA: 263] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 06/03/2017] [Accepted: 06/08/2017] [Indexed: 05/03/2023]
Abstract
The field of dynamic nuclear polarization has undergone tremendous developments and diversification since its inception more than 6 decades ago. In this review we provide an in-depth overview of the relevant topics involved in DNP-enhanced MAS NMR spectroscopy. This includes the theoretical description of DNP mechanisms as well as of the polarization transfer pathways that can lead to a uniform or selective spreading of polarization between nuclear spins. Furthermore, we cover historical and state-of-the art aspects of dedicated instrumentation, polarizing agents, and optimization techniques for efficient MAS DNP. Finally, we present an extensive overview on applications in the fields of structural biology and materials science, which underlines that MAS DNP has moved far beyond the proof-of-concept stage and has become an important tool for research in these fields.
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Affiliation(s)
- Aany Sofia Lilly Thankamony
- Institute of Physical and Theoretical Chemistry, Institute of Biophysical Chemistry, and Center for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
| | - Johannes J Wittmann
- Institute of Physical and Theoretical Chemistry, Institute of Biophysical Chemistry, and Center for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
| | - Monu Kaushik
- Institute of Physical and Theoretical Chemistry, Institute of Biophysical Chemistry, and Center for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany
| | - Björn Corzilius
- Institute of Physical and Theoretical Chemistry, Institute of Biophysical Chemistry, and Center for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt, Germany.
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24
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Li C, Zhao J, Cheng K, Ge Y, Wu Q, Ye Y, Xu G, Zhang Z, Zheng W, Zhang X, Zhou X, Pielak G, Liu M. Magnetic Resonance Spectroscopy as a Tool for Assessing Macromolecular Structure and Function in Living Cells. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2017; 10:157-182. [PMID: 28301750 DOI: 10.1146/annurev-anchem-061516-045237] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Investigating the structure, modification, interaction, and function of biomolecules in their native cellular environment leads to physiologically relevant knowledge about their mechanisms, which will benefit drug discovery and design. In recent years, nuclear and electron magnetic resonance (NMR) spectroscopy has emerged as a useful tool for elucidating the structure and function of biomacromolecules, including proteins, nucleic acids, and carbohydrates in living cells at atomic resolution. In this review, we summarize the progress and future of in-cell NMR as it is applied to proteins, nucleic acids, and carbohydrates.
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Affiliation(s)
- Conggang Li
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Jiajing Zhao
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Kai Cheng
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Yuwei Ge
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Qiong Wu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Yansheng Ye
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Guohua Xu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Zeting Zhang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Wenwen Zheng
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Xu Zhang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Xin Zhou
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
| | - Gary Pielak
- Department of Chemistry, Department of Biochemistry and Biophysics, and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Maili Liu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; ,
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25
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Saliba EP, Sesti EL, Scott FJ, Albert BJ, Choi EJ, Alaniva N, Gao C, Barnes AB. Electron Decoupling with Dynamic Nuclear Polarization in Rotating Solids. J Am Chem Soc 2017; 139:6310-6313. [DOI: 10.1021/jacs.7b02714] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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
| | - Faith J. Scott
- 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
| | - Eric J. Choi
- 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
| | - Chukun Gao
- 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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26
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Rogawski R, Sergeyev IV, Li Y, Ottaviani MF, Cornish V, McDermott AE. Dynamic Nuclear Polarization Signal Enhancement with High-Affinity Biradical Tags. J Phys Chem B 2017; 121:1169-1175. [PMID: 28099013 DOI: 10.1021/acs.jpcb.6b09021] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Dynamic nuclear polarization is an emerging technique for sensitizing solid-state NMR experiments by transferring polarization from electrons to nuclei. Stable biradicals, the polarization source for the cross effect mechanism, are typically codissolved at millimolar concentrations with proteins of interest. Here we describe the high-affinity biradical tag TMP-T, created by covalently linking trimethoprim, a nanomolar affinity ligand of dihydrofolate reductase (DHFR), to the biradical polarizing agent TOTAPOL. With TMP-T bound to DHFR, large enhancements of the protein spectrum are observed, comparable to when TOTAPOL is codissolved with the protein. In contrast to TOTAPOL, the tight binding TMP-T can be added stoichiometrically at radical concentrations orders of magnitude lower than in previously described preparations. Benefits of the reduced radical concentration include reduced spectral bleaching, reduced chemical perturbation of the sample, and the ability to selectively enhance signals for the protein of interest.
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Affiliation(s)
- Rivkah Rogawski
- Department of Chemistry, Columbia University , New York, New York 10027, United States
| | - Ivan V Sergeyev
- Department of Chemistry, Columbia University , New York, New York 10027, United States
| | - Yongjun Li
- Department of Chemistry, Columbia University , New York, New York 10027, United States
| | - M Francesca Ottaviani
- Department of Pure and Applied Sciences, University of Urbino , Loc. Crocicchia, 61029 Urbino, Italy
| | - Virginia Cornish
- Department of Chemistry, Columbia University , New York, New York 10027, United States
| | - Ann E McDermott
- Department of Chemistry, Columbia University , New York, New York 10027, United States
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27
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Daube D, Aladin V, Heiliger J, Wittmann JJ, Barthelmes D, Bengs C, Schwalbe H, Corzilius B. Heteronuclear Cross-Relaxation under Solid-State Dynamic Nuclear Polarization. J Am Chem Soc 2016; 138:16572-16575. [DOI: 10.1021/jacs.6b08683] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Diane Daube
- Institute
of Physical and Theoretical Chemistry and Institute of Biophysical
Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt am Main, Germany
- Center
for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - Victoria Aladin
- Institute
of Physical and Theoretical Chemistry and Institute of Biophysical
Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt am Main, Germany
- Center
for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - Jörg Heiliger
- Institute
of Physical and Theoretical Chemistry and Institute of Biophysical
Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt am Main, Germany
- Center
for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - Johannes J. Wittmann
- Institute
of Physical and Theoretical Chemistry and Institute of Biophysical
Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt am Main, Germany
- Center
for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - Dominic Barthelmes
- Center
for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
- Institute
of Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Germany
| | - Christian Bengs
- Institute
of Physical and Theoretical Chemistry and Institute of Biophysical
Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt am Main, Germany
- Center
for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - Harald Schwalbe
- Center
for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
- Institute
of Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt am Main, Germany
| | - Björn Corzilius
- Institute
of Physical and Theoretical Chemistry and Institute of Biophysical
Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt am Main, Germany
- Center
for Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
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28
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Kaushik M, Bahrenberg T, Can TV, Caporini MA, Silvers R, Heiliger J, Smith AA, Schwalbe H, Griffin RG, Corzilius B. Gd(iii) and Mn(ii) complexes for dynamic nuclear polarization: small molecular chelate polarizing agents and applications with site-directed spin labeling of proteins. Phys Chem Chem Phys 2016; 18:27205-27218. [PMID: 27545112 PMCID: PMC5053914 DOI: 10.1039/c6cp04623a] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigate complexes of two paramagnetic metal ions Gd3+ and Mn2+ to serve as polarizing agents for solid-state dynamic nuclear polarization (DNP) of 1H, 13C, and 15N at magnetic fields of 5, 9.4, and 14.1 T. Both ions are half-integer high-spin systems with a zero-field splitting and therefore exhibit a broadening of the mS = -1/2 ↔ +1/2 central transition which scales inversely with the external field strength. We investigate experimentally the influence of the chelator molecule, strong hyperfine coupling to the metal nucleus, and deuteration of the bulk matrix on DNP properties. At small Gd-DOTA concentrations the narrow central transition allows us to polarize nuclei with small gyromagnetic ratio such as 13C and even 15N via the solid effect. We demonstrate that enhancements observed are limited by the available microwave power and that large enhancement factors of >100 (for 1H) and on the order of 1000 (for 13C) can be achieved in the saturation limit even at 80 K. At larger Gd(iii) concentrations (≥10 mM) where dipolar couplings between two neighboring Gd3+ complexes become substantial a transition towards cross effect as dominating DNP mechanism is observed. Furthermore, the slow spin-diffusion between 13C and 15N, respectively, allows for temporally resolved observation of enhanced polarization spreading from nuclei close to the paramagnetic ion towards nuclei further removed. Subsequently, we present preliminary DNP experiments on ubiquitin by site-directed spin-labeling with Gd3+ chelator tags. The results hold promise towards applications of such paramagnetically labeled proteins for DNP applications in biophysical chemistry and/or structural biology.
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Affiliation(s)
- Monu Kaushik
- Institute of Physical and Theoretical Chemistry and Institute of Biophysical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7-9, 60438 Frankfurt am Main, Germany.
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29
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Akbey Ü, Oschkinat H. Structural biology applications of solid state MAS DNP NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 269:213-224. [PMID: 27095695 DOI: 10.1016/j.jmr.2016.04.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 04/05/2016] [Accepted: 04/05/2016] [Indexed: 06/05/2023]
Abstract
Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance.
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Affiliation(s)
- Ümit Akbey
- Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Høegh-Guldbergs Gade 6B, 8000 Aarhus C, Denmark; Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark.
| | - Hartmut Oschkinat
- Leibniz Institute für Molekulare Pharmakologie (FMP), NMR Supported Structural Biology, Robert Roessle Str. 10, 13125 Berlin, Germany.
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30
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Lelli M, Chaudhari SR, Gajan D, Casano G, Rossini AJ, Ouari O, Tordo P, Lesage A, Emsley L. Solid-State Dynamic Nuclear Polarization at 9.4 and 18.8 T from 100 K to Room Temperature. J Am Chem Soc 2015; 137:14558-61. [PMID: 26555676 PMCID: PMC4671100 DOI: 10.1021/jacs.5b08423] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Efficient dynamic nuclear polarization
(DNP) in solids, which enables
very high sensitivity NMR experiments, is currently limited to temperatures
of around 100 K and below. Here we show how by choosing an adequate
solvent, 1H cross effect DNP enhancements of over 80 can
be obtained at 240 K. To achieve this we use the biradical TEKPol
dissolved in a glassy phase of ortho-terphenyl (OTP).
We study the solvent DNP enhancement of both TEKPol and BDPA in OTP
in the range from 100 to 300 K at 9.4 and 18.8 T. Surprisingly, we
find that the DNP enhancement decreases only relatively slowly for
temperatures below the glass transition of OTP (Tg = 243 K), and 1H enhancements around 15–20
at ambient temperature can be observed. We use this to monitor molecular
dynamic transitions in the pharmaceutically relevant solids Ambroxol
and Ibuprofen.
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Affiliation(s)
- Moreno Lelli
- Institut de Sciences Analytiques, Centre de RMN à Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) , 69100 Villeurbanne, France
| | - Sachin R Chaudhari
- Institut de Sciences Analytiques, Centre de RMN à Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) , 69100 Villeurbanne, France
| | - David Gajan
- Institut de Sciences Analytiques, Centre de RMN à Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) , 69100 Villeurbanne, France
| | - Gilles Casano
- Aix-Marseille Université, CNRS, ICR UMR 7273 , 13397 Marseille, France
| | - Aaron J Rossini
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Olivier Ouari
- Aix-Marseille Université, CNRS, ICR UMR 7273 , 13397 Marseille, France
| | - Paul Tordo
- Aix-Marseille Université, CNRS, ICR UMR 7273 , 13397 Marseille, France
| | - Anne Lesage
- Institut de Sciences Analytiques, Centre de RMN à Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) , 69100 Villeurbanne, France
| | - Lyndon Emsley
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
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31
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Matsuki Y, Nakamura S, Fukui S, Suematsu H, Fujiwara T. Closed-cycle cold helium magic-angle spinning for sensitivity-enhanced multi-dimensional solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 259:76-81. [PMID: 26302269 DOI: 10.1016/j.jmr.2015.08.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 08/04/2015] [Indexed: 05/21/2023]
Abstract
Magic-angle spinning (MAS) NMR is a powerful tool for studying molecular structure and dynamics, but suffers from its low sensitivity. Here, we developed a novel helium-cooling MAS NMR probe system adopting a closed-loop gas recirculation mechanism. In addition to the sensitivity gain due to low temperature, the present system has enabled highly stable MAS (vR=4-12 kHz) at cryogenic temperatures (T=35-120 K) for over a week without consuming helium at a cost for electricity of 16 kW/h. High-resolution 1D and 2D data were recorded for a crystalline tri-peptide sample at T=40 K and B0=16.4 T, where an order of magnitude of sensitivity gain was demonstrated versus room temperature measurement. The low-cost and long-term stable MAS strongly promotes broader application of the brute-force sensitivity-enhanced multi-dimensional MAS NMR, as well as dynamic nuclear polarization (DNP)-enhanced NMR in a temperature range lower than 100 K.
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Affiliation(s)
- Yoh Matsuki
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Shinji Nakamura
- JEOL RESONANCE Inc., 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan
| | - Shigeo Fukui
- Cryovac Corporation, 2-12-14 Chibune, Nishi Yodogawa, Osaka 555-0013, Japan
| | - Hiroto Suematsu
- JEOL RESONANCE Inc., 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan
| | - Toshimichi Fujiwara
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
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32
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Voinov MA, Good DB, Ward ME, Milikisiyants S, Marek A, Caporini MA, Rosay M, Munro RA, Ljumovic M, Brown LS, Ladizhansky V, Smirnov AI. Cysteine-Specific Labeling of Proteins with a Nitroxide Biradical for Dynamic Nuclear Polarization NMR. J Phys Chem B 2015; 119:10180-90. [DOI: 10.1021/acs.jpcb.5b05230] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Maxim A. Voinov
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | | | | | - Sergey Milikisiyants
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Antonin Marek
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Marc A. Caporini
- Bruker Biospin Ltd., Billerica, Massachusetts 01821, United States
| | - Melanie Rosay
- Bruker Biospin Ltd., Billerica, Massachusetts 01821, United States
| | | | | | | | | | - Alex I. Smirnov
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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33
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van der Cruijsen EAW, Koers EJ, Sauvée C, Hulse RE, Weingarth M, Ouari O, Perozo E, Tordo P, Baldus M. Biomolecular DNP-Supported NMR Spectroscopy using Site-Directed Spin Labeling. Chemistry 2015; 21:12971-7. [DOI: 10.1002/chem.201501376] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Indexed: 12/24/2022]
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34
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Lewandowski JR, Halse ME, Blackledge M, Emsley L. Direct observation of hierarchical protein dynamics. Science 2015; 348:578-81. [DOI: 10.1126/science.aaa6111] [Citation(s) in RCA: 183] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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35
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Can TV, Ni QZ, Griffin RG. Mechanisms of dynamic nuclear polarization in insulating solids. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 253:23-35. [PMID: 25797002 PMCID: PMC4371145 DOI: 10.1016/j.jmr.2015.02.005] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 02/05/2015] [Accepted: 02/09/2015] [Indexed: 05/04/2023]
Abstract
Dynamic nuclear polarization (DNP) is a technique used to enhance signal intensities in NMR experiments by transferring the high polarization of electrons to their surrounding nuclei. The past decade has witnessed a renaissance in the development of DNP, especially at high magnetic fields, and its application in several areas including biophysics, chemistry, structural biology and materials science. Recent technical and theoretical advances have expanded our understanding of established experiments: for example, the cross effect DNP in samples spinning at the magic angle. Furthermore, new experiments suggest that our understanding of the Overhauser effect and its applicability to insulating solids needs to be re-examined. In this article, we summarize important results of the past few years and provide quantum mechanical explanations underlying these results. We also discuss future directions of DNP and current limitations, including the problem of resolution in protein spectra recorded at 80-100 K.
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Affiliation(s)
- T V Can
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Q Z Ni
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - R G Griffin
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
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Su Y, Andreas L, Griffin RG. Magic angle spinning NMR of proteins: high-frequency dynamic nuclear polarization and (1)H detection. Annu Rev Biochem 2015; 84:465-97. [PMID: 25839340 DOI: 10.1146/annurev-biochem-060614-034206] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Magic angle spinning (MAS) NMR studies of amyloid and membrane proteins and large macromolecular complexes are an important new approach to structural biology. However, the applicability of these experiments, which are based on (13)C- and (15)N-detected spectra, would be enhanced if the sensitivity were improved. Here we discuss two advances that address this problem: high-frequency dynamic nuclear polarization (DNP) and (1)H-detected MAS techniques. DNP is a sensitivity enhancement technique that transfers the high polarization of exogenous unpaired electrons to nuclear spins via microwave irradiation of electron-nuclear transitions. DNP boosts NMR signal intensities by factors of 10(2) to 10(3), thereby overcoming NMR's inherent low sensitivity. Alternatively, it permits structural investigations at the nanomolar scale. In addition, (1)H detection is feasible primarily because of the development of MAS rotors that spin at frequencies of 40 to 60 kHz or higher and the preparation of extensively (2)H-labeled proteins.
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Affiliation(s)
- Yongchao Su
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139;
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37
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Markin AV, Markhasin E, Sologubov SS, Ni QZ, Smirnova NN, Griffin RG. Low-temperature polymorphic phase transition in a crystalline tripeptide L-Ala-L-Pro-Gly·H2O revealed by adiabatic calorimetry. J Phys Chem B 2015; 119:1787-92. [PMID: 25588051 DOI: 10.1021/jp508710g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We demonstrate application of precise adiabatic vacuum calorimetry to observation of phase transition in the tripeptide L-alanyl-L-prolyl-glycine monohydrate (APG) from 6 to 320 K and report the standard thermodynamic properties of the tripeptide in the entire range. Thus, the heat capacity of APG was measured by adiabatic vacuum calorimetry in the above temperature range. The tripeptide exhibits a reversible first-order solid-to-solid phase transition characterized by strong thermal hysteresis. We report the standard thermodynamic characteristics of this transition and show that differential scanning calorimetry can reliably characterize the observed phase transition with <5 mg of the sample. Additionally, the standard entropy of formation from the elemental substances and the standard entropy of hypothetical reaction of synthesis from the amino acids at 298.15 K were calculated for the studied tripeptide.
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Affiliation(s)
- Alexey V Markin
- Lobachevsky State University of Nizhny Novgorod , Gagarin Pr. 23/5, Nizhny Novgorod 603950, Russia
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38
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Cellular solid-state NMR investigation of a membrane protein using dynamic nuclear polarization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:342-9. [PMID: 25017802 DOI: 10.1016/j.bbamem.2014.07.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 06/30/2014] [Accepted: 07/02/2014] [Indexed: 12/16/2022]
Abstract
While an increasing number of structural biology studies successfully demonstrate the power of high-resolution structures and dynamics of membrane proteins in fully understanding their function, there is considerable interest in developing NMR approaches to obtain such information in a cellular setting. As long as the proteins inside the living cell tumble rapidly in the NMR timescale, recently developed in-cell solution NMR approaches can provide 3D structural information. However, there are numerous challenges to study membrane proteins inside a cell. Research in our laboratory is focused on developing a combination of solid-state NMR and biological approaches to overcome these challenges in order to obtain high-resolution structural insights into electron transfer processes mediated by membrane-bound proteins like mammalian cytochrome-b5, cytochrome-P450 and cytochrome-P450-reductase. In this study, we demonstrate the feasibility of using dynamic nuclear polarization (DNP) magic angle spinning (MAS) NMR spectroscopy for in-cell studies on a membrane-anchored protein. Our experimental results obtained from ¹³C-labeled membrane-anchored cytochrome-b5 in native Escherichia coli cells show a ~16-fold DNP signal enhancement. Further, results obtained from a 2D ¹³C/¹³C chemical shift correlation MAS experiment demonstrate the feasibility of suppressing the background signals from other cellular contents for high-resolution structural studies on membrane proteins. We believe that this study would pave new avenues for high-resolution structural studies on a variety of membrane-associated proteins and their complexes in the cellular context to fully understand their functional roles in physiological processes.
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Slichter CP. The discovery and renaissance of dynamic nuclear polarization. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2014; 77:072501. [PMID: 24994709 DOI: 10.1088/0034-4885/77/7/072501] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In 1952, Overhauser proposed a method for transferring the large electron spin polarization of conduction electrons in a metal to the metal nuclei, enhancing their polarization one thousand fold. Such an enhancement method is called dynamic nuclear polarization (DNP). The article explains his idea, describes the experiments of Carver and Slichter that confirmed his proposal, their demonstration that the method was not limited to metals, describes the nature of immediate impact on the magnetic resonance community, discusses why DNP was not broadly utilized for many years, explains in simple terms how the method works and reports on the new developments in experimental methods that have given DNP an active and exciting future.
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Affiliation(s)
- Charles P Slichter
- Department of Physics, University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA
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40
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Walker SA, Edwards DT, Siaw TA, Armstrong BD, Han S. Temperature dependence of high field 13C dynamic nuclear polarization processes with trityl radicals below 35 Kelvin. Phys Chem Chem Phys 2014; 15:15106-20. [PMID: 23925724 DOI: 10.1039/c3cp51628h] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In order to facilitate versatile applications with high field dynamic nuclear polarization (DNP), it is important to be able to optimize the DNP performance, i.e. reach high nuclear hyperpolarization within a short signal build up time. Given that the solid-state DNP process is strongly temperature-dependent, it is important to benchmark the temperature dependence of various DNP and electron paramagnetic resonance (EPR) parameters that can then be used to test and develop theories and models for high field DNP mechanisms. However, DNP and EPR experiments at high fields and cryogenic temperatures below 20 Kelvin usually require home built instrumentation, and therefore even basic experimental observations are lacking in the literature. DNP and EPR experiments at 7 T (197 GHz) and 8.5 T (240 GHz), respectively, were conducted at temperatures between 35 K and 3.7 K where the electron thermal polarization changes from 13.4% to 85.6%, respectively. The samples are frozen solutions of 15 mM OX063Me trityl radicals in various mixtures of [1-(13)C]pyruvic acid, glycerol, and Gd(3+)-chelates. For all sample mixtures, the trityl EPR lines are found to be inhomogeneously broadened and the dominant DNP mechanism is shown to be the cross effect (CE). A 20%, 11%, and 6.77% (13)C polarization is achieved at 3.7 K with a [1-(13)C]pyruvic-glycerol-H2O sample, the addition of 2 mM of Gd(3+)-chelates, and pure [1-(13)C]pyruvic acid, respectively. When T1n is sufficiently long, our results seem to suggest T1e is a key variable in the DNP process, where longer T1e values correlate with larger DNP enhancements (εDNP). The experimental data reported here on the temperature dependence of T1n, T1e, Tm (electron phase memory time), the EPR linewidth, TDNP and ε(DNP) at high fields will be helpful for testing the mechanism and theory of DNP processes.
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Affiliation(s)
- Shamon A Walker
- Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, CA 93106, USA
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41
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Corzilius B, Andreas LB, Smith AA, Ni QZ, Griffin RG. Paramagnet induced signal quenching in MAS-DNP experiments in frozen homogeneous solutions. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 240:113-23. [PMID: 24394190 PMCID: PMC3951579 DOI: 10.1016/j.jmr.2013.11.013] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 11/21/2013] [Accepted: 11/22/2013] [Indexed: 05/06/2023]
Abstract
The effects of nuclear signal quenching induced by the presence of a paramagnetic polarizing agent are documented for conditions used in magic angle spinning (MAS)-dynamic nuclear polarization (DNP) experiments on homogeneous solutions. In particular, we present a detailed analysis of three time constants: (1) the longitudinal build-up time constant TB for (1)H; (2) the rotating frame relaxation time constant T1ρ for (1)H and (13)C and (3) T2 of (13)C, the transverse relaxation time constant in the laboratory frame. These relaxation times were measured during microwave irradiation at a magnetic field of 5 T (140 GHz) as a function of the concentration of four polarizing agents: TOTAPOL, 4-amino-TEMPO, trityl (OX063), and Gd-DOTA and are compared to those obtained for a sample lacking paramagnetic doping. We also report the EPR relaxation time constants T1S and T2S, the DNP enhancements, ε, and the parameter E, defined below, which measures the sensitivity enhancement for the four polarizing agents as a function of the electron concentration. We observe substantial intensity losses (paramagnetic quenching) with all of the polarizing agents due to broadening mechanisms and cross relaxation during MAS. In particular, the monoradical trityl and biradical TOTAPOL induce ∼40% and 50% loss of signal intensity. In contrast there is little suppression of signal intensity in static samples containing these paramagnetic species. Despite the losses due to quenching, we find that all of the polarizing agents provide substantial gains in signal intensity with DNP, and in particular that the net enhancement is optimal for biradicals that operate with the cross effect. We discuss the possibility that much of this polarization loss can be regained with the development of instrumentation and methods to perform electron decoupling.
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Affiliation(s)
- Björn Corzilius
- Francis Bitter Magnet Laboratory, Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Loren B Andreas
- Francis Bitter Magnet Laboratory, Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Albert A Smith
- Francis Bitter Magnet Laboratory, Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Qing Zhe Ni
- Francis Bitter Magnet Laboratory, Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Robert G Griffin
- Francis Bitter Magnet Laboratory, Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
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42
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Michaelis VK, Ong TC, Kiesewetter MK, Frantz DK, Walish JJ, Ravera E, Luchinat C, Swager TM, Griffin RG. Topical Developments in High-Field Dynamic Nuclear Polarization. Isr J Chem 2014; 54:207-221. [PMID: 25977588 DOI: 10.1002/ijch.201300126] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We report our recent efforts directed at improving high-field DNP experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from ε = 25 to 82 that demonstrate the impact of molecular structure on performance. We directly polarized low-gamma nuclei including 13C, 2H, and 17O using trityl via the cross effect. We discuss a variety of sample preparation techniques for DNP with emphasis on the benefit of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700 MHz / 460 GHz DNP system that improves microwave delivery and increases enhancements up to 50%.
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Affiliation(s)
- Vladimir K Michaelis
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.,Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
| | - Ta-Chung Ong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.,Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
| | - Matthew K Kiesewetter
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
| | - Derik K Frantz
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
| | - Joseph J Walish
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
| | - Enrico Ravera
- Department of Chemistry "Ugo Schiff" and Magnetic Resonance Center (CERM) University of Florence, 50019 Sesto Fiorentino (FI), Italy
| | - Claudio Luchinat
- Department of Chemistry "Ugo Schiff" and Magnetic Resonance Center (CERM) University of Florence, 50019 Sesto Fiorentino (FI), Italy
| | - Timothy M Swager
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
| | - Robert G Griffin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.,Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA
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43
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Concistrè M, Carignani E, Borsacchi S, Johannessen OG, Mennucci B, Yang Y, Geppi M, Levitt MH. Freezing of Molecular Motions Probed by Cryogenic Magic Angle Spinning NMR. J Phys Chem Lett 2014; 5:512-516. [PMID: 26276602 DOI: 10.1021/jz4026276] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Cryogenic magic angle spinning makes it possible to obtain the NMR spectra of solids at temperatures low enough to freeze out most molecular motions. We have applied cryogenic magic angle spinning NMR to a crystalline small-molecule solid (ibuprofen sodium salt), which displays a variety of molecular dynamics. Magic angle (13)C NMR spectra are shown for a wide range of temperatures, including in the cryogenic regime down to 20 K. The hydrophobic and hydrophilic regions of the molecular structure display different behavior in the cryogenic regime, with the hydrophilic region remaining well-structured, while the hydrophobic region exhibits a broad frozen conformational distribution.
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Affiliation(s)
- Maria Concistrè
- †School of Chemistry, University of Southampton, SO17 1BJ Southampton, United Kingdom
| | - Elisa Carignani
- ‡Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy
| | - Silvia Borsacchi
- ‡Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy
| | - Ole G Johannessen
- †School of Chemistry, University of Southampton, SO17 1BJ Southampton, United Kingdom
| | - Benedetta Mennucci
- ‡Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy
| | - Yifeng Yang
- §School of Engineering Science, University of Southampton, Southampton, United Kingdom
| | - Marco Geppi
- ‡Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy
| | - Malcolm H Levitt
- †School of Chemistry, University of Southampton, SO17 1BJ Southampton, United Kingdom
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44
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Takahashi H, Fernández-de-Alba C, Lee D, Maurel V, Gambarelli S, Bardet M, Hediger S, Barra AL, De Paëpe G. Optimization of an absolute sensitivity in a glassy matrix during DNP-enhanced multidimensional solid-state NMR experiments. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 239:91-99. [PMID: 24480716 DOI: 10.1016/j.jmr.2013.12.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 12/03/2013] [Accepted: 12/09/2013] [Indexed: 06/03/2023]
Abstract
Thanks to instrumental and theoretical development, notably the access to high-power and high-frequency microwave sources, high-field dynamic nuclear polarization (DNP) on solid-state NMR currently appears as a promising solution to enhance nuclear magnetization in many different types of systems. In magic-angle-spinning DNP experiments, systems of interest are usually dissolved or suspended in glass-forming matrices doped with polarizing agents and measured at low temperature (down to ∼100K). In this work, we discuss the influence of sample conditions (radical concentration, sample temperature, etc.) on DNP enhancements and various nuclear relaxation times which affect the absolute sensitivity of DNP spectra, especially in multidimensional experiments. Furthermore, DNP-enhanced solid-state NMR experiments performed at 9.4 T are complemented by high-field CW EPR measurements performed at the same magnetic field. Microwave absorption by the DNP glassy matrix is observed even below the glass transition temperature caused by softening of the glass. Shortening of electron relaxation times due to glass softening and its impact in terms of DNP sensitivity is discussed.
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Affiliation(s)
- Hiroki Takahashi
- Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France
| | - Carlos Fernández-de-Alba
- Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France
| | - Daniel Lee
- Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France
| | - Vincent Maurel
- Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France
| | - Serge Gambarelli
- Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France
| | - Michel Bardet
- Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France
| | - Sabine Hediger
- Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France
| | - Anne-Laure Barra
- Laboratoire National des Champs Magnétiques Intenses, CNRS, F-38042 Grenoble, France
| | - Gaël De Paëpe
- Laboratoire de Chimie Inorganique et Biologique, UMR-E3 (CEA/UJF) and CNRS, Institut Nanosciences et Cryogénie, CEA, 38054 Grenoble, France.
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45
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ConcistrÈ M, Johannessen OG, Carignani E, Geppi M, Levitt MH. Magic-angle spinning NMR of cold samples. Acc Chem Res 2013; 46:1914-22. [PMID: 23488538 DOI: 10.1021/ar300323c] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Magic-angle-spinning solid-state NMR provides site-resolved structural and chemical information about molecules that complements many other physical techniques. Recent technical advances have made it possible to perform magic-angle-spinning NMR experiments at low temperatures, allowing researchers to trap reaction intermediates and to perform site-resolved studies of low-temperature physical phenomena such as quantum rotations, quantum tunneling, ortho-para conversion between spin isomers, and superconductivity. In examining biological molecules, the improved sensitivity provided by cryogenic NMR facilitates the study of protein assembly or membrane proteins. The combination of low-temperatures with dynamic nuclear polarization has the potential to boost sensitivity even further. Many research groups, including ours, have addressed the technical challenges and developed hardware for magic-angle-spinning of samples cooled down to a few tens of degrees Kelvin. In this Account, we briefly describe these hardware developments and review several recent activities of our group which involve low-temperature magic-angle-spinning NMR. Low-temperature operation allows us to trap intermediates that cannot be studied under ambient conditions by NMR because of their short lifetime. We have used low-temperature NMR to study the electronic structure of bathorhodopsin, the primary photoproduct of the light-sensitive membrane protein, rhodopsin. This project used a custom-built NMR probe that allows low-temperature NMR in the presence of illumination (the image shows the illuminated spinner module). We have also used this technique to study the behavior of molecules within a restricted environment. Small-molecule endofullerenes are interesting molecular systems in which molecular rotors are confined to a well-insulated, well-defined, and highly symmetric environment. We discuss how cryogenic solid state NMR can give information on the dynamics of ortho-water confined in a fullerene cage. Molecular motions are often connected with fundamental chemical properties; therefore, an understanding of molecular dynamics can be important in fields ranging from material science to biochemistry. We present the case of ibuprofen sodium salt which exhibits different degrees of conformational freedom in different parts of the same molecule, leading to a range of line broadening and line narrowing phenomena as a function of temperature.
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Affiliation(s)
- Maria ConcistrÈ
- School of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom
| | - Ole G. Johannessen
- School of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom
| | - Elisa Carignani
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126, Pisa, Italy
| | - Marco Geppi
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126, Pisa, Italy
| | - Malcolm H. Levitt
- School of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom
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46
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Ni QZ, Daviso E, Can TV, Markhasin E, Jawla SK, Swager TM, Temkin RJ, Herzfeld J, Griffin RG. High frequency dynamic nuclear polarization. Acc Chem Res 2013; 46:1933-41. [PMID: 23597038 PMCID: PMC3778063 DOI: 10.1021/ar300348n] [Citation(s) in RCA: 384] [Impact Index Per Article: 34.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
During the three decades 1980-2010, magic angle spinning (MAS) NMR developed into the method of choice to examine many chemical, physical, and biological problems. In particular, a variety of dipolar recoupling methods to measure distances and torsion angles can now constrain molecular structures to high resolution. However, applications are often limited by the low sensitivity of the experiments, due in large part to the necessity of observing spectra of low-γ nuclei such as the I = 1/2 species (13)C or (15)N. The difficulty is still greater when quadrupolar nuclei, such as (17)O or (27)Al, are involved. This problem has stimulated efforts to increase the sensitivity of MAS experiments. A particularly powerful approach is dynamic nuclear polarization (DNP) which takes advantage of the higher equilibrium polarization of electrons (which conventionally manifests in the great sensitivity advantage of EPR over NMR). In DNP, the sample is doped with a stable paramagnetic polarizing agent and irradiated with microwaves to transfer the high polarization in the electron spin reservoir to the nuclei of interest. The idea was first explored by Overhauser and Slichter in 1953. However, these experiments were carried out on static samples, at magnetic fields that are low by current standards. To be implemented in contemporary MAS NMR experiments, DNP requires microwave sources operating in the subterahertz regime, roughly 150-660 GHz, and cryogenic MAS probes. In addition, improvements were required in the polarizing agents, because the high concentrations of conventional radicals that are required to produce significant enhancements compromise spectral resolution. In the last two decades, scientific and technical advances have addressed these problems and brought DNP to the point where it is achieving wide applicability. These advances include the development of high frequency gyrotron microwave sources operating in the subterahertz frequency range. In addition, low temperature MAS probes were developed that permit in situ microwave irradiation of the samples. And, finally, biradical polarizing agents were developed that increased the efficiency of DNP experiments by factors of ∼4 at considerably lower paramagnet concentrations. Collectively, these developments have made it possible to apply DNP on a routine basis to a number of different scientific endeavors, most prominently in the biological and material sciences. This Account reviews these developments, including the primary mechanisms used to transfer polarization in high frequency DNP, and the current choice of microwave sources and biradical polarizing agents. In addition, we illustrate the utility of the technique with a description of applications to membrane and amyloid proteins that emphasizes the unique structural information that is available in these two cases.
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Affiliation(s)
- Qing Zhe Ni
- Francis Bitter Magnet Laboratory, ‡Department of Chemistry, and §Plasma Science and Fusion Center, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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47
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Gelis I, Vitzthum V, Dhimole N, Caporini MA, Schedlbauer A, Carnevale D, Connell SR, Fucini P, Bodenhausen G. Solid-state NMR enhanced by dynamic nuclear polarization as a novel tool for ribosome structural biology. JOURNAL OF BIOMOLECULAR NMR 2013; 56:85-93. [PMID: 23689811 DOI: 10.1007/s10858-013-9721-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 03/07/2013] [Indexed: 06/02/2023]
Abstract
The impact of Nuclear Magnetic Resonance (NMR) on studies of large macromolecular complexes hinges on improvements in sensitivity and resolution. Dynamic nuclear polarization (DNP) in the solid state can offer improved sensitivity, provided sample preparation is optimized to preserve spectral resolution. For a few nanomoles of intact ribosomes and an 800 kDa ribosomal complex we demonstrate that the combination of DNP and magic-angle spinning NMR (MAS-NMR) allows one to overcome current sensitivity limitations so that homo- and heteronuclear (13)C and (15)N NMR correlation spectra can be recorded. Ribosome particles, directly pelleted and frozen into an NMR rotor, yield DNP signal enhancements on the order of ~25-fold and spectra that exhibit narrow linewidths, suitable for obtaining site-specific information. We anticipate that the same approach is applicable to other high molecular weight complexes.
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Affiliation(s)
- Ioannis Gelis
- Buchmann Institute for Molecular Life Sciences, Institute of Organic Chemistry and Chemical Biology, Goethe University Frankfurt, Max-von-Laue-Str. 15, 60438 Frankfurt am Main, Germany
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48
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Andreas LB, Barnes AB, Corzilius B, Chou JJ, Miller EA, Caporini M, Rosay M, Griffin RG. Dynamic nuclear polarization study of inhibitor binding to the M2(18-60) proton transporter from influenza A. Biochemistry 2013; 52:2774-82. [PMID: 23480101 DOI: 10.1021/bi400150x] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We demonstrate the use of dynamic nuclear polarization (DNP) to elucidate ligand binding to a membrane protein using dipolar recoupling magic angle spinning (MAS) NMR. In particular, we detect drug binding in the proton transporter M2(18-60) from influenza A using recoupling experiments at room temperature and with cryogenic DNP. The results indicate that the pore binding site of rimantadine is correlated with previously reported widespread chemical shift changes, suggesting functional binding in the pore. Futhermore, the (15)N-labeled ammonium of rimantadine was observed near A30 (13)Cβ and G34 (13)Cα, suggesting a possible hydrogen bond to A30 carbonyl. Cryogenic DNP was required to observe the weaker external binding site(s) in a ZF-TEDOR spectrum. This approach is generally applicable, particularly for weakly bound ligands, in which case the application of MAS NMR dipolar recoupling requires the low temperatures to quench dynamic exchange processes. For the fully protonated samples investigated, we observed DNP signal enhancements of ~10 at 400 MHz using only 4-6 mM of the polarizing agent TOTAPOL. At 600 MHz and with DNP, we measured a distance between the drug and the protein to a precision of 0.2 Å.
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Affiliation(s)
- Loren B Andreas
- Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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49
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Ong TC, Mak-Jurkauskas ML, Walish JJ, Michaelis VK, Corzilius B, Smith AA, Clausen AM, Cheetham JC, Swager TM, Griffin RG. Solvent-free dynamic nuclear polarization of amorphous and crystalline ortho-terphenyl. J Phys Chem B 2013; 117:3040-6. [PMID: 23421391 DOI: 10.1021/jp311237d] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dynamic nuclear polarization (DNP) of amorphous and crystalline ortho-terphenyl (OTP) in the absence of glass forming agents is presented in order to gauge the feasibility of applying DNP to pharmaceutical solid-state nuclear magnetic resonance experiments and to study the effect of intermolecular structure, or lack thereof, on the DNP enhancement. By way of (1)H-(13)C cross-polarization, we obtained a DNP enhancement (ε) of 58 for 95% deuterated OTP in the amorphous state using the biradical bis-TEMPO terephthalate (bTtereph) and ε of 36 in the crystalline state. Measurements of the (1)H T1 and electron paramagnetic resonance experiments showed the crystallization process led to phase separation of the polarization agent, creating an inhomogeneous distribution of radicals within the sample. Consequently, the effective radical concentration was decreased in the bulk OTP phase, and long-range (1)H-(1)H spin diffusion was the main polarization propagation mechanism. Preliminary DNP experiments with the glass-forming anti-inflammation drug, indomethacin, showed promising results, and further studies are underway to prepare DNP samples using pharmaceutical techniques.
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Affiliation(s)
- Ta-Chung Ong
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Jawla S, Ni QZ, Barnes A, Guss W, Daviso E, Herzfeld J, Griffin R, Temkin R. Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy. JOURNAL OF INFRARED, MILLIMETER AND TERAHERTZ WAVES 2013; 34:42-52. [PMID: 23539422 PMCID: PMC3607393 DOI: 10.1007/s10762-012-9947-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a 13C-Urea sample using this gyrotron.
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Affiliation(s)
- Sudheer Jawla
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA-02139, USA
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