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Abstract
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Thanks to recent
improvements in NMR spectrometer hardware and
pulse sequence design, modern 13C NMR has become a useful
tool for biomolecular applications. The complete assignment of a protein
can be accomplished by using 13C detected multinuclear
experiments and it can provide unique information relevant for the
study of a variety of different biomolecules including paramagnetic
proteins and intrinsically disordered proteins. A wide range of NMR
observables can be measured, concurring to the structural and dynamic
characterization of a protein in isolation, as part of a larger complex,
or even inside a living cell. We present the different properties
of 13C with respect to 1H, which provide the
rationale for the experiments developed and their application, the
technical aspects that need to be faced, and the many experimental
variants designed to address different cases. Application areas where
these experiments successfully complement proton NMR are also described.
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Affiliation(s)
- Isabella C Felli
- Department of Chemistry "Ugo Schiff" and Magnetic Resonance Center, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino (Florence), Italy
| | - Roberta Pierattelli
- Department of Chemistry "Ugo Schiff" and Magnetic Resonance Center, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino (Florence), Italy
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2
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Comadoll CG, Henke WC, Hopkins Leseberg JA, Douglas JT, Oliver AG, Day VW, Blakemore JD. Examining the Modular Synthesis of [Cp*Rh] Monohydrides Supported by Chelating Diphosphine Ligands. Organometallics 2021. [DOI: 10.1021/acs.organomet.1c00525] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chelsea G. Comadoll
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Wade C. Henke
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Julie A. Hopkins Leseberg
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - Justin T. Douglas
- Nuclear Magnetic Resonance Laboratory, Molecular Structures Group, University of Kansas, 2034 Becker Drive, Lawrence, Kansas 66047, United States
| | - Allen G. Oliver
- Department of Chemistry and Biochemistry, University of Notre Dame, 149 Stepan Chemistry, Notre Dame, Indiana 46556, United States
| | - Victor W. Day
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
| | - James D. Blakemore
- Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States
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3
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Haller JD, Bodor A, Luy B. Real-time pure shift measurements for uniformly isotope-labeled molecules using X-selective BIRD homonuclear decoupling. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 302:64-71. [PMID: 30965191 DOI: 10.1016/j.jmr.2019.03.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 03/28/2019] [Accepted: 03/29/2019] [Indexed: 06/09/2023]
Abstract
We introduce a novel selective inversion element for chunked homonuclear decoupling that combines isotope selection via BIRD-filtering with band-selective inversion on the X-heteronucleus and allows efficient real-time decoupling of homonuclear and heteronuclear couplings. It is especially suitable for uniformly isotope-labeled compounds. We discuss in detail the inversion element based on band-selective refocusing on the X-nuclei (BASEREX), highlighting in particular the role of appropriate band-selective shaped refocusing pulses and the application of broadband X-pulses for an effective BIRDd element during homodecoupling. The approach is experimentally verified and studied in detail using uniformly 13C-labeled glucose and a uniformly 15N,13C-labeled amino acid mixture.
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Affiliation(s)
- Jens D Haller
- Institut für Organische Chemie and Institut für Biologische Grenzflächen 4 - Magnetische Resonanz, Karlsruher Institut für Technologie (KIT), Fritz-Haber-Weg 6, 76133 Karlsruhe, Germany
| | - Andrea Bodor
- Eötvös Loránd University, Institute of Chemistry, Laboratory of Structural Chemistry and Biology, Pázmány Péter sétány 1/a, Budapest 1117, Hungary
| | - Burkhard Luy
- Institut für Organische Chemie and Institut für Biologische Grenzflächen 4 - Magnetische Resonanz, Karlsruher Institut für Technologie (KIT), Fritz-Haber-Weg 6, 76133 Karlsruhe, Germany.
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4
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Görling B, Bermel W, Bräse S, Luy B. Homonuclear decoupling by projection reconstruction. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2018; 56:1006-1020. [PMID: 30058249 DOI: 10.1002/mrc.4784] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 06/16/2018] [Accepted: 07/10/2018] [Indexed: 06/08/2023]
Abstract
Similar to J-resolved spectroscopy, also, heteronuclear multiple bond correlation (HMBC), heteronuclear single bond correlation (HSBC), and heteronuclear multiple quantum coherence (HMQC) types of correlation experiments result in homonuclear tilted multiplet patterns. On the example of the high-resolution heteronuclear single bond correlation (HR-HSBC) pulse sequence, it is shown how the tilt angle can be varied within a wide range of positive and negative values. Projection along the tilt angles in all cases results in homonuclear decoupling. Using well-known projection reconstruction techniques, the different tilt angles can be used to reconstruct a homonuclear decoupled two-dimensional correlation spectrum. The concept is proven and further refined by segmental projection reconstruction and the use of a clean in-phase heteronuclear single quantum correlation (CLIP-HSQC) spectrum with an effective zero tilt angle for further filtering. The proof of principle, its application to one-bond coupling measurement, as well as a basic HMBC, and a detailed discussion with comparison to other homodecoupling techniques are given.
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Affiliation(s)
- Benjamin Görling
- Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
- Institute for Biological Interfaces 4 - Magnetic Resonance, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
- Bruker Biospin GmbH, Rheinstetten, Germany
| | | | - Stefan Bräse
- Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| | - Burkhard Luy
- Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
- Institute for Biological Interfaces 4 - Magnetic Resonance, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
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Castañar L, Parella T. Broadband 1H homodecoupled NMR experiments: recent developments, methods and applications. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2015; 53:399-426. [PMID: 25899911 DOI: 10.1002/mrc.4238] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 02/23/2015] [Accepted: 02/25/2015] [Indexed: 06/04/2023]
Abstract
In recent years, a great interest in the development of new broadband 1H homonuclear decoupled techniques providing simplified JHH multiplet patterns has emerged again in the field of small molecule NMR. The resulting highly resolved 1H NMR spectra display resonances as collapsed singlets, therefore minimizing signal overlap and expediting spectral analysis. This review aims at presenting the most recent advances in pure shift NMR spectroscopy, with a particular emphasis to the Zangger-Sterk experiment. A detailed discussion about the most relevant practical aspects in terms of pulse sequence design, selectivity, sensitivity, spectral resolution and performance is provided. Finally, the implementation of the different reported strategies into traditional 1D and 2D NMR experiments is described while several practical applications are also reviewed.
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Affiliation(s)
- Laura Castañar
- Servei de Ressonància Magnètica Nuclear and Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193, Bellaterra, Barcelona, Catalonia, Spain
| | - Teodor Parella
- Servei de Ressonància Magnètica Nuclear and Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193, Bellaterra, Barcelona, Catalonia, Spain
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Felli IC, Pierattelli R. Spin-state-selective methods in solution- and solid-state biomolecular 13C NMR. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2015; 84-85:1-13. [PMID: 25669738 DOI: 10.1016/j.pnmrs.2014.10.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 10/26/2014] [Indexed: 06/04/2023]
Abstract
Spin-state-selective methods to achieve homonuclear decoupling in the direct acquisition dimension of (13)C detected NMR experiments have been one of the key contributors to converting (13)C detected NMR experiments into really useful tools for studying biomolecules. We discuss here in detail the various methods that have been proposed, summarize the large array of new experiments that have been developed and present applications to different kinds of proteins in different aggregation states.
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Affiliation(s)
- Isabella C Felli
- Magnetic Resonance Center (CERM) and Department of Chemistry "Ugo Schiff", University of Florence, Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy.
| | - Roberta Pierattelli
- Magnetic Resonance Center (CERM) and Department of Chemistry "Ugo Schiff", University of Florence, Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy.
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Castañar L, Nolis P, Virgili A, Parella T. Full sensitivity and enhanced resolution in homodecoupled band-selective NMR experiments. Chemistry 2013; 19:17283-6. [PMID: 24218341 DOI: 10.1002/chem.201303235] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Laura Castañar
- Servei Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)
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Sakhaii P, Haase B, Bermel W. Experimental access to HSQC spectra decoupled in all frequency dimensions. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 199:192-198. [PMID: 19467611 DOI: 10.1016/j.jmr.2009.04.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 04/20/2009] [Accepted: 04/24/2009] [Indexed: 05/27/2023]
Abstract
A new operator called RESET "Reducing nuclEar Spin multiplicitiEs to singuleTs" is presented to acquire broadband proton decoupled proton spectra in one and two dimensions. Basically, the homonuclear decoupling is achieved through the application of bilinear rotation pulses and delays. A [BIRD](r,x) pulse building block is used to selectively invert all proton magnetization remotely attached to (13)C isotopes, which is equivalent to a scalar J decoupling of the protons directly attached to (13)C from all other protons in the spin system. In conjunction with an appropriate data processing technique pure shift proton spectra are obtained. For this purpose, the concept of constant time acquisition in the observe dimension is exploited. Both ideas were merged together producing superior HSQC based pseudo 3D pulse sequences. The resulting HSQC spectra show cross peaks with collapsed multiplet structures and singlet responses for the proton chemical shift frequencies. An unambiguous assignment of signals from overcrowded spectra becomes much easier. Finally, the recently introduced SHARC technique is exploited to enhance the capability of the scalar J decoupling method. A significant reduction of the total measurement time is achieved. The time is saved by reducing the number of (13)C chemical shift evolution increments and working with superimposed narrow spectral bandwidths in the (13)C indirect domain.
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Affiliation(s)
- Peyman Sakhaii
- Sanofi-Aventis Deutschland GmbH, Process Development Chemistry, PDC SPS (Structure Elucidation/Project & Production Support), Industriepark Hoechst, Frankfurt/Main, Germany.
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Van Melckebeke H, Simorre JP, Brutscher B. Suppression of artifacts induced by homonuclear decoupling in amino-acid-type edited methyl 1H-13C correlation experiments. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2004; 170:199-205. [PMID: 15388081 DOI: 10.1016/j.jmr.2004.06.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2004] [Revised: 06/24/2004] [Indexed: 05/24/2023]
Abstract
A detailed theoretical and experimental analysis of the artifacts induced by homonuclear band-selective decoupling during CT frequency labeling is presented. The effects are discussed in the context of an amino-acid-type editing filter implemented in (1)H-(13)C CT-HSQC experiments of methyl groups in proteins. It is shown that both Bloch-Siegert shifts and modulation sidebands are efficiently suppressed by using additional off-resonance decoupling as proposed by Zhang and Gorenstein [J. Magn. Reson. 132 (1998) 81], and appropriate adjustment of a set of pulse sequence parameters. The theoretical predictions are confirmed by experiments performed on (13)C-labeled protein samples, yielding artifact-free amino-acid-type edited methyl spectra.
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Affiliation(s)
- Hélène Van Melckebeke
- Institut de Biologie Structurale, Jean-Pierre Ebel C.N.R.S.-C.E.A.-UJF 41, rue Jules Horowitz, 38027 Grenoble Cedex, France
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Kövér KE, Batta G. More line narrowing in TROSY by decoupling of long-range couplings: shift correlation and 1JNC' coupling constant measurements. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2004; 170:184-190. [PMID: 15388079 DOI: 10.1016/j.jmr.2004.06.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Revised: 04/27/2004] [Indexed: 05/24/2023]
Abstract
Since the introduction of RDCs in high-resolution NMR studies of macromolecules, there is a growing interest in the development of accurate, and sensitive methods for determining coupling constants. Most methods for extracting these couplings are based on the measurement of the splitting between multiplet components in J-coupled spectra. However, these methods are often unreliable since undesired multiple-bond couplings can considerably broaden the multiplet components and consequently make accurate determination of their position difficult. To demonstrate one approach to this problem, G-BIRD((r)) decoupled TROSY sequences are proposed for the measurement of (1)J(NH) and (1)J(NC') coupling constants. Resolved or unresolved splittings due to remote protons are removed by a G-BIRD((r)) module employed during t(1) and as a result, spectra with narrow, well-resolved peaks are obtained from which heteronuclear one-bond couplings can be accurately measured. Moreover, introduction of a spin-state-selective alpha/beta-filter in the TROSY sequence allows the separation of the (1)J(NC') doublet components into two subspectra which contain the same number of peaks as the regular TROSY spectrum. The (1)J(NC') couplings are obtained from the displacement between the corresponding peaks in the subspectra.
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Affiliation(s)
- Katalin E Kövér
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary.
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Van Melckebeke H, Simorre JP, Brutscher B. Amino Acid-Type Edited NMR Experiments for Methyl−Methyl Distance Measurement in 13C-Labeled Proteins. J Am Chem Soc 2004; 126:9584-91. [PMID: 15291562 DOI: 10.1021/ja0489644] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
New NMR experiments are presented for the measurement of methyl-methyl distances in (13)C-labeled proteins from a series of amino acid-type separated 2D or 3D NOESY spectra. Hadamard amino acid-type encoding of the proximal methyl groups provides the high spectral resolution required for unambiguous methyl-methyl NOE assignment, which is particularly important for fast global fold determination of proteins. The experiments can be applied to a wide range of protein systems, as exemplified for two small proteins, ubiquitin and MerAa, and the 30 kDa BRP-Blm complex.
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Affiliation(s)
- Hélène Van Melckebeke
- Institut de Biologie Structurale, Jean-Pierre Ebel CNRS-CEA-UJF, 41, rue Jules Horowitz, 38027 Grenoble Cedex, France
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Bermel W, Bertini I, Felli IC, Kümmerle R, Pierattelli R. 13C direct detection experiments on the paramagnetic oxidized monomeric copper, zinc superoxide dismutase. J Am Chem Soc 2004; 125:16423-9. [PMID: 14692785 DOI: 10.1021/ja037676p] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this report, the use of 13C direct detection has been pursued in 2D experiments (13C-13C COSY, 13C-13C COCAMQ, 13C-13C NOESY) to detect broad lines in nuclear magnetic resonance spectra of paramagnetic metalloproteins. The sample is a monomeric oxidized copper, zinc superoxide dismutase. Thanks to direct detection probeheads, cryogenic technology, and implementation of 13C band-selective homodecoupling, many broadened signals were detected. Proton signals for the same residues escaped detection in 1H and 1H-15N HSQC experiments because of the broadening. Only the 13C signals which experience large contact coupling escaped detection, i.e., the 13C nuclei of the metal coordinated histidines. Otherwise, nuclei as close to copper(II) as 4 A can be detected. Paramagnetic-based restraints can in principle be used for solution structure determination of paramagnetic metalloproteins and in copper(II) proteins in particular. The present study is significant also for the study of large diamagnetic proteins for which proton relaxation makes proton-based spectroscopy not adequate.
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Affiliation(s)
- E Kupce
- Varian, Incorporated, Walton-on-Thames, Surrey KT12 2QF, United Kingdom
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Kövér KE, Batta G. J-modulated TROSY experiment extends the limits of homonuclear coupling measurements for larger proteins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2001; 151:60-64. [PMID: 11444937 DOI: 10.1006/jmre.2001.2344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This paper describes the use of a TROSY experimental scheme and its variant extended with a scaled J-modulation spin-echo sequence for accurate and sensitive measurement of homonuclear 3J(H(N)H(alpha)) coupling constants in larger proteins with uniform 15N labeling. Exclusive selection of the most slowly relaxing component of a 15N-1H multiplet by the TROSY approach leads to substantial improvement in resolution; this is a prerequisite for accurate measurement of couplings from the 1H multiplets directly along the 1H frequency dimension or from the J-scaled doublets along the 15N frequency dimension.
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Affiliation(s)
- K E Kövér
- Department of Inorganic and Analytical Chemistry, University of Debrecen, Hungary.
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Hennig M, Bermel W, Schwalbe H, Griesinger C. Determination of ψ Torsion Angle Restraints from 3J(Cα,Cα) and 3J(Cα,HN) Coupling Constants in Proteins. J Am Chem Soc 2000. [DOI: 10.1021/ja9928834] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mirko Hennig
- Contribution from the Institut für Organische Chemie, Universität Frankfurt, Marie-Curie Strasse 11, D-60439 Frankfurt/Main, Germany, Bruker Analytik GmbH, Silberstreifen, D-76287 Rheinstetten, Germany, Massachusetts Institute of Technology, Department of Chemistry, Francis Bitter Magnet Laboratory, 170 Albany Street, Building NW14, Cambridge, Massachusetts 02139, and Max Planck Institut für Biophysikalische Chemie, Am Faβberg, D-37077 Göttingen, Germany
| | - Wolfgang Bermel
- Contribution from the Institut für Organische Chemie, Universität Frankfurt, Marie-Curie Strasse 11, D-60439 Frankfurt/Main, Germany, Bruker Analytik GmbH, Silberstreifen, D-76287 Rheinstetten, Germany, Massachusetts Institute of Technology, Department of Chemistry, Francis Bitter Magnet Laboratory, 170 Albany Street, Building NW14, Cambridge, Massachusetts 02139, and Max Planck Institut für Biophysikalische Chemie, Am Faβberg, D-37077 Göttingen, Germany
| | - Harald Schwalbe
- Contribution from the Institut für Organische Chemie, Universität Frankfurt, Marie-Curie Strasse 11, D-60439 Frankfurt/Main, Germany, Bruker Analytik GmbH, Silberstreifen, D-76287 Rheinstetten, Germany, Massachusetts Institute of Technology, Department of Chemistry, Francis Bitter Magnet Laboratory, 170 Albany Street, Building NW14, Cambridge, Massachusetts 02139, and Max Planck Institut für Biophysikalische Chemie, Am Faβberg, D-37077 Göttingen, Germany
| | - Christian Griesinger
- Contribution from the Institut für Organische Chemie, Universität Frankfurt, Marie-Curie Strasse 11, D-60439 Frankfurt/Main, Germany, Bruker Analytik GmbH, Silberstreifen, D-76287 Rheinstetten, Germany, Massachusetts Institute of Technology, Department of Chemistry, Francis Bitter Magnet Laboratory, 170 Albany Street, Building NW14, Cambridge, Massachusetts 02139, and Max Planck Institut für Biophysikalische Chemie, Am Faβberg, D-37077 Göttingen, Germany
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Zhang S, Gorenstein DG. "BEST" homonuclear adiabatic decoupling for 13C- and 15N-double-labeled proteins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 1999; 138:281-287. [PMID: 10341132 DOI: 10.1006/jmre.1999.1753] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The cyclic irradiation sidebands appearing in homonuclear adiabatic decoupling are calculated in detail, which reveals the origin of the antisymmetric sidebands. The sidebands can be inverted by inserting an initial decoupling with a different period, but the same f1rms as the main decoupling that is required for Bloch-Siegert shift compensation. The sidebands can be eliminated in a broad decoupling range by adding spectra of opposite sidebands. Based on this scheme, an offset-independent double-adiabatic decoupling, named Bloch-Siegert Shift Eliminated and Cyclic Sideband Trimmed Double-Adiabatic Decoupling, or "BEST" decoupling for short, is constructed, which not only compensates the Bloch-Siegert shift as shown earlier by Zhang and Gorenstein (1998) but also eliminates residual sidebands effectively.
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Affiliation(s)
- S Zhang
- Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, Texas 77555-1157, USA
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Miles CS, Weigelt J, Stamford NP, Dammerova N, Otting G, Dixon NE. Precise limits of the N-terminal domain of DnaB helicase determined by NMR spectroscopy. Biochem Biophys Res Commun 1997; 231:126-30. [PMID: 9070233 DOI: 10.1006/bbrc.1997.6059] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Two separate N-terminal fragments of the 470-amino-acid Escherichia coli DnaB helicase, comprising residues 1-142 and 1-161, were expressed in E. coli. The proteins were extracted in a soluble fraction, purified, and characterised physically. In contrast to the full-length protein, which is hexameric, both fragments exist as monomers in solution, as demonstrated by sedimentation equilibrium measurements. CD spectroscopy was used to confirm that the 161-residue fragment is highly structured (mostly alpha-helical) and undergoes reversible thermal denaturation. The structurally well-defined core of the N-terminal domain of the DnaB helicase is composed of residues 24 to 136, as determined by assignment of resonances from flexible residues in NMR spectra. The 1H NMR signals of the flexible residues are located at random coil chemical shifts, and their linewidths are significantly narrower than those of the structured core, indicating complete disorder and increased mobility on the nanosecond time scale. The results support the idea of a flexible hinge region between the N- and C-terminal domains of the native hexameric DnaB protein.
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Affiliation(s)
- C S Miles
- Centre for Molecular Structure and Function, Research School of Chemistry, Australian National University, Canberra, Australia
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