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Ning P, Lane D, Ghosh Biswas R, Soong R, Schmidig D, Frei T, De Castro P, Kovacevic I, Graf S, Wegner S, Busse F, Kuehn T, Struppe J, Fey M, Stronks HJ, Monette M, Simpson MJ, Simpson AJ. Comprehensive Multiphase NMR Probehead with Reduced Radiofrequency Heating Improves the Analysis of Living Organisms and Heat-Sensitive Samples. Anal Chem 2021; 93:10326-10333. [PMID: 34259008 DOI: 10.1021/acs.analchem.1c01932] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Comprehensive multiphase (CMP) NMR, first described in 2012, combines all of the hardware components necessary to analyze all phases (solid, gel, and solution) in samples in their natural state. In combination with spectral editing experiments, it can fully differentiate phases and study the transfer of chemical species across and between phases, providing unprecedented molecular-level information in unaltered natural systems. However, many natural samples, such as swollen soils, plants, and small organisms, contain water, salts, and ionic compounds, making them electrically lossy and susceptible to RF heating, especially when using high-strength RF fields required to select the solid domains. While dedicated reduced-heating probes have been developed for solid-state NMR, to date, all CMP-NMR probes have been based on solenoid designs, which can lead to problematic sample heating. Here, a new prototype CMP probe was developed, incorporating a loop gap resonator (LGR) for decoupling. Temperature increases are monitored in salt solutions analogous to those in small aquatic organisms and then tested in vivo on Hyalella azteca (freshwater shrimp). In the standard CMP probe (solenoid), 80% of organisms died within 4 h under high-power decoupling, while in the LGR design, all organisms survived the entire test period of 12 h. The LGR design reduced heating by a factor of ∼3, which allowed 100 kHz decoupling to be applied to salty samples with generally ≤10 °C sample heating. In addition to expanding the potential for in vivo research, the ability to apply uncompromised high-power decoupling could be beneficial for multiphase samples containing true crystalline solids that require the strongest possible decoupling fields for optimal detection.
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Affiliation(s)
- Paris Ning
- Environmental NMR Centre, University of Toronto, Toronto, Ontario M1C 1A4, Canada
| | - Daniel Lane
- Environmental NMR Centre, University of Toronto, Toronto, Ontario M1C 1A4, Canada
| | | | - Ronald Soong
- Environmental NMR Centre, University of Toronto, Toronto, Ontario M1C 1A4, Canada
| | - Daniel Schmidig
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Thomas Frei
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Peter De Castro
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Ivan Kovacevic
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Stephan Graf
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Sebastian Wegner
- Bruker BioSpin GmbH, Silberstreifen 4, 76287 Rheinstetten, Germany
| | - Falko Busse
- Bruker BioSpin GmbH, Silberstreifen 4, 76287 Rheinstetten, Germany
| | - Till Kuehn
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Jochem Struppe
- Bruker BioSpin Corp., 15 Fortune Drive, Billerica, Massachusetts 01821-3991, United States
| | - Michael Fey
- Bruker BioSpin Corp., 15 Fortune Drive, Billerica, Massachusetts 01821-3991, United States
| | - Henry J Stronks
- Bruker Ltd., 2800 High Point Drive, Milton, Ontario L9T 6P4, Canada
| | - Martine Monette
- Bruker Ltd., 2800 High Point Drive, Milton, Ontario L9T 6P4, Canada
| | - Myrna J Simpson
- Environmental NMR Centre, University of Toronto, Toronto, Ontario M1C 1A4, Canada
| | - André J Simpson
- Environmental NMR Centre, University of Toronto, Toronto, Ontario M1C 1A4, Canada
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2
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Bernard GM, Michaelis VK. Lead-207 NMR spectroscopy at 1.4 T: Application of benchtop instrumentation to a challenging I = ½ nucleus. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2020; 58:1203-1212. [PMID: 32364623 DOI: 10.1002/mrc.5036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 04/23/2020] [Accepted: 04/27/2020] [Indexed: 06/11/2023]
Abstract
The practicality of obtaining liquid- and solid-state 207 Pb nuclear magnetic resonance (NMR) spectra with a low permanent-field magnet is investigated. Obtaining 207 Pb NMR spectra of salts in solution is shown to be viable for samples as dilute as 0.05 M. The concentration dependence of the 207 Pb chemical shifts for lead nitrate was investigated; the results are comparable with those obtained with high-field instruments. Likewise, the isotope effect of substituting D2 O for H2 O as the solvent was investigated and found to be comparable with those reported previously. Obtaining solid-state 207 Pb NMR spectra is challenging, but we demonstrate the ability to obtain such spectra for three unique solid samples. An axially symmetric 207 Pb powder pattern for lead nitrate and the powder pattern expected for lead chloride reveal linewidths dominated by shielding anisotropy, while 207 Pb-35/37 Cl J-coupling dominates in the methylammonium lead chloride perovskite material. Finally, recent innovations and the future potential of the instruments are considered.
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Affiliation(s)
- Guy M Bernard
- Gunning-Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, Canada
| | - Vladimir K Michaelis
- Gunning-Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, Canada
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3
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Zhang D, Itin B, McDermott AE. TmDOTP: An NMR-based thermometer for magic angle spinning NMR experiments. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 308:106574. [PMID: 31541931 PMCID: PMC7296554 DOI: 10.1016/j.jmr.2019.106574] [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: 03/12/2019] [Revised: 08/13/2019] [Accepted: 08/15/2019] [Indexed: 05/06/2023]
Abstract
Solid state NMR is a powerful tool to probe membrane protein structure and dynamics in native lipid membranes. Sample heating during solid state NMR experiments can be caused by magic angle spinning and radio frequency irradiation such heating produces uncertainties in the sample temperature and temperature distribution, which can in turn lead to line broadening and sample deterioration. To measure sample temperatures in real time and to quantify thermal gradients and their dependence on radio frequency irradiation or spinning frequency, we use the chemical shift thermometer TmDOTP, a lanthanide complex. The H6 TmDOTP proton NMR peak has a large chemical shift (-176.3 ppm at 275 K) and it is well resolved from the protein and lipid proton spectrum. Compared to other NMR thermometers (e.g., the proton NMR signal of water), the proton spectrum of TmDOTP, particularly the H6 proton line, exhibits very high thermal sensitivity and resolution. In MAS studies of proteoliposomes we identify two populations of TmDOTP with differing temperatures and dependency on the radio frequency irradiation power. We interpret these populations as arising from the supernatant and the pellet, which is sedimented during sample spinning. In this study, we demonstrate that TmDOTP is an excellent internal standard for monitoring real-time temperatures of biopolymers without changing their properties or obscuring their spectra. Real time temperature calibration is expected to be important for the interpretation of dynamics and other properties of biopolymers.
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Affiliation(s)
- Dongyu Zhang
- Department of Chemistry, Columbia University, New York, NY 10027, United States
| | - Boris Itin
- New York Structural Biology Center, New York, NY 10027, United States
| | - Ann E McDermott
- Department of Chemistry, Columbia University, New York, NY 10027, United States.
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4
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Kocman V, Di Mauro GM, Veglia G, Ramamoorthy A. Use of paramagnetic systems to speed-up NMR data acquisition and for structural and dynamic studies. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 102:36-46. [PMID: 31325686 PMCID: PMC6698407 DOI: 10.1016/j.ssnmr.2019.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/10/2019] [Accepted: 07/11/2019] [Indexed: 05/05/2023]
Abstract
NMR spectroscopy is a powerful experimental technique to study biological systems at the atomic resolution. However, its intrinsic low sensitivity results in long acquisition times that in extreme cases lasts for days (or even weeks) often exceeding the lifetime of the sample under investigation. Different paramagnetic agents have been used in an effort to decrease the spin-lattice (T1) relaxation times of the studied nuclei, which are the main cause for long acquisition times necessary for signal averaging to enhance the signal-to-noise ratio of NMR spectra. Consequently, most of the experimental time is "wasted" in waiting for the magnetization to recover between successive scans. In this review, we discuss how to set up an optimal paramagnetic relaxation enhancement (PRE) system to effectively reduce the T1 relaxation times avoiding significant broadening of NMR signals. Additionally, we describe how PRE-agents can be used to provide structural and dynamic information and can even be used to follow the intermediates of chemical reactions and to speed-up data acquisition. We also describe the unique challenges and benefits associated with the application of PRE to solid-state NMR spectroscopy, explaining how the use of PREs is more complex for membrane mimetic systems as PREs can also be exploited to change the alignment of oriented membrane systems. Functionalization of membrane mimetics, such as bicelles, can provide a controlled region of paramagnetic effect that has the potential, together with the desired alignment, to provide crucial biologically relevant structural information. And finally, we discuss how paramagnetic metals can be utilized to further increase the dynamic nuclear polarization (DNP) effects and how to preserve the enhancements when dissolution DNP is implemented.
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Affiliation(s)
- Vojč Kocman
- Department of Chemistry, University of Michigan, Ann Arbor, MI, USA; Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA
| | | | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, Ann Arbor, MI, USA; Biophysics, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA.
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5
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Wang J, Zhang Z, Zhao W, Wang L, Yang J. Heating and temperature gradients of lipid bilayer samples induced by RF irradiation in MAS solid-state NMR experiments. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2016; 54:753-759. [PMID: 27161041 DOI: 10.1002/mrc.4450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 03/16/2016] [Accepted: 04/18/2016] [Indexed: 05/15/2023]
Abstract
The MAS solid-state NMR has been a powerful technique for studying membrane proteins within the native-like lipid bilayer environment. In general, RF irradiation in MAS NMR experiments can heat and potentially destroy expensive membrane protein samples. However, under practical MAS NMR experimental conditions, detailed characterization of RF heating effect of lipid bilayer samples is still lacking. Herein, using 1 H chemical shift of water for temperature calibration, we systematically study the dependence of RF heating on hydration levels and salt concentrations of three lipids in MAS NMR experiments. Under practical 1 H decoupling conditions used in biological MAS NMR experiments, three lipids show different dependence of RF heating on hydration levels as well as salt concentrations, which are closely associated with the properties of lipids. The maximum temperature elevation of about 10 °C is similar for the three lipids containing 200% hydration, which is much lower than that in static solid-state NMR experiments. The RF heating due to salt is observed to be less than that due to hydration, with a maximum temperature elevation of less than 4 °C in the hydrated samples containing 120 mmol l-1 of salt. Upon RF irradiation, the temperature gradient across the sample is observed to be greatly increased up to 20 °C, as demonstrated by the remarkable broadening of 1 H signal of water. Based on detailed characterization of RF heating effect, we demonstrate that RF heating and temperature gradient can be significantly reduced by decreasing the hydration levels of lipid bilayer samples from 200% to 30%. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Jing Wang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhengfeng Zhang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Weijing Zhao
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Liying Wang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Jun Yang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Center for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, China
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6
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Control and role of pH in peptide–lipid interactions in oriented membrane samples. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:833-41. [DOI: 10.1016/j.bbamem.2014.12.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 12/01/2014] [Accepted: 12/04/2014] [Indexed: 12/22/2022]
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7
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Mithu VS, Bakthavatsalam S, Madhu PK. (13)C-(13)c homonuclear recoupling in solid-state nuclear magnetic resonance at a moderately high magic-angle-spinning frequency. PLoS One 2013; 8:e50504. [PMID: 23326308 PMCID: PMC3542364 DOI: 10.1371/journal.pone.0050504] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 10/22/2012] [Indexed: 11/18/2022] Open
Abstract
Two-dimensional (13)C-(13)C correlation experiments are widely employed in structure determination of protein assemblies using solid-state nuclear magnetic resonance. Here, we investigate the process of (13)C-(13)C magnetisation transfer at a moderate magic-angle-spinning frequency of 30 kHz using some of the prominent second-order dipolar recoupling schemes. The effect of isotropic chemical-shift difference and spatial distance between two carbons and amplitude of radio frequency on (1)H channel on the magnetisation transfer efficiency of these schemes is discussed in detail.
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Affiliation(s)
- Venus Singh Mithu
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, India
| | - Subha Bakthavatsalam
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, India
| | - Perunthiruthy K. Madhu
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, India
- * E-mail:
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8
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Quinn CM, McDermott AE. Quantifying conformational dynamics using solid-state R₁ρ experiments. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 222:1-7. [PMID: 22820004 PMCID: PMC3572234 DOI: 10.1016/j.jmr.2012.05.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 05/14/2012] [Accepted: 05/20/2012] [Indexed: 05/14/2023]
Abstract
We demonstrate the determination of quantitative rates of molecular reorientation in the solid state with rotating frame (R(1ρ)) relaxation measurements. Reorientation of the carbon chemical shift anisotropy (CSA) tensor was used to probe site-specific conformational exchange in a model system, d(6)-dimethyl sulfone (d(6)-DMS). The CSA as a probe of exchange has the advantage that it can still be utilized when there is no dipolar mechanism (i.e. no protons attached to the site of interest). Other works have presented R(1ρ) measurements as a general indicator of dynamics, but this study extracts quantitative rates of molecular reorientation from the R(1ρ) values. Some challenges of this technique include precise knowledge of sample temperature and determining the R(2)(0) contribution to the observed relaxation rate from interactions other than molecular reorientation, such as residual dipolar couplings or fast timescale dynamics; determination of this term is necessary in order to quantify the exchange rate due to covariance between the 2 terms. Low-temperature experiments measured an R(2)(0) value of 1.8±0.2s(-1) Allowing for an additional relaxation term (R(2)(0)), which was modeled as both temperature-dependent and temperature-independent, rates of molecular reorientation were extracted from field strength-dependent R(1ρ) measurements at four different temperatures and the activation energy was determined from these exchange rates. The activation energies determined were 74.7±4.3kJ/mol and 71.7±2.9kJ/mol for the temperature-independent and temperature-dependent R(2)(0) models respectively, in excellent agreement with literature values. The results of this study suggest important methodological considerations for the application of the method to more complicated systems such as proteins, such as the importance of deuterating samples and the need to make assumptions regarding the R(2)(0) contribution to relaxation.
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9
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Demers JP, Chevelkov V, Lange A. Progress in correlation spectroscopy at ultra-fast magic-angle spinning: basic building blocks and complex experiments for the study of protein structure and dynamics. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2011; 40:101-113. [PMID: 21880471 DOI: 10.1016/j.ssnmr.2011.07.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 07/21/2011] [Accepted: 07/22/2011] [Indexed: 05/31/2023]
Abstract
Recent progress in multi-dimensional solid-state NMR correlation spectroscopy at high static magnetic fields and ultra-fast magic-angle spinning is discussed. A focus of the review is on applications to protein resonance assignment and structure determination as well as on the characterization of protein dynamics in the solid state. First, the consequences of ultra-fast spinning on sensitivity and sample heating are considered. Recoupling and decoupling techniques at ultra-fast MAS are then presented, as well as more complex experiments assembled from these basic building blocks. Furthermore, we discuss new avenues in biomolecular solid-state NMR spectroscopy that become feasible in the ultra-fast spinning regime, such as sensitivity enhancement based on paramagnetic doping, and the prospect of direct proton detection.
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Affiliation(s)
- Jean-Philippe Demers
- Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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10
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Debelouchina GT, Platt GW, Bayro MJ, Radford SE, Griffin RG. Magic angle spinning NMR analysis of beta2-microglobulin amyloid fibrils in two distinct morphologies. J Am Chem Soc 2010; 132:10414-23. [PMID: 20662519 PMCID: PMC2919207 DOI: 10.1021/ja102775u] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Beta(2)-microglobulin (beta(2)m) is the major structural component of amyloid fibrils deposited in a condition known as dialysis-related amyloidosis. Despite numerous studies that have elucidated important aspects of the fibril formation process in vitro, and a magic angle spinning (MAS) NMR study of the fibrils formed by a small peptide fragment, structural details of beta(2)m fibrils formed by the full-length 99-residue protein are largely unknown. Here, we present a site-specific MAS NMR analysis of fibrils formed by the full-length beta(2)m protein and compare spectra of fibrils prepared under two different conditions. Specifically, long straight (LS) fibrils are formed at pH 2.5, while a very different morphology denoted as worm-like (WL) fibrils is observed in preparations at pH 3.6. High-resolution MAS NMR spectra have allowed us to obtain (13)C and (15)N resonance assignments for 64 residues of beta(2)m in LS fibrils, including part of the highly mobile N-terminus. Approximately 25 residues did not yield observable signals. Chemical shift analysis of the sequentially assigned residues indicates that these fibrils contain an extensive beta-sheet core organized in a non-native manner, with a trans-P32 conformation. In contrast, WL fibrils exhibit more extensive dynamics and appear to have a smaller beta-sheet core than LS fibrils, although both cores seem to share some common elements. Our results suggest that the distinct macroscopic morphological features observed for the two types of fibrils result from variations in structure and dynamics at the molecular level.
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Affiliation(s)
- Galia T. Debelouchina
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Geoffrey W. Platt
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Marvin J. Bayro
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Sheena E. Radford
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
- Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Robert G. Griffin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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11
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Demers JP, Vijayan V, Becker S, Lange A. Tailored low-power cross-polarization under fast magic-angle spinning. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 205:216-23. [PMID: 20570194 DOI: 10.1016/j.jmr.2010.04.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 04/29/2010] [Indexed: 05/10/2023]
Abstract
High static magnetic fields and very fast magic-angle spinning (MAS) promise to improve resolution and sensitivity of solid-state NMR experiments. The fast MAS regime has permitted the development of low-power cross-polarization schemes, such as second-order cross-polarization (SOCP), which prevent heat deposition in the sample. Those schemes are however limited in bandwidth, as weak radio-frequency (RF) fields only cover a small chemical shift range for rare nuclei (e.g. (13)C). Another consideration is that the efficiency of cross-polarization is very sensitive to magnetization decay that occurs during the spin-lock pulse on the abundant nuclei (e.g. (1)H). Having characterized this decay in glutamine at 60 kHz MAS, we propose two complementary strategies to tailor cross-polarization to desired spectral regions at low RF power. In the case of multiple sites with small chemical shift dispersion, a larger bandwidth for SOCP is obtained by slightly increasing the RF power while avoiding recoupling conditions that lead to fast spin-lock decay. In the case of two spectral regions with large chemical shift offset, an extension of the existing low-power schemes, called MOD-CP, is introduced. It consists of a spin-lock on (1)H and an amplitude-modulated spin-lock on the rare nucleus. The range of excited chemical shifts is assessed by experimental excitation profiles and numerical simulation of an I(2)S spin system. All SOCP-based schemes exhibit higher sensitivity than high-power CP schemes, as demonstrated on solid (glutamine) and semi-solid (hydrated, micro-crystalline ubiquitin) samples.
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Affiliation(s)
- Jean-Philippe Demers
- Max Planck Institute for Biophysical Chemistry, Solid-state NMR, Göttingen 37077, Germany
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12
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Grant CV, Yang Y, Glibowicka M, Wu CH, Park SH, Deber CM, Opella SJ. A Modified Alderman-Grant Coil makes possible an efficient cross-coil probe for high field solid-state NMR of lossy biological samples. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 201:87-92. [PMID: 19733108 PMCID: PMC2800166 DOI: 10.1016/j.jmr.2009.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2009] [Revised: 08/10/2009] [Accepted: 08/10/2009] [Indexed: 05/11/2023]
Abstract
The design, construction, and performance of a cross-coil double-resonance probe for solid-state NMR experiments on lossy biological samples at high magnetic fields are described. The outer coil is a Modified Alderman-Grant Coil (MAGC) tuned to the (1)H frequency. The inner coil consists of a multi-turn solenoid coil that produces a B(1) field orthogonal to that of the outer coil. This results in a compact nested cross-coil pair with the inner solenoid coil tuned to the low frequency detection channel. This design has several advantages over multiple-tuned solenoid coil probes, since RF heating from the (1)H channel is substantially reduced, it can be tuned for samples with a wide range of dielectric constants, and the simplified circuit design and high inductance inner coil provides excellent sensitivity. The utility of this probe is demonstrated on two electrically lossy samples of membrane proteins in phospholipid bilayers (bicelles) that are particularly difficult for conventional NMR probes. The 72-residue polypeptide embedding the transmembrane helices 3 and 4 of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) (residues 194-241) requires a high salt concentration in order to be successfully reconstituted in phospholipid bicelles. A second application is to paramagnetic relaxation enhancement applied to the membrane-bound form of Pf1 coat protein in phospholipid bicelles where the resistance to sample heating enables high duty cycle solid-state NMR experiments to be performed.
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Affiliation(s)
- Christopher V. Grant
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
| | - Yuan Yang
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
| | - Mira Glibowicka
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto M5G 1X8, Ontario, Canada
| | - Chin H. Wu
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
| | - Sang Ho Park
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
| | - Charles M. Deber
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto M5G 1X8, Ontario, Canada
| | - Stanley J. Opella
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0307
- Corresponding Author. , 858.822.4820
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13
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McNeill SA, Gor’kov PL, Shetty K, Brey WW, Long JR. A low-E magic angle spinning probe for biological solid state NMR at 750 MHz. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 197:135-44. [PMID: 19138870 PMCID: PMC2659328 DOI: 10.1016/j.jmr.2008.12.008] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2008] [Revised: 12/02/2008] [Accepted: 12/05/2008] [Indexed: 05/02/2023]
Abstract
Crossed-coil NMR probes are a useful tool for reducing sample heating for biological solid state NMR. In a crossed-coil probe, the higher frequency (1)H field, which is the primary source of sample heating in conventional probes, is produced by a separate low-inductance resonator. Because a smaller driving voltage is required, the electric field across the sample and the resultant heating is reduced. In this work we describe the development of a magic angle spinning (MAS) solid state NMR probe utilizing a dual resonator. This dual resonator approach, referred to as "low-E," was originally developed to reduce heating in samples of mechanically aligned membranes. The study of inherently dilute systems, such as proteins in lipid bilayers, via MAS techniques requires large sample volumes at high field to obtain spectra with adequate signal-to-noise ratio under physiologically relevant conditions. With the low-E approach, we are able to obtain homogeneous and sufficiently strong radiofrequency fields for both (1)H and (13)C frequencies in a 4mm probe with a (1)H frequency of 750 MHz. The performance of the probe using windowless dipolar recoupling sequences is demonstrated on model compounds as well as membrane-embedded peptides.
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Affiliation(s)
- Seth A. McNeill
- Department of Electrical and Computer Engineering, University of Florida, 32611
| | | | - Kiran Shetty
- National High Magnetic Field Laboratory, Tallahassee, FL 32310
| | - William W. Brey
- National High Magnetic Field Laboratory, Tallahassee, FL 32310
| | - Joanna R. Long
- Department of Biochemistry and Molecular Biology and McKnight Brain Institute, University of Florida, Gainesville, Florida 32610
- Correspondence: telephone :(352)846-1506 fax :(352)392-3422
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Fernando Cobo M, Maliňáková K, Reichert D, Saalwächter K, Ribeiro deAzevedo E. Intermediate motions and dipolar couplings as studied by Lee–Goldburg cross-polarization NMR: Hartmann–Hahn matching profiles. Phys Chem Chem Phys 2009; 11:7036-47. [DOI: 10.1039/b907674c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Affiliation(s)
- Cecil Dybowski*
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - Shi Bai
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
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16
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Gor'kov PL, Witter R, Chekmenev EY, Nozirov F, Fu R, Brey WW. Low-E probe for (19)F-(1)H NMR of dilute biological solids. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 189:182-189. [PMID: 17920316 DOI: 10.1016/j.jmr.2007.09.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 09/05/2007] [Accepted: 09/13/2007] [Indexed: 05/25/2023]
Abstract
Sample heating induced by radio frequency (RF) irradiation presents a significant challenge to solid state NMR experiments in proteins and other biological systems, causing the sample to dehydrate which may result in distorted spectra and a damaged sample. In this work we describe a large volume, low-E (19)F-(1)H solid state NMR probe, which we developed for the 2D (19)F CPMG studies of dilute membrane proteins in a static and electrically lossy environment at 600MHz field. In (19)FCPMG and related multi-pulse (19)F-(1)H experiments the sample is heated by the conservative electric fields E produced in the sample coil at both (19)F and (1)H frequencies. Instead of using a traditional sample solenoid, our low-E (19)F-(1)H probe utilizes two orthogonal loop-gap resonators in order to minimize the conservative electric fields responsible for sample heating. Absence of the wavelength effects in loop-gap resonators results in homogeneous RF fields and enables the study of large sample volumes, an important feature for the dilute protein preparations. The orthogonal resonators also provide intrinsic isolation between the (19)F and (1)H channels, which is another major challenge for the (19)F-(1)H circuits where Larmor frequencies are only 6% apart. We detail steps to reduce (19)F background signals from the probe, which included careful choice of capacitor lubricants and manufacture of custom non-fluorinated coaxial cables. Application of the probe for two-dimensional (19)F CPMG spectroscopy in oriented lipid membranes is demonstrated with Flufenamic acid (FFA), a non-steroidal anti-inflammatory drug.
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Affiliation(s)
- Peter L Gor'kov
- National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.
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17
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Gor'kov PL, Chekmenev EY, Li C, Cotten M, Buffy JJ, Traaseth NJ, Veglia G, Brey WW. Using low-E resonators to reduce RF heating in biological samples for static solid-state NMR up to 900 MHz. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 185:77-93. [PMID: 17174130 DOI: 10.1016/j.jmr.2006.11.008] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Revised: 11/01/2006] [Accepted: 11/13/2006] [Indexed: 05/13/2023]
Abstract
RF heating of solid-state biological samples is known to be a destabilizing factor in high-field NMR experiments that shortens the sample lifetime by continuous dehydration during the high-power cross-polarization and decoupling pulses. In this work, we describe specially designed, large volume, low-E 15N-1H solid-state NMR probes developed for 600 and 900 MHz PISEMA studies of dilute membrane proteins oriented in hydrated and dielectrically lossy lipid bilayers. The probes use an orthogonal coil design in which separate resonators pursue their own aims at the respective frequencies, resulting in a simplified and more efficient matching network. Sample heating at the 1H frequency is minimized by a loop-gap resonator which produces a homogeneous magnetic field B1 with low electric field E. Within the loop-gap resonator, a multi-turn solenoid closely matching the shape of the sample serves as an efficient observe coil. We compare power dissipation in a typical lossy bilayer sample in the new low-E probe and in a previously reported 15N-1H probe which uses a double-tuned 4-turn solenoid. RF loss in the sample is measured in each probe by observing changes in the 1H 360 degrees pulse lengths. For the same values of 1H B1 field, sample heating in the new probe was found to be smaller by an order of magnitude. Applications of the low-E design to the PISEMA study of membrane proteins in their native hydrated bilayer environment are demonstrated at 600 and 900 MHz.
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Affiliation(s)
- Peter L Gor'kov
- National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.
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