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Simion A, Schubeis T, Le Marchand T, Vasilescu M, Pintacuda G, Lesage A, Filip C. Heteronuclear decoupling with Rotor-Synchronized Phase-Alternated Cycles. J Chem Phys 2022; 157:014202. [DOI: 10.1063/5.0098135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A new heteronuclear decoupling pulse sequence is introduced, dubbed ROtor-Synchronized Phase-Alternated Cycles (ROSPAC). It is based on a partial refocusing of the coherences (spin operator products, or cross-terms)1,2 responsible for transverse spin-polarization dephasing, on the irradiation of a large pattern of radio-frequencies, and on a significant minimization of the cross-effects implying 1H chemical-shift anisotropy. Decoupling efficiency is analyzed by numerical simulations and experiments, and compared to that of established decoupling sequences (swept-frequency TPPM, TPPM, SPINAL, rCWApa, and RS-HEPT). It was found that ROSPAC offers good 1H offset robustness for a large range of chemical shifts and low radio-frequency (RF) powers, and performs very well in the ultra-fast MAS regime, where it is almost independent from RF power and permits it to avoid rotary-resonance recoupling conditions ( ). It has the advantage that only the pulse lengths require optimization, and has a low duty cycle in the pulsed decoupling regime. The efficiency of the decoupling sequence is demonstrated on a model microcrystalline sample of the model protein domain GB1 at 100 kHz MAS at 18.8 T.
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Affiliation(s)
| | | | | | | | | | - Anne Lesage
- Laboratoire de Stereochimie, Ecole Normale Superieure, FRANCE
| | - Claudiu Filip
- National Institute for Research and Development of Isotopic and Molecular Technologies, Romania
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Wi S, Kim C, Schurko R, Frydman L. Adiabatic sweep cross-polarization magic-angle-spinning NMR of half-integer quadrupolar spins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 277:131-142. [PMID: 28285143 DOI: 10.1016/j.jmr.2017.02.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/26/2017] [Accepted: 02/28/2017] [Indexed: 06/06/2023]
Abstract
The use of frequency-swept radiofrequency (rf) pulses for enhancing signals in the magic-angle spinning (MAS) spectra of half-integer quadrupolar nuclides was explored. The broadband adiabatic inversion cross-polarization magic-angle spinning (BRAIN-CPMAS) method, involving an adiabatic inversion pulse on the S-channel and a simultaneous rectangular spin-lock pulse on the I-channel (1H), was applied to I(1/2)→S(3/2) systems. Optimal BRAIN-CPMAS matching conditions were found to involve low rf pulse strengths for both the I- and S-spin channels. At these low and easily attainable rf field strengths, level-crossing events among the energy levels |3/2〉,|1/2〉,|-1/2〉,|-3/2〉 that are known to complicate the CPMAS of quadrupolar nuclei, are mostly avoided. Zero- and double-quantum polarization transfer modes, akin to those we have observed for I(1/2)→S(1/2) polarization transfers, were evidenced by these analyses even in the presence of the quadrupolar interaction. 1H-23Na and 1H-11B BRAIN-CPMAS conditions were experimentally explored on model compounds by optimizing the width of the adiabatic sweep, as well as the rf pulse powers of the 1H and 23Na/11B channels, for different MAS rates. The experimental data obtained on model compounds containing spin-3/2 nuclides, matched well predictions from numerical simulations and from an average Hamiltonian theory model. Extensions to half-integer spin nuclides with higher spins and potential applications of this BRAIN-CPMAS approach are discussed.
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Affiliation(s)
- Sungsool Wi
- National High Magnetic Field Laboratory, Tallahassee, Florida 32304, USA.
| | - Chul Kim
- Department of Chemistry, Hannam University, Taejeon, 305811, South Korea
| | - Robert Schurko
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor N9B 3P4, Ontario, Canada
| | - Lucio Frydman
- National High Magnetic Field Laboratory, Tallahassee, Florida 32304, USA; Department of Chemical Physics, Weizmann Institute of Sciences, Rehovot 76100, Israel
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Wi S, Schurko R, Frydman L. 1H–2H cross-polarization NMR in fast spinning solids by adiabatic sweeps. J Chem Phys 2017; 146:104201. [DOI: 10.1063/1.4976980] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Sungsool Wi
- National High Magnetic Field Laboratory, Tallahassee, Florida 32304, USA
| | - Robert Schurko
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor N9B 3P4, Ontario, Canada
| | - Lucio Frydman
- National High Magnetic Field Laboratory, Tallahassee, Florida 32304, USA
- Department of Chemical Physics, Weizmann Institute of Sciences, Rehovot 76100, Israel
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4
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The plane-wave DFT investigations into the structure and the 11B solid-state NMR parameters of lithium fluorooxoborates. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.10.071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Equbal A, Basse K, Nielsen NC. Highly efficient19F heteronuclear decoupling in solid-state NMR spectroscopy using supercycled refocused-CW irradiation. Phys Chem Chem Phys 2016; 18:30990-30997. [DOI: 10.1039/c6cp06574k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present heteronuclear19F refocused CW (rCW) decoupling pulse sequences for solid-state magic-angle-spinning NMR applications.
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Affiliation(s)
- Asif Equbal
- Center for Insoluble Protein Structures (inSPIN)
- Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry
- Aarhus University
- Denmark
| | - Kristoffer Basse
- Center for Insoluble Protein Structures (inSPIN)
- Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry
- Aarhus University
- Denmark
| | - Niels Chr. Nielsen
- Center for Insoluble Protein Structures (inSPIN)
- Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry
- Aarhus University
- Denmark
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Madhu PK. Heteronuclear Spin Decoupling in Solid-State Nuclear Magnetic Resonance: Overview and Outlook. Isr J Chem 2013. [DOI: 10.1002/ijch.201300097] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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7
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Bräuniger T, Jansen M. Solid-state NMR Spectroscopy of Quadrupolar Nuclei in Inorganic Chemistry. Z Anorg Allg Chem 2013. [DOI: 10.1002/zaac.201300102] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Vinther JM, Khaneja N, Nielsen NC. Robust and efficient 19F heteronuclear dipolar decoupling using refocused continuous-wave rf irradiation. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 226:88-92. [PMID: 23220184 DOI: 10.1016/j.jmr.2012.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 11/04/2012] [Accepted: 11/07/2012] [Indexed: 06/01/2023]
Abstract
Refocused continuous wave (rCW) decoupling is presented as an efficient and robust means to obtain well-resolved magic-angle-spinning solid-state NMR spectra of low-γ spins, such as (13)C dipolar coupled to fluorine. The rCW decoupling sequences, recently introduced for (1)H decoupling, are very robust towards large isotropic and anisotropic shift ranges as often encountered for (19)F spins. In rCW decoupling, the so-called refocusing pulses inserted into the CW irradiation eliminate critical residual second- and third-order dipolar coupling and dipolar-coupling against chemical shielding anisotropy cross-terms in the effective Hamiltonian through time-reversal (i.e. refocusing). As important additional assets, the rCW decoupling sequences are robust towards variations in rf amplitudes, operational at low to high spinning speeds, and easy to set-up for optimal performance experimentally. These aspects are demonstrated analytically/numerically and experimentally in comparison to state-of-the-art decoupling sequences such as TPPM, SPINAL-64, and frequency-swept variants of these.
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Affiliation(s)
- Joachim M Vinther
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Aarhus C, Denmark
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Full differentiation and assignment of boron species in the electrolytes Li2B6O9F2 and Li2B3O4F3 by solid-state 11B NMR spectroscopy. J SOLID STATE CHEM 2012. [DOI: 10.1016/j.jssc.2012.05.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Chandran CV, Hempel G, Bräuniger T. 19F-decoupling of half-integer spin quadrupolar nuclei in solid-state NMR: application of frequency-swept decoupling methods. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2011; 40:84-87. [PMID: 21856132 DOI: 10.1016/j.ssnmr.2011.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Revised: 07/28/2011] [Accepted: 07/29/2011] [Indexed: 05/31/2023]
Abstract
In solid-state NMR studies of minerals and ion conductors, quadrupolar nuclei like (7)Li, (23)Na or (133)Cs are frequently situated in close proximity to fluorine, so that application of (19)F decoupling is beneficial for spectral resolution. Here, we compare the decoupling efficiency of various multi-pulse decoupling sequences by acquiring (19)F-decoupled (23)Na-NMR spectra of cryolite (Na(3)AlF(6)). Whereas the MAS spectrum is only marginally affected by application of (19)F decoupling, the 3Q-filtered (23)Na signal is very sensitive to it, as the de-phasing caused by the dipolar interaction between sodium and fluorine is three-fold magnified. Experimentally, we find that at moderate MAS speeds, the decoupling efficiencies of the frequency-swept decoupling schemes SW(f)-TPPM and SW(f)-SPINAL are significantly better than the conventional TPPM and SPINAL sequences. The frequency-swept sequences are therefore the methods of choice for efficient decoupling of quadrupolar nuclei with half-integer spin from fluorine.
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Affiliation(s)
- C Vinod Chandran
- Max-Planck-Institute of Solid-State Research, Stuttgart, Germany
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Augustine C, Kurur ND. Supercycled SW(f)-TPPM sequence for heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 209:156-160. [PMID: 21306928 DOI: 10.1016/j.jmr.2011.01.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2010] [Revised: 12/29/2010] [Accepted: 01/07/2011] [Indexed: 05/30/2023]
Abstract
The performance of a supercycled SW(f)-TPPM sequence for heteronuclear dipolar decoupling in solid-state NMR is analyzed here. The decoupling performance of this sequence with respect to experimental parameters, such as, the phase angle, proton offset and MAS frequency is studied. A comparison is made with two other commonly used decoupling schemes in solid-state NMR namely, SPINAL-64 and SW(f)-TPPM, on a sample of U-¹³C-labeled tyrosine. Our results show that supercycled SW(f)-TPPM performs better than the former sequences. Also, numerical spin dynamics studies are presented which support the experimentally observed efficiency in the decoupling.
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Affiliation(s)
- Cyril Augustine
- Department of Chemistry, Indian Institute of Technology, New Delhi 110 016, India.
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Paul S, Vinod Chandran C, Bräuniger T, Madhu PK. Sweep direction and efficiency of the swept-frequency two pulse phase modulated scheme for heteronuclear dipolar-decoupling in solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 209:261-268. [PMID: 21345704 DOI: 10.1016/j.jmr.2011.01.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 01/14/2011] [Accepted: 01/19/2011] [Indexed: 05/30/2023]
Abstract
We present here a bimodal Floquet theoretical and experimental investigation of the direction of sweep in the swept-frequency two pulse phase modulated (SW(f)-TPPM) scheme used for heteronuclear dipolar decoupling in solid-state NMR. The efficiency of the decoupling turns out to be independent of the sweep direction.
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Affiliation(s)
- Subhradip Paul
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, India
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