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Schröder N, Bartalucci E, Wiegand T. Probing Noncovalent Interactions by Fast Magic-Angle Spinning NMR at 100 kHz and More. Chemphyschem 2024:e202400537. [PMID: 39129653 DOI: 10.1002/cphc.202400537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Revised: 06/19/2024] [Indexed: 08/13/2024]
Abstract
Noncovalent interactions are the basis for a large number of chemical and biological molecular-recognition processes, such as those occurring in supramolecular chemistry, catalysis, solid-state reactions in mechanochemistry, protein folding, protein-nucleic acid binding, and biomolecular phase separation processes. In this perspective article, some recent developments in probing noncovalent interactions by proton-detected solid-state Nuclear Magnetic Resonance (NMR) spectroscopy at Magic-Angle Spinning (MAS) frequencies of 100 kHz and more are reviewed. The development of MAS rotors with decreasing outer diameters, combined with the development of superconducting magnets operating at high static magnetic-field strengths up to 28.2 T (1200 MHz proton Larmor frequency) improves resolution and sensitivity in proton-detected solid-state NMR, which is the fundamental requirement for shedding light on noncovalent interactions in solids. The examples reported in this article range from protein-nucleic acid binding in large ATP-fueled motor proteins to a hydrogen-π interaction in a calixarene-lanthanide complex.
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Affiliation(s)
- Nina Schröder
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
| | - Ettore Bartalucci
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470, Mülheim/Ruhr, Germany
| | - Thomas Wiegand
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470, Mülheim/Ruhr, Germany
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Rai SK, Potnuru LR, Duong NT, Yamazaki T, Nangia AK, Nishiyama Y, Agarwal V. Probing Short-Range Interactions in Isostructural Hydrate and Perhydrate of Dabrafenib by Magic-Angle Spinning Solid-State NMR. Anal Chem 2024. [PMID: 39034533 DOI: 10.1021/acs.analchem.4c01317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Dabrafenib (DBF), an anticancer drug, exhibits isostructural properties in its hydrate (DBF⊃H2O) and perhydrate (DBF⊃H2O2) forms, as revealed by single-crystal X-ray diffraction. Despite the H2O and H2O2 solvent molecules occupying identical locations, the two polymorphs have different thermal behaviors. In general, determination of stoichiometry of H2O in the perhydrate crystals is difficult due to the presence of both H2O and H2O2 in the same crystal voids. This study utilizes magic-angle spinning (MAS) solid-state NMR (SSNMR) combined with gauge-included projector augmented wave calculations to characterize the influence of solvent molecules on the local environment in pseudopolymorphs. SSNMR experiments were employed to assign 1H, 13C, and 15N peaks and identify spectral differences in the isostructural pseudopolymorphs. Proton spectroscopy at fast MAS was used to identify and quantify H2O2/H2O in DBF⊃H2O2 (mixed hydrate/perhydrate). 1H-1H dipolar-coupling-based experiments were recruited to confirm the 3D molecular packing of solvent molecules in DBF⊃H2O and DBF⊃H2O2. Homonuclear (1H-1H) and heteronuclear (1H-14N) distance measurements, in conjunction with diffraction structures and optimized hydrogen atom positions by density functional theory, helped decipher local interactions of H2O2 with DBF and their geometry in DBF⊃H2O2. This integrated X-ray structure, quantum chemical calculations, and NMR study of pseudopolymorphs offer a practical approach to scrutinizing crystallized solvent interactions in the crystal lattice even without high-resolution crystal structures or artificial sample enrichment.
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Affiliation(s)
- Sunil K Rai
- Tata Institute of Fundamental Research Hyderabad, Hyderabad, Telangana 500046, India
| | - Lokeswara Rao Potnuru
- Tata Institute of Fundamental Research Hyderabad, Hyderabad, Telangana 500046, India
| | - Nghia Tuan Duong
- RIKEN-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Toshio Yamazaki
- RIKEN-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Ashwini K Nangia
- School of Chemistry, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Central University P.O., Hyderabad 500046, India
| | - Yusuke Nishiyama
- RIKEN-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
- JEOL Ltd., Musashino, Akishima, Tokyo 196-8558, Japan
| | - Vipin Agarwal
- Tata Institute of Fundamental Research Hyderabad, Hyderabad, Telangana 500046, India
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Yan Z, Zhao P, Yan X, Zhang R. Using Abundant 1H Polarization to Enhance the Sensitivity of Solid-State NMR Spectroscopy. J Phys Chem Lett 2024; 15:1866-1878. [PMID: 38343090 DOI: 10.1021/acs.jpclett.3c03532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Solid-state NMR spectroscopy has been playing a significant role in elucidating the structures and dynamics of materials and proteins at the atomic level for decades. As an extremely abundant nucleus with a very high gyromagnetic ratio, protons are widely present in most organic/inorganic materials. Thus, this Perspective highlights the advantages of proton detection at fast magic-angle spinning (MAS) and presents strategies to utilize and exhaust 1H polarization to achieve signal sensitivity enhancement of solid-state NMR spectroscopy, enabling substantial time savings and extraction of more structural and dynamics information per unit time. Those strategies include developing sensitivity-enhanced single-channel 1H multidimensional NMR spectroscopy, implementing multiple polarization transfer steps in each scan to enhance low-γ nuclei signals, and making full use of 1H polarization to obtain homonuclear and heteronuclear chemical shift correlation spectra in a single experiment. Finally, outlooks and perspectives are provided regarding the challenges and future for the further development of sensitivity-enhanced proton-based solid-state NMR spectroscopy.
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Affiliation(s)
- Zhiwei Yan
- South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter (SESM), South China University of Technology, Guangzhou 510640, P. R. China
| | - Peizhi Zhao
- South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter (SESM), South China University of Technology, Guangzhou 510640, P. R. China
| | - Xiaojing Yan
- South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter (SESM), South China University of Technology, Guangzhou 510640, P. R. China
| | - Rongchun Zhang
- South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter (SESM), South China University of Technology, Guangzhou 510640, P. R. China
- Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China
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Luder DJ, Terefenko N, Sun Q, Eckert H, Mück-Lichtenfeld C, Kehr G, Erker G, Wiegand T. Polar covalent apex-base bonding in borapyramidanes probed by solid-state NMR and DFT calculations. Chemistry 2024; 30:e202303701. [PMID: 38078510 DOI: 10.1002/chem.202303701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Indexed: 01/04/2024]
Abstract
Pyramidane molecules have attracted chemists for many decades due to their regular shape, high symmetry and their correspondence in the macroscopic world. Recently, experimental access to a number of examples has been reported, in particular the rarely reported square pyramidal bora[4]pyramidanes. To describe the bonding situation of the nonclassical structure of pyramidanes, we present solid-state Nuclear Magnetic Resonance (NMR) as a versatile tool for deciphering such bonding properties for three now accessible bora[4]pyramidane and dibora[5]pyramidane molecules. 11 B solid-state NMR spectra indicate that the apical boron nuclei in these compounds are strongly shielded (around -50 ppm vs. BF3 -Et2 O complex) and possess quadrupolar coupling constants of less than 0.9 MHz pointing to a rather high local symmetry. 13 C-11 B spin-spin coupling constants have been explored as a measure of the bond covalency in the borapyramidanes. While the carbon-boron bond to the -B(C6 F5 )2 substituents of the base serves as an example for a classical covalent 2-center-2-electron (2c-2e) sp2 -carbon-sp2 -boron σ-bond with 1 J(13 C-11 B) coupling constants in the order of 75 Hz, those of the boron(apical)-carbon(basal) bonds in the pyramid are too small to measure. These results suggest that these bonds have a strongly ionic character, which is also supported by quantum-chemical calculations.
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Affiliation(s)
- Dominique J Luder
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
- Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zürich, Switzerland
| | - Nicole Terefenko
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
| | - Qiu Sun
- Organische Chemie, University of Münster, Corrensstr. 36, 48149, Münster, Germany
| | - Hellmut Eckert
- Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP 13566-590, Brazil
- Institut für Physikalische Chemie, University of Münster, Corrensstr. 30, 48149, Münster, Germany
| | | | - Gerald Kehr
- Organische Chemie, University of Münster, Corrensstr. 36, 48149, Münster, Germany
| | - Gerhard Erker
- Organische Chemie, University of Münster, Corrensstr. 36, 48149, Münster, Germany
| | - Thomas Wiegand
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470, Mülheim, Germany
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Hareendran C, Shaligram PS, Gonnade R, Ajithkumar TG. A solid-state NMR method for characterization of pharmaceutical eutectics. Phys Chem Chem Phys 2024; 26:3800-3803. [PMID: 38240042 DOI: 10.1039/d3cp05615e] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Pharmaceutical eutectics are extremely useful for designing formulations, and currently, there are no techniques other than differential scanning calorimetry (DSC) that can confirm their formation. In this study, we demonstrate that 1H fast magic angle spinning (MAS) solid-state NMR (SSNMR) experiments can confirm the formation of eutectics by detecting their intermolecular hydrogen bonding interactions.
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Affiliation(s)
- Chaithanya Hareendran
- Central NMR facility and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Parth S Shaligram
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
| | - Rajesh Gonnade
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India
| | - T G Ajithkumar
- Central NMR facility and Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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Ramachandran M, Anandababu A, Al Souwaileh A, Anandan S. Selective turn-on sensing of adenosine diphosphate and phosphate anions by ruthenium (II) polypyridine anchored p-tert-butylcalix[4]arene platform. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 305:123483. [PMID: 37804708 DOI: 10.1016/j.saa.2023.123483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 09/23/2023] [Accepted: 09/30/2023] [Indexed: 10/09/2023]
Abstract
BACKGROUND Nucleoside polyphosphate (NPP) anions are important for enzymatic activity and should be monitored by scientists in industry and medicine. By elucidating enzyme kinetics and processes, it aids in the discovery of effective inhibitors and activators. Nucleoside polyphosphate (NPP) anions are used by kinases, GTPases, and glycosyltransferases (GTs). Phosphorylation of certain amino acid residues (Ser, Thr, and Tyr) on proteins requires the breakdown of ATP by protein kinases, which produces ADP. Protein kinases, breakdown of ATP, and NPP are the focus of oncology drug development because the aberrant control of kinase activity is a common cause of cancer. RESULTS However, a discriminative turn-on fluorescent property is exhibited by non-fluorescent p-tertbutylcalix[4]arene modified 1,2,3-triazole containing bis-ruthenium polypyridyl complex (RL) upon the addition of phosphate anions such as (dihydrogen pyrophosphate (H2P2O72-) and dihydrogen phosphate (H2PO4-)) in CH3CN solvent and Adenosine Diphosphate (ADP) in CH3CN/HEPES (pH = 7.4) buffer (9/1, v/v). The probe RL shows a better-recognizing ability with pyrophosphate anion (H2P2O72-) than dihydrogen phosphate anion (H2PO4-). With H2P2O72- and H2PO4- anions, the RL detection limit was calculated to be as low as 83 nM and 198 nM, respectively. SIGNIFICANCE The calix[4]arene macrocycle's excellent size and binding cone conformation make it a good host-guest interface for the pyrophosphate anion and ADP. The bis-ruthenium polypyridyl complex's connection to the p-tertbutyl calix[4]arene moiety creates the ADP selectivity turn-on sensor. When moving from mono-nuclear to bi-nuclear ruthenium complex anchored on p-tertbutyl calix[4]arene, the probe can differentiate ADP, ATP, and AMP. Furthermore, this platform is a great resource for creating devices to simultaneously assess phosphate anions in environmental samples.
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Affiliation(s)
- Mohanraj Ramachandran
- Nanomaterials & Solar Energy Conversion Lab, Department of Chemistry, National Institute of Technology, Tiruchirappalli 620015, India
| | - Ambigapathi Anandababu
- Nanomaterials & Solar Energy Conversion Lab, Department of Chemistry, National Institute of Technology, Tiruchirappalli 620015, India
| | - Abdullah Al Souwaileh
- Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
| | - Sambandam Anandan
- Nanomaterials & Solar Energy Conversion Lab, Department of Chemistry, National Institute of Technology, Tiruchirappalli 620015, India.
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Silva IDA, Bartalucci E, Bolm C, Wiegand T. Opportunities and Challenges in Applying Solid-State NMR Spectroscopy in Organic Mechanochemistry. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2304092. [PMID: 37407000 DOI: 10.1002/adma.202304092] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 06/12/2023] [Accepted: 06/28/2023] [Indexed: 07/07/2023]
Abstract
In recent years it is shown that mechanochemical strategies can be beneficial in directed conversions of organic compounds. Finding new reactions proved difficult, and due to the lack of mechanistic understanding of mechanochemical reaction events, respective efforts have mostly remained empirical. Spectroscopic techniques are crucial in shedding light on these questions. In this overview, the opportunities and challenges of solid-state nuclear magnetic resonance (NMR) spectroscopy in the field of organic mechanochemistry are discussed. After a brief discussion of the basics of high-resolution solid-state NMR under magic-angle spinning (MAS) conditions, seven opportunities for solid-state NMR in the field of organic mechanochemistry are presented, ranging from ex situ approaches to structurally elucidated reaction products obtained by milling to the potential and limitations of in situ solid-state NMR approaches. Particular strengths of solid-state NMR, for instance in differentiating polymorphs, in NMR-crystallographic structure-determination protocols, or in detecting weak noncovalent interactions in molecular-recognition events employing proton-detected solid-state NMR experiments at fast MAS frequencies, are discussed.
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Affiliation(s)
| | - Ettore Bartalucci
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470, Mülheim/Ruhr, Germany
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
| | - Carsten Bolm
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Thomas Wiegand
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470, Mülheim/Ruhr, Germany
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany
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8
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Lopatik N, De A, Paasch S, Schneemann A, Brunner E. High-field and fast-spinning 1H MAS NMR spectroscopy for the characterization of two-dimensional covalent organic frameworks. Phys Chem Chem Phys 2023; 25:30237-30245. [PMID: 37921503 DOI: 10.1039/d3cp04144a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
Two-dimensional (2D) materials, like 2D covalent organic frameworks (COFs), have been attracting increasing research interest. They are usually obtained as polycrystalline powders. Solid-state NMR spectroscopy is capable of delivering structural information about such materials. Previous studies have applied, for example, 13C cross-polarization magic angle spinning (CP MAS) NMR experiments to characterize 2D COFs. Herein, we demonstrate the usefulness of high-field and fast-spinning 1H MAS NMR spectroscopy to resolve and quantify the signals of different 1H species within 2D COFs, including the edge sites and/or defects. Moreover, 1H-13C heteronuclear correlation (HETCOR) spectroscopy has also been applied and can provide improved resolution to obtain further information about stacking effects as well as edge sites/defects.
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Affiliation(s)
- Nikolaj Lopatik
- Chair of Bioanalytical Chemistry, Faculty of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany.
| | - Ankita De
- Chair of Inorganic Chemistry I, Faculty of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany
| | - Silvia Paasch
- Chair of Bioanalytical Chemistry, Faculty of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany.
| | - Andreas Schneemann
- Chair of Inorganic Chemistry I, Faculty of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany
| | - Eike Brunner
- Chair of Bioanalytical Chemistry, Faculty of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany.
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Czernek J, Brus J, Czerneková V, Kobera L. Quantifying the Intrinsic Strength of C-H⋯O Intermolecular Interactions. Molecules 2023; 28:molecules28114478. [PMID: 37298953 DOI: 10.3390/molecules28114478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 05/27/2023] [Accepted: 05/29/2023] [Indexed: 06/12/2023] Open
Abstract
It has been recognized that the C-H⋯O structural motif can be present in destabilizing as well as highly stabilizing intermolecular environments. Thus, it should be of interest to describe the strength of the C-H⋯O hydrogen bond for constant structural factors so that this intrinsic strength can be quantified and compared to other types of interactions. This description is provided here for C2h-symmetric dimers of acrylic acid by means of the calculations that employ the coupled-cluster theory with singles, doubles, and perturbative triples [CCSD(T)] together with an extrapolation to the complete basis set (CBS) limit. Dimers featuring the C-H⋯O and O-H⋯O hydrogens bonds are carefully investigated in a wide range of intermolecular separations by the CCSD(T)/CBS approach, and also by the symmetry-adapted perturbation theory (SAPT) method, which is based on the density-functional theory (DFT) treatment of monomers. While the nature of these two types of hydrogen bonding is very similar according to the SAPT-DFT/CBS calculations and on the basis of a comparison of the intermolecular potential curves, the intrinsic strength of the C-H⋯O interaction is found to be about a quarter of its O-H⋯O counterpart that is less than one might anticipate.
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Affiliation(s)
- Jiří Czernek
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovsky Square 2, 162 00 Prague, Czech Republic
| | - Jiří Brus
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovsky Square 2, 162 00 Prague, Czech Republic
| | - Vladimíra Czerneková
- Institute of Physics, Czech Academy of Science, Na Slovance 2, 182 21 Prague, Czech Republic
| | - Libor Kobera
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovsky Square 2, 162 00 Prague, Czech Republic
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Tatman BP, Franks WT, Brown SP, Lewandowski JR. Nuclear spin diffusion under fast magic-angle spinning in solid-state NMR. J Chem Phys 2023; 158:2890210. [PMID: 37171196 DOI: 10.1063/5.0142201] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 04/10/2023] [Indexed: 05/13/2023] Open
Abstract
Solid-state nuclear spin diffusion is the coherent and reversible process through which spin order is transferred via dipolar couplings. With the recent increases in magic-angle spinning (MAS) frequencies and magnetic fields becoming routinely applied in solid-state nuclear magnetic resonance, understanding how the increased 1H resolution obtained affects spin diffusion is necessary for interpretation of several common experiments. To investigate the coherent contributions to spin diffusion with fast MAS, we have developed a low-order correlation in Liouville space model based on the work of Dumez et al. (J. Chem. Phys. 33, 224501, 2010). Specifically, we introduce a new method for basis set selection, which accounts for the resonance-offset dependence at fast MAS. Furthermore, we consider the necessity of including chemical shift, both isotropic and anisotropic, in the modeling of spin diffusion. Using this model, we explore how different experimental factors change the nature of spin diffusion. Then, we show case studies to exemplify the issues that arise in using spin diffusion techniques at fast spinning. We show that the efficiency of polarization transfer via spin diffusion occurring within a deuterated and 100% back-exchanged protein sample at 60 kHz MAS is almost entirely dependent on resonance offset. We additionally identify temperature-dependent magnetization transfer in beta-aspartyl L-alanine, which could be explained by the influence of an incoherent relaxation-based nuclear Overhauser effect.
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Affiliation(s)
- Ben P Tatman
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - W Trent Franks
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Steven P Brown
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Józef R Lewandowski
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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