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Kobayashi T, Nishiyama Y, Pandey MK. Determination of the mutual orientation between proton CSA tensors mediated through band-selective 1H- 1H recoupling under fast MAS. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2023; 125:101874. [PMID: 37216831 DOI: 10.1016/j.ssnmr.2023.101874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 05/24/2023]
Abstract
The mutual orientation of nuclear spin interaction tensors provides critical information on the conformation and arrangement of molecules in chemicals, materials, and biological systems at an atomic level. Proton is a ubiquitous and important element in a variety of substances, and its NMR is highly sensitive due to their virtually 100% natural abundance and large gyromagnetic ratio. Nevertheless, the measurement of mutual orientation between the 1H CSA tensors has remained largely untouched in the past due to strong 1H-1H homonuclear interactions in a dense network of protons. In this study, we have developed a proton-detected 3D 1H CSA/1H CSA/1H CS correlation method that utilizes three techniques to manage homonuclear interactions, namely fast magic-angle spinning, windowless C-symmetry-based CSA recoupling (windowless-ROCSA), and a band-selective 1H-1H polarization transfer. The asymmetric 1H CSA/1H CSA correlated powder patterns produced by the C-symmetry-based methods are highly sensitive to the sign and asymmetry parameter of the 1H CSA, and the Euler angle β as compared to the symmetric pattern obtained by the existing γ-encoded R-symmetry-based CSA/CSA correlation methods and allows a larger spectral area for data fitting. These features are beneficial for determining the mutual orientation between the nuclear spin interaction tensors with improved accuracy.
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Affiliation(s)
- Takeshi Kobayashi
- U.S. DOE, Ames National Laboratory, Iowa State University, Ames, IA, 50011-3020, USA.
| | | | - Manoj Kumar Pandey
- Indian Institute of Technology (IIT) Ropar, Rupnagar, Punjab, 140001, India
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2
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Sehrawat N, Nehra E, Kumar Rohilla K, Kobayashi T, Nishiyama Y, Kumar Pandey M. Determination of the relative orientation between 15N- 1H dipolar coupling and 1H chemical shift anisotropy tensors under fast MAS solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 350:107428. [PMID: 37018911 DOI: 10.1016/j.jmr.2023.107428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 03/15/2023] [Accepted: 03/24/2023] [Indexed: 05/10/2023]
Abstract
In this work, we have proposed a proton-detected three-dimensional (3D) 15N-1H dipolar coupling (DIP)/1H chemical shift anisotropy (CSA)/1H chemical shift (CS) correlation experiment to measure the relative orientation between the 15N-1H dipolar coupling and the 1H CSA tensors under fast magic angle spinning (MAS) solid-state NMR. In the 3D correlation experiment, the 15N-1H dipolar coupling and 1H CSA tensors are recoupled using our recently developed windowless C-symmetry-based C331-ROCSA (recoupling of chemical shift anisotropy) DIPSHIFT and C331-ROCSA pulse-based methods, respectively. The 2D 15N-1H DIP/1H CSA powder lineshapes extracted using the proposed 3D correlation method are shown to be sensitive to the sign and asymmetry of the 1H CSA tensor, a feature that allows the determination of the relative orientation between the two correlating tensors with improved accuracy. The experimental method developed in this study is demonstrated on a powdered U-15N L-Histidine.HCl·H2O sample.
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Affiliation(s)
- Neelam Sehrawat
- Indian Institute of Technology (IIT) Ropar, Rupnagar, Punjab 140001, India
| | - Ekta Nehra
- Indian Institute of Technology (IIT) Ropar, Rupnagar, Punjab 140001, India
| | | | - Takeshi Kobayashi
- U.S. DOE, Ames Laboratory, Iowa State University, Ames, IA 50011-3020, United States
| | - Yusuke Nishiyama
- RIKEN-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan; JEOL Ltd., Musashino, Akishima, Tokyo 196-8558, Japan.
| | - Manoj Kumar Pandey
- Indian Institute of Technology (IIT) Ropar, Rupnagar, Punjab 140001, India.
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Southern SA, Liu DJ, Chatterjee P, Li Y, Perras FA. 1H chemical shift anisotropy: a high sensitivity solid-state NMR dynamics probe for surface studies? Phys Chem Chem Phys 2023; 25:5348-5360. [PMID: 36399032 DOI: 10.1039/d2cp04406d] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Dynamics play significant roles in chemistry and biochemistry-molecular motions impact both large- and small-scale chemical reactions in addition to biochemical processes. In many systems, including heterogeneous catalysts, the characterization of dynamics remains a challenge. The most common approaches involve the solid-state NMR measurement of anisotropic interactions, in particular 2H quadrupolar coupling and 1H-X dipolar coupling, which generally require isotope enrichment. Due to the high sensitivity of 1H NMR, 1H chemical shift anisotropy (CSA) is a particularly enticing, and underexplored, dynamics probe. We carried out 1H CSA and 1H-13C dipolar coupling measurements in a series of model supported complexes to understand how 1H CSA can be leveraged to gain dynamic information for heterogeneous catalysts. Mathematical descriptions are given for the dynamic averaging of the CSA tensor, and its dependence on orientation and asymmetry. The variability of the orientation of the tensor in the molecular frame, in addition to its magnitude and asymmetry, negatively impacts attempts to extract quantitative dynamic information. Nevertheless, 1H CSA measurements can reveal useful qualitative insights into the motions of a particularly dilute site, such as from a surface species.
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Affiliation(s)
- Scott A Southern
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA.
| | - Da-Jiang Liu
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA.
| | - Puranjan Chatterjee
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA. .,Department of Chemistry, Iowa State University, Ames, IA 50014, USA
| | - Yuting Li
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA.
| | - Frédéric A Perras
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA.
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Nishiyama Y, Hou G, Agarwal V, Su Y, Ramamoorthy A. Ultrafast Magic Angle Spinning Solid-State NMR Spectroscopy: Advances in Methodology and Applications. Chem Rev 2023; 123:918-988. [PMID: 36542732 PMCID: PMC10319395 DOI: 10.1021/acs.chemrev.2c00197] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Solid-state NMR spectroscopy is one of the most commonly used techniques to study the atomic-resolution structure and dynamics of various chemical, biological, material, and pharmaceutical systems spanning multiple forms, including crystalline, liquid crystalline, fibrous, and amorphous states. Despite the unique advantages of solid-state NMR spectroscopy, its poor spectral resolution and sensitivity have severely limited the scope of this technique. Fortunately, the recent developments in probe technology that mechanically rotate the sample fast (100 kHz and above) to obtain "solution-like" NMR spectra of solids with higher resolution and sensitivity have opened numerous avenues for the development of novel NMR techniques and their applications to study a plethora of solids including globular and membrane-associated proteins, self-assembled protein aggregates such as amyloid fibers, RNA, viral assemblies, polymorphic pharmaceuticals, metal-organic framework, bone materials, and inorganic materials. While the ultrafast-MAS continues to be developed, the minute sample quantity and radio frequency requirements, shorter recycle delays enabling fast data acquisition, the feasibility of employing proton detection, enhancement in proton spectral resolution and polarization transfer efficiency, and high sensitivity per unit sample are some of the remarkable benefits of the ultrafast-MAS technology as demonstrated by the reported studies in the literature. Although the very low sample volume and very high RF power could be limitations for some of the systems, the advantages have spurred solid-state NMR investigation into increasingly complex biological and material systems. As ultrafast-MAS NMR techniques are increasingly used in multidisciplinary research areas, further development of instrumentation, probes, and advanced methods are pursued in parallel to overcome the limitations and challenges for widespread applications. This review article is focused on providing timely comprehensive coverage of the major developments on instrumentation, theory, techniques, applications, limitations, and future scope of ultrafast-MAS technology.
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Affiliation(s)
- Yusuke Nishiyama
- JEOL Ltd., Akishima, Tokyo196-8558, Japan
- RIKEN-JEOL Collaboration Center, Yokohama, Kanagawa230-0045, Japan
| | - Guangjin Hou
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian116023, China
| | - Vipin Agarwal
- Tata Institute of Fundamental Research, Sy. No. 36/P, Gopanpally, Hyderabad500 046, India
| | - Yongchao Su
- Analytical Research and Development, Merck & Co., Inc., Rahway, New Jersey07065, United States
| | - Ayyalusamy Ramamoorthy
- Biophysics, Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, Michigan41809-1055, United States
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Brouwer DH, Mikolajewski JG. A combined solid-state NMR and quantum chemical calculation study of hydrogen bonding in two forms of α-d-glucose. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2023; 123:101848. [PMID: 36584544 DOI: 10.1016/j.ssnmr.2022.101848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 12/07/2022] [Accepted: 12/13/2022] [Indexed: 06/17/2023]
Abstract
Hydrogen bonding plays an important role in the structure and function of a wide range of materials. Solid-state 1H nuclear magnetic resonance (NMR) spectroscopy provides a very sensitive tool to investigate the local structure of hydrogen atoms involved in hydrogen bonding. While there is extensive 1H solid-state NMR data on O-H - - O hydrogen bonding in solid carboxylic acids, there has been no systematic 1H solid-state NMR studies of hydroxyl groups in carbohydrates (and hydroxyl groups in general). With a view to studying the hydrogen bonding in more complex materials such as cellulose polymorphs, we carried out a detailed solid-state 1H NMR investigation of the model compounds α-d-glucose and α-d-glucose monohydrate. Through a combination of fast magic-angle spinning (MAS), combined rotation and multiple pulse spectroscopy (CRAMPS), and two-dimensional (2D) correlation experiments carried out at ultrahigh magnetic fields, it was possible to assign all of the aliphatic (CH), hydroxyl (OH), and water (H2O) 1H chemical shifts in both forms of α-d-glucose. Plane-wave DFT calculations were employed to improve the hydrogen atom positions for α-d-glucose monohydrate and to calculate 1H chemical shifts, providing additional support for the experimentally determined peak assignments. Finally, the relationship between the hydroxyl 1H chemical shifts and their hydrogen bonding geometry was investigated and compared to the well-established relationship for carboxylic acid protons.
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Affiliation(s)
- Darren H Brouwer
- Department of Chemistry, Redeemer University, Ancaster, ON, L9K 1J4, Canada.
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Kobayashi T, Perras FA, Nishiyama Y. Determination of the chemical shift tensor anisotropy and asymmetry of strongly dipolar coupled protons under fast MAS. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2021; 114:101743. [PMID: 34153880 DOI: 10.1016/j.ssnmr.2021.101743] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 06/01/2021] [Accepted: 06/01/2021] [Indexed: 06/13/2023]
Abstract
Orientationally-dependent interactions such as dipolar coupling, quadrupolar coupling, and chemical shift anisotropy (CSA) contain a wealth of spatial information that can be used to elucidate molecular conformations and dynamics. To determine the sign of the chemical shift tensor anisotropy parameter (δaniso), both the |m| = 1 and |m| = 2 components of the CSA need to be symmetry allowed, while the recoupling of the |m| = 1 term is accompanied with the reintroduction of homonuclear dipolar coupling components. Therefore, previously suggested sequences which solely recouple the |m| = 2 term cannot determine the sign a 1H's δaniso in a densely-coupled network. In this study, we demonstrate the CSA recoupling of strongly dipolar coupled 1H spins using the Cnn1(9003601805400360180900) sequence. This pulse scheme recouples both the |m| = 1 and |m| = 2 CSA terms but the scaling factors for the homonuclear dipolar coupling terms are zeroed. Consequently, the sequence is sensitive to the sign of δaniso but is not influenced by homonuclear dipolar interactions.
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Affiliation(s)
- Takeshi Kobayashi
- U.S. DOE, Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States.
| | - Frédéric A Perras
- U.S. DOE, Ames Laboratory, Iowa State University, Ames, IA, 50011-3020, United States
| | - Yusuke Nishiyama
- RIKEN-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa, 230-0045, Japan; JEOL RESONANCE Inc., Musashino, Akishima, Tokyo, 196-8558, Japan
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7
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Potnuru LR, Duong NT, Sasank B, Raran-Kurussi S, Nishiyama Y, Agarwal V. Selective 1H- 1H recoupling via symmetry sequences in fully protonated samples at fast magic angle spinning. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 328:107004. [PMID: 34049237 DOI: 10.1016/j.jmr.2021.107004] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 05/09/2021] [Accepted: 05/10/2021] [Indexed: 05/08/2023]
Abstract
Proton-detected solid-state NMR at fast Magic Angle Spinning (MAS) is becoming the norm to characterize molecules. Routinely 1H-1H and 1H-X dipolar couplings are used to characterize the structure and dynamics of molecules. Selective proton recoupling techniques are emerging as a method for structural characterization via estimation of qualitative and quantitative distances. In the present study, we demonstrate through numerical simulations and experiments that the well-characterized CNvn sequences can also be tailored for selective recoupling of proton spins by employing C elements of the type (β)Φ(4β)Φ+π(3β)Φ. Herein, several CNvn sequences were examined through numerical simulations and experiments. C614 recoupling sequence with a modified POST-element ((β)Φ(4β)Φ+π(3β)Φ) shows selective polarization transfer efficiencies on the order of 40-50% between various proton spin pairs in fully protonated samples at rf amplitudes ranging from 0.3 to 0.8 times the MAS frequency. These selective recoupling sequences have been labeled as frequency-selective-CNvn sequences. The extent of selectivity, polarization transfer efficiency and the feasibility of experimentally measuring proton-proton distances in fully protonated samples are explored here. The development of efficient and robust selective 1H-1H recoupling experiments is required to structurally characterize molecules without artificial isotope enrichment or the need for diffracting crystals.
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Affiliation(s)
- Lokeswara Rao Potnuru
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad, Sy. No. 36/P, Gopanpally, Ranga Reddy District, Hyderabad 500 107, India
| | - Nghia Tuan Duong
- Nano-Crystallography Unit, RIKEN-JEOL Collaboration Center, Yokohama, Kanagawa 230-0045, Japan
| | - Budaraju Sasank
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad, Sy. No. 36/P, Gopanpally, Ranga Reddy District, Hyderabad 500 107, India; Department of Physical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Mohali 140306, India
| | - Sreejith Raran-Kurussi
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad, Sy. No. 36/P, Gopanpally, Ranga Reddy District, Hyderabad 500 107, India
| | - Yusuke Nishiyama
- Nano-Crystallography Unit, RIKEN-JEOL Collaboration Center, Yokohama, Kanagawa 230-0045, Japan; JEOL RESONANCE Inc., Musashino, Akishima, Tokyo 196-8558, Japan.
| | - Vipin Agarwal
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad, Sy. No. 36/P, Gopanpally, Ranga Reddy District, Hyderabad 500 107, India.
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Perras FA, Paterson AL, Kobayashi T. Phase-sensitive γ-encoded recoupling of heteronuclear dipolar interactions and 1H chemical shift anisotropy. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2021; 111:101712. [PMID: 33450713 DOI: 10.1016/j.ssnmr.2020.101712] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/18/2020] [Accepted: 12/19/2020] [Indexed: 06/12/2023]
Abstract
γ-encoded recoupling sequences are known to produce strong amplitude modulations that lead to sharp doublets when Fourier transformed. These doublets depend very little on the recoupled tensor asymmetry and thus enable for the straightforward determination of dynamic order parameters. It can, however, be difficult to measure small anisotropies, or small order parameters, using such sequences; the resonances from the doublet may overlap with each other, or with the zero-frequency glitch. This limitation has prevented the widespread use of 1H chemical shift anisotropy (CSA) for the measurement of dynamics, particularly for CH protons which typically have CSAs of only a few ppm when immobile. Here, we introduce a simple modification to the traditional 1H CSA and proton-detected local field pulse sequences that enables the acquisition of a hypercomplex dataset and the removal of the uncorrelated magnetization that results in the zero-frequency glitch. These new sequences then yield a frequency shift in the indirect dimension, rather than a splitting, which is easily identifiable even in cases of weak interactions.
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Zhang R, Hong YL, Ravula T, Nishiyama Y, Ramamoorthy A. High-resolution proton-detected MAS experiments on self-assembled diphenylalanine nanotubes enabled by fast MAS and high magnetic field. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 313:106717. [PMID: 32240957 DOI: 10.1016/j.jmr.2020.106717] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/10/2020] [Accepted: 03/11/2020] [Indexed: 06/11/2023]
Abstract
The advent of ultrahigh magnetic field and fast magic-angle-spinning (MAS) probe technology has led to dramatically enhanced spectral resolution and sensitivity in solid-state NMR spectroscopy. In particular, proton-based multidimensional solid-state NMR techniques have become feasible to investigate the structure and dynamics at atomic resolution, due to the increased chemical shift span and spectral resolution. Herein, the benefits of faster MAS and higher magnetic field are demonstrated on a self-assembled diphenylalanine (Phe-Phe) nanomaterial. Proton-detected 2D 1H/1H single-quantum/single-quantum (SQ/SQ) correlation, double-quantum/single-quantum (DQ/SQ) correlation, and 1H chemical shift anisotropy/chemical shift (CSA/CS) correlation spectra obtained at two different spinning speeds (60 and 100 kHz) and two different magnetic fields (600 and 900 MHz) are reported. The dramatic enhancement of proton spectral resolution achieved with the use of a 900 MHz magnetic field and 100 kHz MAS is remarkable and enabled the measurement of proton CSA tensors, which will be useful to better understand the self-assembled structures of Phe-Phe nanotubes. We also show through numerical simulations that the unaveraged proton-proton dipolar couplings can result in broadening of CSA lines, leading to inaccurate determination of CSA tensors of protons. Thus, our results clearly show the insufficiency of a 600 MHz magnetic field to resolve 1H spectra lines and the inability of a moderate spinning speed of 60 kHz to completely suppress 1H-1H dipolar couplings, which further justify the pursuit of ultrahigh magnetic field beyond 1 GHz and ultrafast MAS beyond 100 kHz.
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Affiliation(s)
- Rongchun Zhang
- Biophysics and Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109-1055, USA.
| | - You-Lee Hong
- Nano-Crystallography Unit, RIKEN-JEOL Collaboration Center, Tsurumi, Yokohama, Kanagawa 230-0045, Japan; Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Institute for Advanced Study, and AIST-Kyoto University Chemical Energy Material Open Innovation Laboratory (ChEM-OIL), Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Thirupathi Ravula
- Biophysics and Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Yusuke Nishiyama
- Nano-Crystallography Unit, RIKEN-JEOL Collaboration Center, Tsurumi, Yokohama, Kanagawa 230-0045, Japan; NMR Science and Development Division, RIKEN SPring-8 Center, Tsurumi, Yokohama, Kanagawa 230-0045, Japan; JEOL RESONANCE Inc., Musashino, Akishima, Tokyo 196-8558, Japan
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, Biomedical Engineering, Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109-1055, USA.
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Rossi F, Duong NT, Pandey MK, Chierotti MR, Gobetto R, Nishiyama Y. Determination of the 15 N chemical shift anisotropy in natural abundance samples by proton-detected 3D solid-state NMR under ultrafast MAS of 70 kHz. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2019; 57:294-303. [PMID: 30684385 DOI: 10.1002/mrc.4841] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 01/17/2019] [Accepted: 01/19/2019] [Indexed: 06/09/2023]
Abstract
Chemical shift anisotropy (CSA) is a sensitive probe of electronic environment at a nucleus, and thus, it offers deeper insights into detailed structural and dynamic properties of different systems, for example, chemical, biological, and materials. Over the years, massive efforts have been made to develop recoupling methods that reintroduce CSA interaction under magic angle spinning (MAS) conditions. Most of them require slow or moderate MAS (≤20 kHz) and isotopically enriched samples. On the other hand, to the best of the authors' knowledge, no 13 C or 15 N CSA recoupling schemes at ultrafast MAS (≥60 kHz) suitable for cost-effective natural abundant samples have been developed. We present here a proton-detected 3D 15 N CS/15 N CSA/1 H CS correlation experiment which employs 1 H indirect detection for sensitivity enhancement and a γ-encoded RNnν -symmetry-based CSA recoupling scheme. In particular, two different symmetries, that is, R837 and R1049 , are first tested, in a 2D 15 N CSA/1 H CS version, on [U-15 N]-L-histidine·HCl·H2 O as a model sample under 70 kHz MAS. Then the 3D experiment is applied on glycyl-L-alanine at natural abundance, resulting in site-resolved 15 N CSA lineshapes from which CSA parameters are retrieved by SIMPSON numerical fittings. We demonstrate that this 3D R-symmetry-based pulse sequence is highly robust with respect to wide-range offset mismatches and weakly dependent to rf inhomogeneity within mis-sets of ±10% from the theoretical value.
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Affiliation(s)
- Federica Rossi
- Department of Chemistry and NIS Centre, University of Torino, V. P. Giuria 7, Torino, Italy
| | | | - Manoj Kumar Pandey
- Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab, India
| | - Michele R Chierotti
- Department of Chemistry and NIS Centre, University of Torino, V. P. Giuria 7, Torino, Italy
| | - Roberto Gobetto
- Department of Chemistry and NIS Centre, University of Torino, V. P. Giuria 7, Torino, Italy
| | - Yusuke Nishiyama
- RIKEN-JEOL Collaboration Center, Yokohama, Kanagawa, Japan
- NMR Science and Development Division, RIKEN SPring-8 Center, Yokohama, Kanagawa, Japan
- JEOL RESONANCE Inc., Musashino, Akishima, Tokyo, Japan
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11
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Czernek J, Brus J. Exploring Accuracy Limits of Predictions of the 1H NMR Chemical Shielding Anisotropy in the Solid State. Molecules 2019; 24:E1731. [PMID: 31058873 PMCID: PMC6539467 DOI: 10.3390/molecules24091731] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 04/25/2019] [Accepted: 04/30/2019] [Indexed: 11/16/2022] Open
Abstract
The 1H chemical shielding anisotropy (CSA) is an NMR parameter that is exquisitely sensitive to the local environment of protons in crystalline systems, but it is difficult to obtain it experimentally due to the need to concomitantly suppress other anisotropic interactions in the solid-state NMR (SSNMR) pulse sequences. The SSNMR measurements of the 1H CSA are particularly challenging if the fast magic-angle-spinning (MAS) is applied. It is thus important to confront the results of both the single-crystal (SC) and fast-MAS experiments with their theoretical counterparts. Here the plane-waves (PW) DFT calculations have been carried out using two functionals in order to precisely characterize the structures and the 1H NMR chemical shielding tensors (CSTs) of the solid forms of maleic, malonic, and citric acids, and of L-histidine hydrochloride monohydrate. The level of agreement between the PW DFT and either SC or fast-MAS SSNMR 1H CSA data has been critically compared. It has been found that for the eigenvalues of the 1H CSTs provided by the fast-MAS measurements, an accuracy limit of current PW DFT predictions is about two ppm in terms of the standard deviation of the linear regression model, and sources of this error have been thoroughly discussed.
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Affiliation(s)
- Jiří Czernek
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovsky Square 2, 16206 Prague, Czech Republic.
| | - Jiří Brus
- Institute of Macromolecular Chemistry, Czech Academy of Sciences, Heyrovsky Square 2, 16206 Prague, Czech Republic.
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Pandey MK, Damron JT, Ramamoorthy A, Nishiyama Y. Proton-detected 3D 1H anisotropic/ 14N/ 1H isotropic chemical shifts correlation NMR under fast magic angle spinning on solid samples without isotopic enrichment. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019; 97:40-45. [PMID: 30623800 DOI: 10.1016/j.ssnmr.2018.12.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 12/25/2018] [Accepted: 12/26/2018] [Indexed: 06/09/2023]
Abstract
The chemical shift anisotropy (CSA) interaction of a nucleus is an important indicator of the local electronic environment particularly for the contributions arising from hydrogen (H)-bonding, electrostatic and π-π interactions. CSAs of protons bonded to nitrogen atoms are of significant interest due to their common role as H-bonding partners in many chemical, pharmaceutical and biological systems. Although very fast (∼100 kHz) magic angle sample spinning (MAS) experiments have enabled the measurement of proton CSAs directly from solids, due to a narrow chemical shift (CS) distribution, overlapping NH proton resonances are common and necessitate the introduction of an additional frequency dimension to the regular 2D 1H CSA/1H CS correlation method to achieve sufficient resolution. While this can be accomplished by using the isotropic shift frequency of 14N or 15N nuclei, the use of the naturally-abundant 14N nucleus avoids 15N isotopic labeling and therefore would be useful for a variety of solids. To this end, we propose a proton-detected 3D 1H CSA/14N/1H CS correlation method under fast MAS (90 kHz) to determine the CSA tensors of NH protons in samples without isotopic enrichment. Our experimental results demonstrate that the proposed 3D NMR experiment is capable of resolving the overlapping 1H resonances of amide (NH) groups through the 14N isotropic shift frequency dimension and enables the accurate measurement of site-specific 1H CSAs directly from powder samples under fast MAS conditions. In addition to the 3D 1H CSA/14N/1H CS experiment, an approach employing 14N-edited 2D 1H CSA/1H CS experiment is also demonstrated as an additional means to address spectral overlap of NH resonances with aliphatic and other proton resonances in solids.
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Affiliation(s)
- Manoj Kumar Pandey
- Indian Institute of Technology Ropar, Nangal Road, Rupnagar, 140001, Punjab, India.
| | - Joshua T Damron
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI, 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI, 48109-1055, USA; Biophysics Program, University of Michigan, 930 N. University Ave., Ann Arbor, MI, 48109, USA
| | - Yusuke Nishiyama
- RIKEN-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa, 230-0045, Japan; JEOL RESONANCE Inc., Musashino, Akishima, Tokyo, 196-8558, Japan.
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13
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Veinberg SL, Lindquist AW, Jaroszewicz MJ, Schurko RW. Practical considerations for the acquisition of ultra-wideline 14N NMR spectra. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2017; 84:45-58. [PMID: 28130009 DOI: 10.1016/j.ssnmr.2016.12.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 12/20/2016] [Accepted: 12/20/2016] [Indexed: 06/06/2023]
Abstract
Several considerations for the acquisition, processing, and analysis of high quality ultra-wideline (UW) 14N solid-state NMR (SSNMR) powder patterns under static conditions are discussed. It is shown that the 14N quadrupolar parameters may be determined accurately using the frequencies of only two discontinuities in 14N NMR powder patterns that are dominated by the first-order quadrupolar interaction, thereby eliminating the need for the acquisition of the entire pattern and concomitantly reducing experimental time. A framework for utilizing the WURST-CPMG pulse sequence to improve the efficiency of UW 14N SSNMR experiments is explored in two parts: (i) a systematic investigation of the design and parameterization of the WURST pulse is presented, and (ii) the development of the practical aspects of CPMG refocusing for the acquisition of UW 14N SSNMR powder patterns is discussed, with a focus on maximizing both signal-to-noise and resolution, and minimizing spectral distortions. Finally, a strategy is demonstrated that allows for the measurement of the 14N quadrupolar parameters for any nitrogen moiety whose quadrupolar coupling constant falls within the range 0.8≤|CQ|≤1.5MHz, by acquiring only two 14N NMR sub-spectra at strategically located transmitter frequencies; these results are compared to full powder patterns which are acquired using frequency-stepped methods. The methodologies and practical considerations outlined herein are not only useful for the rapid acquisition of UW 14N NMR spectra, but may also be modified and applied for UW NMR of a plethora of quadrupolar and spin-1/2 nuclides.
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Affiliation(s)
- Stanislav L Veinberg
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B 3P4
| | - Austin W Lindquist
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B 3P4
| | - Michael J Jaroszewicz
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B 3P4
| | - Robert W Schurko
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B 3P4.
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14
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Zhang R, Duong NT, Nishiyama Y, Ramamoorthy A. 3D Double-Quantum/Double-Quantum Exchange Spectroscopy of Protons under 100 kHz Magic Angle Spinning. J Phys Chem B 2017; 121:5944-5952. [DOI: 10.1021/acs.jpcb.7b03480] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Rongchun Zhang
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Nghia Tuan Duong
- RIKEN
CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Yusuke Nishiyama
- RIKEN
CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
- JEOL Resonance Inc., Musashino, Akishima, Tokyo 196-8558, Japan
| | - Ayyalusamy Ramamoorthy
- Biophysics
and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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15
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Nishiyama Y. Fast magic-angle sample spinning solid-state NMR at 60-100kHz for natural abundance samples. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2016; 78:24-36. [PMID: 27400153 DOI: 10.1016/j.ssnmr.2016.06.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 06/07/2016] [Accepted: 06/08/2016] [Indexed: 06/06/2023]
Abstract
In spite of tremendous progress made in pulse sequence designs and sophisticated hardware developments, methods to improve sensitivity and resolution in solid-state NMR (ssNMR) are still emerging. The rate at which sample is spun at magic angle determines the extent to which sensitivity and resolution of NMR spectra are improved. To this end, the prime objective of this article is to give a comprehensive theoretical and experimental framework of fast magic angle spinning (MAS) technique. The engineering design of fast MAS rotors based on spinning rate, sample volume, and sensitivity is presented in detail. Besides, the benefits of fast MAS citing the recent progress in methodology, especially for natural abundance samples are also highlighted. The effect of the MAS rate on (1)H resolution, which is a key to the success of the (1)H inverse detection methods, is described by a simple mathematical factor named as the homogeneity factor k. A comparison between various (1)H inverse detection methods is also presented. Moreover, methods to reduce the number of spinning sidebands (SSBs) for the systems with huge anisotropies in combination with (1)H inverse detection at fast MAS are discussed.
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Affiliation(s)
- Yusuke Nishiyama
- RIKEN CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan; JEOL RESONANCE Inc., Musashino, Akishima, Tokyo 186-8558, Japan.
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16
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Pandey MK, Yarava JR, Zhang R, Ramamoorthy A, Nishiyama Y. Proton-detected 3D (15)N/(1)H/(1)H isotropic/anisotropic/isotropic chemical shift correlation solid-state NMR at 70kHz MAS. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2016; 76-77:1-6. [PMID: 27017575 PMCID: PMC4903906 DOI: 10.1016/j.ssnmr.2016.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/18/2016] [Accepted: 03/01/2016] [Indexed: 05/15/2023]
Abstract
Chemical shift anisotropy (CSA) tensors offer a wealth of information for structural and dynamics studies of a variety of chemical and biological systems. In particular, CSA of amide protons can provide piercing insights into hydrogen-bonding interactions that vary with the backbone conformation of a protein and dynamics. However, the narrow span of amide proton resonances makes it very difficult to measure (1)H CSAs of proteins even by using the recently proposed 2D (1)H/(1)H anisotropic/isotropic chemical shift (CSA/CS) correlation technique. Such difficulties due to overlapping proton resonances can in general be overcome by utilizing the broad span of isotropic chemical shifts of low-gamma nuclei like (15)N. In this context, we demonstrate a proton-detected 3D (15)N/(1)H/(1)H CS/CSA/CS correlation experiment at fast MAS frequency (70kHz) to measure (1)H CSA values of unresolved amide protons of N-acetyl-(15)N-l-valyl-(15)N-l-leucine (NAVL).
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Affiliation(s)
- Manoj Kumar Pandey
- RIKEN CLST-JEOL Collaboration Center, Yokohama, Kanagawa 230-0045, Japan
| | | | - Rongchun Zhang
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Yusuke Nishiyama
- RIKEN CLST-JEOL Collaboration Center, Yokohama, Kanagawa 230-0045, Japan; JEOL RESONANCE Inc., Musashino, Akishima, Tokyo 196-8558, Japan.
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17
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Zhang R, Ramamoorthy A. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS. J Chem Phys 2016; 144:034202. [PMID: 26801026 PMCID: PMC4723396 DOI: 10.1063/1.4940029] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 01/04/2016] [Indexed: 12/13/2022] Open
Abstract
Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D (1)H/(13)C/(1)H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t1 and t3 periods, respectively. In addition to through-space and through-bond (13)C/(1)H and (13)C/(13)C chemical shift correlations, the 3D (1)H/(13)C/(1)H experiment also provides a COSY-type (1)H/(1)H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices ((1)H/(1)H chemical shift correlation spectrum) at different (13)C chemical shift frequencies from the 3D (1)H/(13)C/(1)H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D (1)H/(13)C/(1)H experiment would be useful to study the structure and dynamics of a variety of chemical and biological solids.
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Affiliation(s)
- Rongchun Zhang
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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18
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Pandey MK, Nishiyama Y. Determination of NH proton chemical shift anisotropy with (14)N-(1)H heteronuclear decoupling using ultrafast magic angle spinning solid-state NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 261:133-40. [PMID: 26580062 DOI: 10.1016/j.jmr.2015.10.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 10/21/2015] [Accepted: 10/25/2015] [Indexed: 05/27/2023]
Abstract
The extraction of chemical shift anisotropy (CSA) tensors of protons either directly bonded to (14)N nuclei (I=1) or lying in their vicinity using rotor-synchronous recoupling pulse sequence is always fraught with difficulty due to simultaneous recoupling of (14)N-(1)H heteronuclear dipolar couplings and the lack of methods to efficiently decouple these interactions. This difficulty mainly arises from the presence of large (14)N quadrupolar interactions in comparison to the rf field that can practically be achieved. In the present work it is demonstrated that the application of on-resonance (14)N-(1)H decoupling with rf field strength ∼30 times weaker than the (14)N quadrupolar coupling during (1)H CSA recoupling under ultrafast MAS (90kHz) results in CSA lineshapes that are free from any distortions from recoupled (14)N-(1)H interactions. With the use of extensive numerical simulations we have shown the applicability of our proposed method on a naturally abundant l-Histidine HCl·H2O sample.
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Affiliation(s)
- Manoj Kumar Pandey
- RIKEN CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Yusuke Nishiyama
- RIKEN CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan; JEOL RESONANCE Inc., Musashino, Akishima, Tokyo 196-8558, Japan.
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19
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Pandey MK, Zhang R, Hashi K, Ohki S, Nishijima G, Matsumoto S, Noguchi T, Deguchi K, Goto A, Shimizu T, Maeda H, Takahashi M, Yanagisawa Y, Yamazaki T, Iguchi S, Tanaka R, Nemoto T, Miyamoto T, Suematsu H, Saito K, Miki T, Ramamoorthy A, Nishiyama Y. 1020MHz single-channel proton fast magic angle spinning solid-state NMR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2015; 261:1-5. [PMID: 26524647 PMCID: PMC4688097 DOI: 10.1016/j.jmr.2015.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 10/09/2015] [Accepted: 10/11/2015] [Indexed: 05/05/2023]
Abstract
This study reports a first successful demonstration of a single channel proton 3D and 2D high-throughput ultrafast magic angle spinning (MAS) solid-state NMR techniques in an ultra-high magnetic field (1020MHz) NMR spectrometer comprised of HTS/LTS magnet. High spectral resolution is well demonstrated.
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Affiliation(s)
- Manoj Kumar Pandey
- RIKEN CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Rongchun Zhang
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Kenjiro Hashi
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Shinobu Ohki
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Gen Nishijima
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Shinji Matsumoto
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Takashi Noguchi
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Kenzo Deguchi
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Atsushi Goto
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Tadashi Shimizu
- National Institute for Materials Science, Sakura, Tsukuba, Ibaraki 305-0003, Japan
| | - Hideaki Maeda
- Center for Life Science Technologies, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Masato Takahashi
- Center for Life Science Technologies, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | | | - Toshio Yamazaki
- Center for Life Science Technologies, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Seiya Iguchi
- Center for Life Science Technologies, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Ryoji Tanaka
- JEOL RESONANCE Inc., Akishima, Tokyo 196-8558, Japan
| | | | | | | | | | | | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, MI 48109-1055, USA.
| | - Yusuke Nishiyama
- RIKEN CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan; JEOL RESONANCE Inc., Akishima, Tokyo 196-8558, Japan.
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20
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Zhang R, Mroue KH, Ramamoorthy A. Proton chemical shift tensors determined by 3D ultrafast MAS double-quantum NMR spectroscopy. J Chem Phys 2015; 143:144201. [PMID: 26472372 PMCID: PMC4608963 DOI: 10.1063/1.4933114] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 10/01/2015] [Indexed: 12/18/2022] Open
Abstract
Proton NMR spectroscopy in the solid state has recently attracted much attention owing to the significant enhancement in spectral resolution afforded by the remarkable advances in ultrafast magic angle spinning (MAS) capabilities. In particular, proton chemical shift anisotropy (CSA) has become an important tool for obtaining specific insights into inter/intra-molecular hydrogen bonding. However, even at the highest currently feasible spinning frequencies (110-120 kHz), (1)H MAS NMR spectra of rigid solids still suffer from poor resolution and severe peak overlap caused by the strong (1)H-(1)H homonuclear dipolar couplings and narrow (1)H chemical shift (CS) ranges, which render it difficult to determine the CSA of specific proton sites in the standard CSA/single-quantum (SQ) chemical shift correlation experiment. Herein, we propose a three-dimensional (3D) (1)H double-quantum (DQ) chemical shift/CSA/SQ chemical shift correlation experiment to extract the CS tensors of proton sites whose signals are not well resolved along the single-quantum chemical shift dimension. As extracted from the 3D spectrum, the F1/F3 (DQ/SQ) projection provides valuable information about (1)H-(1)H proximities, which might also reveal the hydrogen-bonding connectivities. In addition, the F2/F3 (CSA/SQ) correlation spectrum, which is similar to the regular 2D CSA/SQ correlation experiment, yields chemical shift anisotropic line shapes at different isotropic chemical shifts. More importantly, since the F2/F1 (CSA/DQ) spectrum correlates the CSA with the DQ signal induced by two neighboring proton sites, the CSA spectrum sliced at a specific DQ chemical shift position contains the CSA information of two neighboring spins indicated by the DQ chemical shift. If these two spins have different CS tensors, both tensors can be extracted by numerical fitting. We believe that this robust and elegant single-channel proton-based 3D experiment provides useful atomistic-level structural and dynamical information for a variety of solid systems that possess high proton density.
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Affiliation(s)
- Rongchun Zhang
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Kamal H Mroue
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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