Pub Date : 2023-02-01DOI: 10.1016/j.ssnmr.2022.101849
Leo Svenningsson , Leonard J. Mueller
TensorView for MATLAB is a GUI-based visualization tool for depicting second-rank Cartesian tensors as surfaces on three-dimensional molecular models. Both ellipsoid and ovaloid tensor display formats are supported, and the software allows for easy conversion of Euler angles from common rotation schemes (active, passive, ZXZ, and ZYZ conventions) with visual feedback. In addition, the software displays all four orientation-equivalent Euler angle solutions for the placement of a single tensor in the molecular frame and can report relative orientations of two tensors with all 16 orientation-equivalent Euler angle sets that relate them. The salient relations are derived and illustrated through several examples. TensorView for MATLAB expands and complements the earlier implementation of TensorView within the Mathematica programming environment and can be run without a MATLAB license. TensorView for MATLAB is available through github at https://github.com/LeoSvenningsson/TensorViewforMatlab, and can also be accessed directly via the NMRbox resource.
TensorView for MATLAB是一个基于GUI的可视化工具,用于将二阶笛卡尔张量描述为三维分子模型上的曲面。支持椭球和椭圆张量显示格式,该软件允许通过视觉反馈轻松转换常见旋转方案(主动、被动、ZXZ和ZYZ约定)的欧拉角。此外,该软件显示了在分子框架中放置单个张量的所有四个方向等效欧拉角解,并可以报告两个张量的相对方向以及与它们相关的所有16个方向等效的欧拉角集。通过几个例子推导和说明了显著的关系。TensorView for MATLAB扩展并补充了早期在Mathematica编程环境中实现的TensorView,并且可以在没有MATLAB许可证的情况下运行。用于MATLAB的TensorView可通过github获得,网址为https://github.com/LeoSvenningsson/TensorViewforMatlab,也可以通过NMRbox资源直接访问。
{"title":"TensorView for MATLAB: Visualizing tensors with Euler angle decoding","authors":"Leo Svenningsson , Leonard J. Mueller","doi":"10.1016/j.ssnmr.2022.101849","DOIUrl":"10.1016/j.ssnmr.2022.101849","url":null,"abstract":"<div><p>TensorView for MATLAB is a GUI-based visualization tool for depicting second-rank Cartesian tensors as surfaces on three-dimensional molecular models. Both ellipsoid and ovaloid tensor display formats are supported, and the software allows for easy conversion of Euler angles from common rotation schemes (active, passive, ZXZ, and ZYZ conventions) with visual feedback. In addition, the software displays all four orientation-equivalent Euler angle solutions for the placement of a single tensor in the molecular frame and can report relative orientations of two tensors with all 16 orientation-equivalent Euler angle sets that relate them. The salient relations are derived and illustrated through several examples. TensorView for MATLAB expands and complements the earlier implementation of TensorView within the Mathematica programming environment and can be run without a MATLAB license. TensorView for MATLAB is available through github at <span>https://github.com/LeoSvenningsson/TensorViewforMatlab</span><svg><path></path></svg>, and can also be accessed directly via the NMRbox resource.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10238149/pdf/nihms-1903353.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9915498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-01DOI: 10.1016/j.ssnmr.2022.101850
Adam N. Smith , Rania Harrabi , Thomas Halbritter , Daniel Lee , Fabien Aussenac , Patrick C.A. van der Wel , Sabine Hediger , Snorri Th. Sigurdsson , Gaël De Paëpe
We show that multidimensional solid-state NMR 13C–13C correlation spectra of biomolecular assemblies and microcrystalline organic molecules can be acquired at natural isotopic abundance with only milligram quantities of sample. These experiments combine fast Magic Angle Spinning of the sample, low-power dipolar recoupling, and dynamic nuclear polarization performed with AsymPol biradicals, a recently introduced family of polarizing agents. Such experiments are essential for structural characterization as they provide short- and long-range distance information. This approach is demonstrated on diverse sample types, including polyglutamine fibrils implicated in Huntington's disease and microcrystalline ampicillin, a small antibiotic molecule.
{"title":"Fast magic angle spinning for the characterization of milligram quantities of organic and biological solids at natural isotopic abundance by 13C–13C correlation DNP-enhanced NMR","authors":"Adam N. Smith , Rania Harrabi , Thomas Halbritter , Daniel Lee , Fabien Aussenac , Patrick C.A. van der Wel , Sabine Hediger , Snorri Th. Sigurdsson , Gaël De Paëpe","doi":"10.1016/j.ssnmr.2022.101850","DOIUrl":"https://doi.org/10.1016/j.ssnmr.2022.101850","url":null,"abstract":"<div><p>We show that multidimensional solid-state NMR <sup>13</sup>C–<sup>13</sup><span><span><span>C correlation spectra of biomolecular assemblies and microcrystalline organic molecules can be acquired at natural isotopic abundance with only milligram quantities of sample. These experiments combine fast </span>Magic Angle Spinning of the sample, low-power </span>dipolar recoupling<span><span>, and dynamic nuclear polarization performed with AsymPol biradicals, a recently introduced family of polarizing agents. Such experiments are essential for structural characterization as they provide short- and long-range distance information. This approach is demonstrated on diverse sample types, including polyglutamine fibrils implicated in Huntington's disease and microcrystalline </span>ampicillin, a small antibiotic molecule.</span></span></p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49815672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-01DOI: 10.1016/j.ssnmr.2022.101848
Darren H. Brouwer, Janelle G. Mikolajewski
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.
{"title":"A combined solid-state NMR and quantum chemical calculation study of hydrogen bonding in two forms of α-d-glucose","authors":"Darren H. Brouwer, Janelle G. Mikolajewski","doi":"10.1016/j.ssnmr.2022.101848","DOIUrl":"10.1016/j.ssnmr.2022.101848","url":null,"abstract":"<div><p><span>Hydrogen bonding plays an important role in the structure and function of a wide range of materials. Solid-state </span><sup>1</sup><span>H 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 </span><sup>1</sup><span>H solid-state NMR data on O–H - - O hydrogen bonding in solid carboxylic acids, there has been no systematic </span><sup>1</sup><span>H solid-state NMR studies of hydroxyl<span><span> groups in carbohydrates (and hydroxyl groups in general). With a view to studying the hydrogen bonding in more complex materials such as </span>cellulose polymorphs, we carried out a detailed solid-state </span></span><sup>1</sup>H NMR investigation of the model compounds α-<span>d</span>-glucose and α-<span>d</span><span>-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 (H</span><sub>2</sub>O) <sup>1</sup>H chemical shifts in both forms of α-<span>d</span>-glucose. Plane-wave DFT calculations were employed to improve the hydrogen atom positions for α-<span>d</span>-glucose monohydrate and to calculate <sup>1</sup>H chemical shifts, providing additional support for the experimentally determined peak assignments. Finally, the relationship between the hydroxyl <sup>1</sup>H chemical shifts and their hydrogen bonding geometry was investigated and compared to the well-established relationship for carboxylic acid protons.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10626686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-01DOI: 10.1016/j.ssnmr.2022.101821
Sadasivan V. Sajith , Sundaresan Jayanthi , Adonis Lupulescu
We present a theoretical and numerical description of the spin dynamics associated with TRAPDOR-HMQC (T-HMQC) experiment for a 1H (I) – 35Cl (S) spin system under fast magic angle spinning (MAS). Towards this an exact effective Hamiltonian describing the system is numerically evaluated with matrix logarithm approach. The different magnitudes of the heteronuclear and pure S terms in the effective Hamiltonian allow us to suggest a truncation approximation, which is shown to be in excellent agreement with the exact time evolution. Limitations of this approximation, especially at the rotary resonance condition, are discussed. The truncated effective Hamiltonian is further employed to monitor the buildup of various coherences during TRAPDOR irradiation. We observe and explain a functional resemblance between the magnitude of different terms in the truncated effective Hamiltonian and the amplitudes of various coherences during TRAPDOR irradiation, as function of crystallite orientation. Subsequently, the dependence of the sign (phase) of the T-HMQC signal on the coherence type generated is investigated numerically and analytically. We examine the continuous creation and evolution of various coherences at arbitrary times, i.e., at and between avoided level crossings. Behavior between consecutive crossings is described analytically and reveals ‘quadrature’ evolution of pairs of coherences and coherence interconversions. The adiabatic, sudden, and intermediate regimes for T-HMQC experiments are discussed within the approach established by A. J. Vega. Equations as well as numerical simulations suggest the existence of a driving coherence which builds up between consecutive crossings and then gets distributed at crossings among other coherences. In the intermediate regime, redistribution of the driving coherence to other coherences is almost uniform such that coherences involving S-spin double-quantum terms may be efficiently produced.
{"title":"Effective Hamiltonian and spin dynamics in fast MAS TRAPDOR-HMQC experiments involving spin-3/2 quadrupolar nuclei","authors":"Sadasivan V. Sajith , Sundaresan Jayanthi , Adonis Lupulescu","doi":"10.1016/j.ssnmr.2022.101821","DOIUrl":"10.1016/j.ssnmr.2022.101821","url":null,"abstract":"<div><p>We present a theoretical and numerical description of the spin dynamics associated with TRAPDOR-HMQC (T-HMQC) experiment for a <sup>1</sup>H (<em>I</em>) – <sup>35</sup>Cl (<em>S</em><span>) spin system under fast magic angle spinning (MAS). Towards this an exact effective Hamiltonian describing the system is numerically evaluated with </span><em>matrix logarithm</em> approach. The different magnitudes of the <em>heteronuclear</em> and <span><em>pure</em><em> S</em></span><span> terms in the effective Hamiltonian allow us to suggest a truncation approximation, which is shown to be in excellent agreement with the exact time evolution. Limitations of this approximation, especially at the rotary resonance condition, are discussed. The truncated effective Hamiltonian is further employed to monitor the buildup of various coherences during TRAPDOR<span> irradiation. We observe and explain a functional resemblance between the magnitude of different terms in the truncated effective Hamiltonian and the amplitudes of various coherences during TRAPDOR irradiation, as function of crystallite orientation. Subsequently, the dependence of the sign (phase) of the T-HMQC signal on the coherence type generated is investigated numerically and analytically. We examine the continuous creation and evolution of various coherences at arbitrary times, i.e., at and between avoided level crossings. Behavior between consecutive crossings is described analytically and reveals ‘quadrature’ evolution of pairs of coherences and </span></span><em>coherence interconversions</em>. The adiabatic, sudden, and intermediate regimes for T-HMQC experiments are discussed within the approach established by A. J. Vega. Equations as well as numerical simulations suggest the existence of a driving coherence which builds up between consecutive crossings and then gets distributed at crossings among other coherences. In the intermediate regime, redistribution of the driving coherence to other coherences is almost uniform such that coherences involving <em>S</em>-spin double-quantum terms may be efficiently produced.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40395211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-01DOI: 10.1016/j.ssnmr.2022.101837
Sean T. Holmes , Cameron S. Vojvodin , Natan Veinberg , Emilia M. Iacobelli , David A. Hirsh , Robert W. Schurko
This study uses 35Cl and 2H solid-state NMR (SSNMR) spectroscopy and dispersion-corrected plane-wave density functional theory (DFT) calculations to characterize the molecular-level structures and dynamics of hydrates of active pharmaceutical ingredients (APIs). We use 35Cl SSNMR to measure the EFG tensors of the chloride ions to characterize hydrated forms of hydrochloride salts of APIs, along with two corresponding anhydrous forms. DFT calculations are used to refine the crystal structures of the APIs and determine relationships between the 35Cl EFG tensors and the spatial arrangements of proximate hydrogen bonds, which are particularly influenced by interactions with water molecules. We find that the relationship between 35Cl EFG tensors and local hydrogen bonding geometries is complex, but meaningful structure/property relationships can be garnered through use of DFT calculations. Specifically, for every case in which such a comparison could be made, we find that the hydrate has a smaller magnitude of CQ than the corresponding anhydrous form, indicating a chloride ion environment with a ground-state electron density of higher spherical symmetry in the former. Finally, variable-temperature 35Cl and 2H SSNMR experiments on a deuterium-exchanged sample of the API cimetidine hydrochloride monohydrate are used to monitor temperature-dependent influences on the spectra that may arise from motional influences on the 35Cl and 2H EFG tensors. From the 2H SSNMR spectra, we determine that the motions of water molecules are characterized by jump-like motions about their C2 rotational axes that occur on timescales that are unlikely to influence the 35Cl central-transition (+1/2 ↔︎ −1/2) powder patterns (this is confirmed by 35Cl SSNMR). Together, these methods show great promise for the future study of APIs in their bulk and dosage forms, especially variable hydrates in which crystallographic water content varies with external conditions such as humidity.
{"title":"Hydrates of active pharmaceutical ingredients: A 35Cl and 2H solid-state NMR and DFT study","authors":"Sean T. Holmes , Cameron S. Vojvodin , Natan Veinberg , Emilia M. Iacobelli , David A. Hirsh , Robert W. Schurko","doi":"10.1016/j.ssnmr.2022.101837","DOIUrl":"https://doi.org/10.1016/j.ssnmr.2022.101837","url":null,"abstract":"<div><p>This study uses <sup>35</sup>Cl and <sup>2</sup>H solid-state NMR (SSNMR) spectroscopy and dispersion-corrected plane-wave density functional theory (DFT) calculations to characterize the molecular-level structures and dynamics of hydrates of active pharmaceutical ingredients (APIs). We use <sup>35</sup><span><span>Cl SSNMR to measure the EFG tensors of the </span>chloride ions to characterize hydrated forms of hydrochloride salts of APIs, along with two corresponding anhydrous forms. DFT calculations are used to refine the crystal structures of the APIs and determine relationships between the </span><sup>35</sup><span>Cl EFG tensors and the spatial arrangements of proximate hydrogen bonds, which are particularly influenced by interactions with water molecules. We find that the relationship between </span><sup>35</sup>Cl EFG tensors and local hydrogen bonding geometries is complex, but meaningful structure/property relationships can be garnered through use of DFT calculations. Specifically, for every case in which such a comparison could be made, we find that the hydrate has a smaller magnitude of <em>C</em><sub>Q</sub> than the corresponding anhydrous form, indicating a chloride ion environment with a ground-state electron density of higher spherical symmetry in the former. Finally, variable-temperature <sup>35</sup>Cl and <sup>2</sup>H SSNMR experiments on a deuterium-exchanged sample of the API cimetidine hydrochloride monohydrate are used to monitor temperature-dependent influences on the spectra that may arise from motional influences on the <sup>35</sup>Cl and <sup>2</sup>H EFG tensors. From the <sup>2</sup>H SSNMR spectra, we determine that the motions of water molecules are characterized by jump-like motions about their <em>C</em><sub>2</sub> rotational axes that occur on timescales that are unlikely to influence the <sup>35</sup>Cl central-transition (+1/2 ↔︎ −1/2) powder patterns (this is confirmed by <sup>35</sup>Cl SSNMR). Together, these methods show great promise for the future study of APIs in their bulk and dosage forms, especially variable hydrates in which crystallographic water content varies with external conditions such as humidity.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91684899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-01DOI: 10.1016/j.ssnmr.2022.101838
Frédéric Mentink-Vigier , Samuel Eddy , Terry Gullion
NMR is a valuable tool for studying insects. Solid-state NMR has been used to obtain the chemical composition and gain insight into the sclerotization process of exoskeletons. There is typically little difficulty in obtaining sufficient sample quantity for exoskeletons. However, obtaining enough sample of other insect components for solid-state NMR experiments can be problematic while isotopically enriching them is near impossible. This is especially the case for insect wing membranes which is of interest to us. Issues with obtaining sufficient sample are the thickness of wing membranes is on the order of microns, each membrane region is surrounded by veins and occupies a small area, and the membranes are separated from the wing by physical dissection. Accordingly, NMR signal enhancement methods are needed. MAS-DNP has a track record of providing significant signal enhancements for a wide variety of materials. Here we demonstrate that MAS-DNP is useful for providing high quality one-dimensional and two-dimensional solid-state NMR spectra on cicada wing membrane at natural isotopic abundance.
{"title":"MAS-DNP enables NMR studies of insect wings","authors":"Frédéric Mentink-Vigier , Samuel Eddy , Terry Gullion","doi":"10.1016/j.ssnmr.2022.101838","DOIUrl":"10.1016/j.ssnmr.2022.101838","url":null,"abstract":"<div><p><span>NMR is a valuable tool for studying insects. Solid-state NMR has been used to obtain the chemical composition and gain insight into the sclerotization process of exoskeletons. There is typically little difficulty in obtaining sufficient sample quantity for exoskeletons. However, obtaining enough sample of other insect components for solid-state NMR experiments can be problematic while isotopically enriching them is near impossible. This is especially the case for insect wing membranes which is of interest to us. Issues with obtaining sufficient sample are the thickness of wing membranes is on the order of microns, each membrane region is surrounded by veins and occupies a small area, and the membranes are separated from the wing by physical dissection. Accordingly, </span>NMR signal enhancement methods are needed. MAS-DNP has a track record of providing significant signal enhancements for a wide variety of materials. Here we demonstrate that MAS-DNP is useful for providing high quality one-dimensional and two-dimensional solid-state NMR spectra on cicada wing membrane at natural isotopic abundance.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10398228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-01DOI: 10.1016/j.ssnmr.2022.101833
Daphna Shimon , Kelly Cantwell , Linta Joseph , Chandrasekhar Ramanathan
Dynamic nuclear polarization (DNP) is a method of enhancing NMR signals via the transfer of polarization from electron spins to nuclear spins using microwave (MW) irradiation. In most cases, monochromatic continuous-wave (MCW) MW irradiation is used. Recently, several groups have shown that frequency modulation of the MW irradiation can result in an additional increase in DNP enhancement above that obtained with MCW. The effect of frequency modulation on the solid effect (SE) and the cross effect (CE) has previously been studied using the stable organic radical 4-hydroxy TEMPO (TEMPOL) at temperatures under 20 K. Here, in addition to the SE and CE, we discuss the effect of frequency modulation on the Overhauser effect (OE) and the truncated CE (tCE) in the room-temperature 13C-DNP of diamond powders. We recently showed that diamond powders can exhibit multiple DNP mechanisms simultaneously due to the heterogeneity of P1 (substitutional nitrogen) environments within diamond crystallites. We explore how the two parameters that define the frequency modulation: (i) the Modulation frequency, fm (how fast the microwave frequency is varied) and (ii) the Modulation amplitude, Δω (the magnitude of the change in microwave frequency) influence the enhancement obtained via each mechanism. Frequency modulation during DNP not only allows us to improve DNP enhancement, but also gives us a way to control which DNP mechanism is most active. By choosing the appropriate modulation parameters, we can selectively enhance some mechanisms while simultaneously suppressing others.
{"title":"Room temperature DNP of diamond powder using frequency modulation","authors":"Daphna Shimon , Kelly Cantwell , Linta Joseph , Chandrasekhar Ramanathan","doi":"10.1016/j.ssnmr.2022.101833","DOIUrl":"10.1016/j.ssnmr.2022.101833","url":null,"abstract":"<div><p><span><span>Dynamic nuclear polarization (DNP) is a method of enhancing </span>NMR signals<span> via the transfer of polarization from electron spins<span> to nuclear spins using microwave (MW) irradiation. In most cases, monochromatic continuous-wave (MCW) MW irradiation is used. Recently, several groups have shown that frequency modulation of the MW irradiation can result in an additional increase in DNP enhancement above that obtained with MCW. The effect of frequency modulation on the solid effect (SE) and the cross effect (CE) has previously been studied using the stable organic radical 4-hydroxy TEMPO (TEMPOL) at temperatures under 20 K. Here, in addition to the SE and CE, we discuss the effect of frequency modulation on the Overhauser effect (OE) and the truncated CE (tCE) in the room-temperature </span></span></span><sup>13</sup><span>C-DNP of diamond powders. We recently showed that diamond powders can exhibit multiple DNP mechanisms simultaneously due to the heterogeneity of P1 (substitutional nitrogen) environments within diamond crystallites. We explore how the two parameters that define the frequency modulation: (i) the Modulation frequency, f</span><sub><em>m</em></sub> (how fast the microwave frequency is varied) and (ii) the Modulation amplitude, Δω (the magnitude of the change in microwave frequency) influence the enhancement obtained via each mechanism. Frequency modulation during DNP not only allows us to improve DNP enhancement, but also gives us a way to control which DNP mechanism is most active. By choosing the appropriate modulation parameters, we can selectively enhance some mechanisms while simultaneously suppressing others.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33494485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-01DOI: 10.1016/j.ssnmr.2022.101834
Matías Chávez, Matthias Ernst
Interaction frames play an important role in describing and understanding experimental schemes in magnetic resonance. They are often used to eliminate dominating parts of the spin Hamiltonian, e.g., the Zeeman Hamiltonian in the usual (Zeeman) rotating frame, or the radio-frequency-field (rf) Hamiltonian to describe the efficiency of decoupling or recoupling sequences. Going into an interaction frame can also make parts of a time-dependent Hamiltonian time independent like the rf-field Hamiltonian in the usual (Zeeman) rotating frame. Eliminating the dominant term often allows a better understanding of the details of the spin dynamics. Going into an interaction frame can also reduces the energy-level splitting in the Hamiltonian leading to a faster convergence of perturbation expansions, average Hamiltonian, or Floquet theory. Often, there is no obvious choice of the interaction frame to use but some can be more convenient than others. Using the example of frequency-selective dipolar recoupling, we discuss the differences, advantages, and disadvantages of different choices of interaction frames. They always include the complete radio-frequency Hamiltonian but can also contain the chemical shifts of the spins and may or may not contain the effective fields over one cycle of the pulse sequence.
{"title":"Interaction frames in solid-state NMR: A case study for chemical-shift-selective irradiation schemes","authors":"Matías Chávez, Matthias Ernst","doi":"10.1016/j.ssnmr.2022.101834","DOIUrl":"10.1016/j.ssnmr.2022.101834","url":null,"abstract":"<div><p>Interaction frames play an important role in describing and understanding experimental schemes in magnetic resonance. They are often used to eliminate dominating parts of the spin Hamiltonian, e.g., the Zeeman Hamiltonian in the usual (Zeeman) rotating frame, or the radio-frequency-field (rf) Hamiltonian to describe the efficiency of decoupling or recoupling sequences. Going into an interaction frame can also make parts of a time-dependent Hamiltonian time independent like the rf-field Hamiltonian in the usual (Zeeman) rotating frame. Eliminating the dominant term often allows a better understanding of the details of the spin dynamics. Going into an interaction frame can also reduces the energy-level splitting in the Hamiltonian leading to a faster convergence of perturbation expansions, average Hamiltonian, or Floquet theory. Often, there is no obvious choice of the interaction frame to use but some can be more convenient than others. Using the example of frequency-selective dipolar recoupling, we discuss the differences, advantages, and disadvantages of different choices of interaction frames. They always include the complete radio-frequency Hamiltonian but can also contain the chemical shifts of the spins and may or may not contain the effective fields over one cycle of the pulse sequence.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0926204022000637/pdfft?md5=34c8cd6a39dc8784f9deca371b37fc6d&pid=1-s2.0-S0926204022000637-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10341544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-01DOI: 10.1016/j.ssnmr.2022.101820
Tomasz Pawlak , Piotr Paluch , Rafał Dolot , Grzegorz Bujacz , Marek J. Potrzebowski
New salts of teriflunomide TFM (drug approved for Multiple Sclerosis treatment) with inorganic counterions: lithium (TFM_Li), sodium (TFM_Na), potassium (TFM_K), rubidium (TFM_Rb), caesium (TFM_Cs) and ammonium (TFM_NH4) were prepared and investigated employing solid state NMR Spectroscopy, Powder X-ray Diffraction PXRD and Single Crystal X-ray Diffraction (SC XRD). Crystal and molecular structures of three salts: TFM_Na (CCDC: 2173257), TFM_Cs (CCDC: 2165288) and TFM_NH4 (CCDC: 2165281) were determined and deposited. Compared to the native TFM, for all crystalline salt structures, a conformational change of the teriflunomide molecule involving about 180-degree rotation of the end group, forming an intramolecular hydrogen bond N–H⋯O is observed. By applying a complementary multi-technique approach, employing 1D and 2D solid state MAS NMR techniques, single and powder X-ray diffraction measurements, as well as the DFT-based GIPAW calculations of NMR chemical shifts for TFM_Na and TFM_Cs allowed to propose structural features of TFM_Li for which it was not possible to obtain adequate material for single crystal X-Ray measurement.
{"title":"New salts of teriflunomide (TFM) – Single crystal X-ray and solid state NMR investigation","authors":"Tomasz Pawlak , Piotr Paluch , Rafał Dolot , Grzegorz Bujacz , Marek J. Potrzebowski","doi":"10.1016/j.ssnmr.2022.101820","DOIUrl":"10.1016/j.ssnmr.2022.101820","url":null,"abstract":"<div><p>New salts of teriflunomide <strong>TFM</strong> (drug approved for Multiple Sclerosis treatment) with inorganic counterions: lithium (<strong>TFM_Li)</strong>, sodium (<strong>TFM_Na)</strong>, potassium (<strong>TFM_K)</strong>, rubidium (<strong>TFM_Rb)</strong>, caesium (<strong>TFM_Cs)</strong> and ammonium (<strong>TFM_NH</strong><sub><strong>4</strong></sub><strong>)</strong> were prepared and investigated employing solid state NMR Spectroscopy, Powder X-ray Diffraction PXRD and Single Crystal X-ray Diffraction (SC XRD). Crystal and molecular structures of three salts: <strong>TFM_Na</strong> (CCDC: 2173257), <strong>TFM_Cs</strong> (CCDC: 2165288) and <strong>TFM_NH</strong><sub><strong>4</strong></sub> (CCDC: 2165281) were determined and deposited. Compared to the native <strong>TFM</strong>, for all crystalline salt structures, a conformational change of the teriflunomide molecule involving about 180-degree rotation of the end group, forming an intramolecular hydrogen bond N–H⋯O is observed. By applying a complementary multi-technique approach, employing 1D and 2D solid state MAS NMR techniques, single and powder X-ray diffraction measurements, as well as the DFT-based GIPAW calculations of NMR chemical shifts for <strong>TFM_Na</strong> and <strong>TFM_Cs</strong> allowed to propose structural features of <strong>TFM_Li</strong> for which it was not possible to obtain adequate material for single crystal X-Ray measurement.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0926204022000492/pdfft?md5=b5f36b38b63761d08c402a715bb94fef&pid=1-s2.0-S0926204022000492-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10685599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-01DOI: 10.1016/j.ssnmr.2022.101836
Marie Juramy , Paolo Cerreia Vioglio , Fabio Ziarelli , Stéphane Viel , Pierre Thureau , Giulia Mollica
Crystallization is fundamental in many domains, and the investigation of the sequence of solid phases produced as a function of crystallization time is thus key to understand and control crystallization processes. Here, we used a solid-state nuclear magnetic resonance strategy to monitor the crystallization process of glycine, which is a model compound in polymorphism, under the influence of crystallizing additives, such as methanol or sodium chloride. More specifically, our strategy is based on a combination of low-temperatures and dynamic nuclear polarization (DNP) to trap and detect transient crystallizing forms, which may be present only in low quantities. Interestingly, our results show that these additives yield valuable DNP signal enhancements even in the absence of glycerol within the crystallizing solution.
{"title":"Monitoring the influence of additives on the crystallization processes of glycine with dynamic nuclear polarization solid-state NMR","authors":"Marie Juramy , Paolo Cerreia Vioglio , Fabio Ziarelli , Stéphane Viel , Pierre Thureau , Giulia Mollica","doi":"10.1016/j.ssnmr.2022.101836","DOIUrl":"10.1016/j.ssnmr.2022.101836","url":null,"abstract":"<div><p>Crystallization is fundamental in many domains, and the investigation of the sequence of solid phases produced as a function of crystallization time is thus key to understand and control crystallization processes. Here, we used a solid-state nuclear magnetic resonance strategy to monitor the crystallization process of glycine, which is a model compound in polymorphism, under the influence of crystallizing additives, such as methanol or sodium chloride. More specifically, our strategy is based on a combination of low-temperatures and dynamic nuclear polarization (DNP) to trap and detect transient crystallizing forms, which may be present only in low quantities. Interestingly, our results show that these additives yield valuable DNP signal enhancements even in the absence of glycerol within the crystallizing solution.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0926204022000650/pdfft?md5=43ea233eefc61f244122c5bcc4bf4599&pid=1-s2.0-S0926204022000650-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10335669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}