Pub Date : 2025-12-23DOI: 10.1016/j.jmr.2025.108011
Christian M. O'Neil, Lakshmi Bhai, Daniel W. Conroy, Christopher P. Jaroniec
Dynamic nuclear polarization (DNP) enables dramatic sensitivity enhancements of solid-state nuclear magnetic resonance (NMR) spectra for biological systems to be realized via polarization transfer from unpaired electrons of a polarizing agent, typically a nitroxide biradical, to nuclear spins of the system of interest. Here, we systematically investigate the prospect of recording DNP enhanced solid-state NMR spectra of hydrated lattice-like protein assemblies within sample formulations that are free of the commonly employed glycerol-based glassy solvent matrix containing exogenous polarizing agent molecules and instead consist of isotope-enriched protein of interest co-assembled with its dinitroxide-tagged structural analog incorporated as a dopant at low concentration. As a model system we use microcrystals of 13C,15N-labeled immunoglobulin-binding domain of protein G (GB1) doped with different amounts in the ∼1–16 % regime of a GB1 variant, 28R1/32R1, containing nitroxide spin labels at residues 28 and 32. For 28R1/32R1 dopant concentration of 4 %, equivalent to ca. 5 mM polarizing agent in the microcrystals, the DNP signal enhancement for 13C,15N-GB1 was found to be comparable to that obtained for model amino acid 13C,15N-proline in the usual glycerol/D2O/H2O matrix containing 5 mM 28R1/32R1 as the polarizing agent; further sensitivity increases were observed for 28R1/32R1 concentrations on the order of 10 %. Moreover, the spectral resolution for hydrated 13C,15N-GB1 microcrystals doped with 28R1/32R1 at ∼100 K was similar to that for a microcrystal suspension in glycerol/D2O/H2O with AMUPol biradical. This sample formulation approach based on doping with dinitroxide-tagged proteins is expected to be applicable to not only protein microcrystals but also to other lattice-like or filamentous assemblies composed of small to medium-size protein subunits, and further major improvements in sensitivity can be anticipated for this approach with continued development of optimal covalent nitroxide biradical DNP polarizing agent tags.
{"title":"DNP enhanced solid-state NMR of lattice-like microcrystalline protein assemblies facilitated by co-assembly with dinitroxide-tagged proteins","authors":"Christian M. O'Neil, Lakshmi Bhai, Daniel W. Conroy, Christopher P. Jaroniec","doi":"10.1016/j.jmr.2025.108011","DOIUrl":"10.1016/j.jmr.2025.108011","url":null,"abstract":"<div><div>Dynamic nuclear polarization (DNP) enables dramatic sensitivity enhancements of solid-state nuclear magnetic resonance (NMR) spectra for biological systems to be realized via polarization transfer from unpaired electrons of a polarizing agent, typically a nitroxide biradical, to nuclear spins of the system of interest. Here, we systematically investigate the prospect of recording DNP enhanced solid-state NMR spectra of hydrated lattice-like protein assemblies within sample formulations that are free of the commonly employed glycerol-based glassy solvent matrix containing exogenous polarizing agent molecules and instead consist of isotope-enriched protein of interest co-assembled with its dinitroxide-tagged structural analog incorporated as a dopant at low concentration. As a model system we use microcrystals of <sup>13</sup>C,<sup>15</sup>N-labeled immunoglobulin-binding domain of protein G (GB1) doped with different amounts in the ∼1–16 % regime of a GB1 variant, 28R1/32R1, containing nitroxide spin labels at residues 28 and 32. For 28R1/32R1 dopant concentration of 4 %, equivalent to ca. 5 mM polarizing agent in the microcrystals, the DNP signal enhancement for <sup>13</sup>C,<sup>15</sup>N-GB1 was found to be comparable to that obtained for model amino acid <sup>13</sup>C,<sup>15</sup>N-proline in the usual glycerol/D<sub>2</sub>O/H<sub>2</sub>O matrix containing 5 mM 28R1/32R1 as the polarizing agent; further sensitivity increases were observed for 28R1/32R1 concentrations on the order of 10 %. Moreover, the spectral resolution for hydrated <sup>13</sup>C,<sup>15</sup>N-GB1 microcrystals doped with 28R1/32R1 at ∼100 K was similar to that for a microcrystal suspension in glycerol/D<sub>2</sub>O/H<sub>2</sub>O with AMUPol biradical. This sample formulation approach based on doping with dinitroxide-tagged proteins is expected to be applicable to not only protein microcrystals but also to other lattice-like or filamentous assemblies composed of small to medium-size protein subunits, and further major improvements in sensitivity can be anticipated for this approach with continued development of optimal covalent nitroxide biradical DNP polarizing agent tags.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"383 ","pages":"Article 108011"},"PeriodicalIF":1.9,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145835814","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 : 2025-12-18DOI: 10.1016/j.jmr.2025.108010
Anatoliy A. Vereshchagin , Maryam Seif-Eddine , Kaltum Abdiaziz , Maxie M. Roessler , Oleg V. Levin , Jan Behrends
The design and application of a cost-effective, customisable electrochemical cell suitable for in situ X-band (9–10 GHz) Electron Paramagnetic Resonance (EPR) experiments is demonstrated. The cell is optimized for investigating electrochemical parameters of redox-active polymer films at room temperature using polar organic electrolytes. The polymer film to be studied is directly deposited onto the surface of a platinum wire acting as the working electrode. The three-electrode cylindrical cell design with mutual arrangement of the electrodes, inspired by the “ultramicroelectrode concept”, provides enhanced electrochemical response by minimizing ohmic drop while maintaining flexibility for a wide range of experimental setups. The cell performance is demonstrated using a redox conducting polymeric cathode material for organic radical batteries, namely poly[N,N″-bis(3-(4-oxy(2,2,6,6-tetramethylpiperidin-1-oxyl)butoxy)salicylidene)ethylenediiminato nickel(II)], as a test material. Continuous-wave EPR experiments using a portable benchtop spectrometer at a fixed magnetic field allow detecting the material's state of charge, initialisation of oxidation and reduction processes, as well as estimating electrochemical properties. The cell design presented here enables potentiostatic, galvanostatic, and potentiodynamic measurement modes, while offering the possibility of customisation through 3D printing and the use of various electrode materials.
{"title":"Simple setup for in situ electrochemical electron paramagnetic resonance spectroscopy to study organic energy-storage materials","authors":"Anatoliy A. Vereshchagin , Maryam Seif-Eddine , Kaltum Abdiaziz , Maxie M. Roessler , Oleg V. Levin , Jan Behrends","doi":"10.1016/j.jmr.2025.108010","DOIUrl":"10.1016/j.jmr.2025.108010","url":null,"abstract":"<div><div>The design and application of a cost-effective, customisable electrochemical cell suitable for <em>in situ</em> X-band (9–10 GHz) Electron Paramagnetic Resonance (EPR) experiments is demonstrated. The cell is optimized for investigating electrochemical parameters of redox-active polymer films at room temperature using polar organic electrolytes. The polymer film to be studied is directly deposited onto the surface of a platinum wire acting as the working electrode. The three-electrode cylindrical cell design with mutual arrangement of the electrodes, inspired by the “ultramicroelectrode concept”, provides enhanced electrochemical response by minimizing ohmic drop while maintaining flexibility for a wide range of experimental setups. The cell performance is demonstrated using a redox conducting polymeric cathode material for organic radical batteries, namely poly[N,N″-bis(3-(4-oxy(2,2,6,6-tetramethylpiperidin-1-oxyl)butoxy)salicylidene)ethylenediiminato nickel(II)], as a test material. Continuous-wave EPR experiments using a portable benchtop spectrometer at a fixed magnetic field allow detecting the material's state of charge, initialisation of oxidation and reduction processes, as well as estimating electrochemical properties. The cell design presented here enables potentiostatic, galvanostatic, and potentiodynamic measurement modes, while offering the possibility of customisation through 3D printing and the use of various electrode materials.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"383 ","pages":"Article 108010"},"PeriodicalIF":1.9,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789972","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 : 2025-12-17DOI: 10.1016/j.jmr.2025.108008
Bruno Trebbi , Michele Pierigé , Rodrigo Henrique dos Santos Garcia , Francesca Martini , Marco Geppi , Eduardo Ribeiro deAzevedo
A practical and accessible approach for analyzing complex molecular dynamics in heterogeneous systems from the temperature dependence of low-field 1H time-domain NMR signals is presented. Based on Dipolar Filtered Magic Sandwich Echo (DFMSE) experiments, the method can be adapted to any measurement where the fraction of mobile or rigid segments can be monitored as a function of temperature. A theoretical framework based on the Anderson–Weiss model, using analytical expressions, is described, enabling the extraction of activation parameters and their distributions from low-field 1H time-domain NMR data. A theoretical expression for the DFMSE signal as a function of temperature and filter time used in the experiment is derived, and an approximation is proposed to simplify the model while retaining the essential features of the DFMSE–temperature curves. Assuming Arrhenius or Vogel–Fulcher–Tammann (VFT) temperature dependence of correlation times, a relation is obtained linking the curve’s inflection temperature to the filter time, with activation parameters as fitting variables. This allows an initial estimation of activation parameters, later refined by fitting full DFMSE–temperature curves, including a distribution of values. The method is validated by determining activation parameters for motions associated with the glass transition dynamics of atactic polypropylene (aPP), yielding results consistent with previous NMR studies. It is further applied to a styrene–butadiene rubber (SBR) sample, whose parameters were independently obtained by field-cycling NMR, showing good agreement.
{"title":"Accessing molecular motion activation parameters with 1H low-field time-domain NMR: Examples from glass transition in polymers","authors":"Bruno Trebbi , Michele Pierigé , Rodrigo Henrique dos Santos Garcia , Francesca Martini , Marco Geppi , Eduardo Ribeiro deAzevedo","doi":"10.1016/j.jmr.2025.108008","DOIUrl":"10.1016/j.jmr.2025.108008","url":null,"abstract":"<div><div>A practical and accessible approach for analyzing complex molecular dynamics in heterogeneous systems from the temperature dependence of low-field <sup>1</sup>H time-domain NMR signals is presented. Based on Dipolar Filtered Magic Sandwich Echo (DFMSE) experiments, the method can be adapted to any measurement where the fraction of mobile or rigid segments can be monitored as a function of temperature. A theoretical framework based on the Anderson–Weiss model, using analytical expressions, is described, enabling the extraction of activation parameters and their distributions from low-field <sup>1</sup>H time-domain NMR data. A theoretical expression for the DFMSE signal as a function of temperature and filter time used in the experiment is derived, and an approximation is proposed to simplify the model while retaining the essential features of the DFMSE–temperature curves. Assuming Arrhenius or Vogel–Fulcher–Tammann (VFT) temperature dependence of correlation times, a relation is obtained linking the curve’s inflection temperature to the filter time, with activation parameters as fitting variables. This allows an initial estimation of activation parameters, later refined by fitting full DFMSE–temperature curves, including a distribution of values. The method is validated by determining activation parameters for motions associated with the glass transition dynamics of atactic polypropylene (aPP), yielding results consistent with previous NMR studies. It is further applied to a styrene–butadiene rubber (SBR) sample, whose parameters were independently obtained by field-cycling NMR, showing good agreement.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"382 ","pages":"Article 108008"},"PeriodicalIF":1.9,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145784155","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}
<div><div>The majority of chemical elements can be observed by NMR only through half-integer quadrupolar nuclei with spin <em>S</em> = 3/2, 5/2, 7/2 or 9/2. As a result, probing the proximities between these isotopes and protons is crucial for investigating the structure of numerous hydrogen-containing materials, including heterogeneous catalysts, pharmaceuticals, nanostructured materials, etc. These experiments must be conducted under magic-angle spinning (MAS) conditions to resolve the different chemical environments. In particular, different variants of the <sup>1</sup>H → <em>S</em> through-space refocused INEPT (<em>D</em>-RINEPT) sequence have been proposed to probe long-range proximities between protons and half-integer quadrupolar nuclei. These pulse sequences differ by the employed heteronuclear dipolar recoupling scheme as well as the method used to refocus the chemical shift anisotropy of protons during the defocusing and refocusing periods. Some of the most efficient <em>D</em>-RINEPT variants that have been reported so far, include (i) that employing the symmetry-based supercycled <span><math><mi>SR</mi><msubsup><mn>4</mn><mn>1</mn><mn>2</mn></msubsup></math></span> recoupling built from adiabatic inversion pulses incorporated into two spin-echoes and (ii) that using wPMRR (windowed Phase-Modulated Rotary Resonance) recoupling combined with two dipolar-echoes. In particular, the former has been used to enhance the sensitivity of NMR detection of quadrupolar isotopes via indirect DNP (Dynamic Nuclear Polarization) via protons. Nevertheless, there is a lack of comparative studies of these <em>D</em>-RINEPT variants in the literature. In the present study, we introduce new variants of this general scheme, exploring the incorporation of windowed basic elements into the <span><math><mi>R</mi><msubsup><mn>4</mn><mn>1</mn><mn>2</mn></msubsup></math></span> recoupling, and the application of these novel recoupling sequences into dipolar-echo instead of spin-echo refocusing. The efficiencies of these novel <em>D</em>-RINEPT sequences are compared with the existing ones as well as to that of CPMAS (Cross-Polarization under MAS). This experimental comparison is performed at 18.8 T with different MAS frequencies, ν<sub>R</sub> = 10, 20, and 50 kHz, for <sup>1</sup>H → <sup>27</sup>Al and <sup>1</sup>H → <sup>35</sup>Cl polarization transfers in γ-Al<sub>2</sub>O<sub>3</sub> and <span>l</span>-histidine·HCl·H<sub>2</sub>O, respectively. The first sample features moderate <sup>1</sup>H–<sup>1</sup>H dipolar interactions, whereas large <sup>1</sup>H–<sup>1</sup>H couplings are present in the second. We demonstrate that at ν<sub>R</sub> ≤ 20–25 kHz, the most efficient <em>D</em>-RINEPT variant is that employing on <sup>1</sup>H channel two spin-echoes incorporating (i) the <span><math><mi>SR</mi><msubsup><mn>4</mn><mn>1</mn><mn>2</mn></msubsup></math></span> recoupling built from adiabatic pulses, (ii) two composite pulses and (iii) continuous-wave
{"title":"Transfer of magnetization from 1H to half-integer quadrupolar nuclei in solids: comparison of different through-space INEPT variants","authors":"Lixin Liang , Yury G. Kolyagin , Julien Trébosc , Guangjin Hou , Olivier Lafon , Hiroki Nagashima , Jean-Paul Amoureux","doi":"10.1016/j.jmr.2025.108009","DOIUrl":"10.1016/j.jmr.2025.108009","url":null,"abstract":"<div><div>The majority of chemical elements can be observed by NMR only through half-integer quadrupolar nuclei with spin <em>S</em> = 3/2, 5/2, 7/2 or 9/2. As a result, probing the proximities between these isotopes and protons is crucial for investigating the structure of numerous hydrogen-containing materials, including heterogeneous catalysts, pharmaceuticals, nanostructured materials, etc. These experiments must be conducted under magic-angle spinning (MAS) conditions to resolve the different chemical environments. In particular, different variants of the <sup>1</sup>H → <em>S</em> through-space refocused INEPT (<em>D</em>-RINEPT) sequence have been proposed to probe long-range proximities between protons and half-integer quadrupolar nuclei. These pulse sequences differ by the employed heteronuclear dipolar recoupling scheme as well as the method used to refocus the chemical shift anisotropy of protons during the defocusing and refocusing periods. Some of the most efficient <em>D</em>-RINEPT variants that have been reported so far, include (i) that employing the symmetry-based supercycled <span><math><mi>SR</mi><msubsup><mn>4</mn><mn>1</mn><mn>2</mn></msubsup></math></span> recoupling built from adiabatic inversion pulses incorporated into two spin-echoes and (ii) that using wPMRR (windowed Phase-Modulated Rotary Resonance) recoupling combined with two dipolar-echoes. In particular, the former has been used to enhance the sensitivity of NMR detection of quadrupolar isotopes via indirect DNP (Dynamic Nuclear Polarization) via protons. Nevertheless, there is a lack of comparative studies of these <em>D</em>-RINEPT variants in the literature. In the present study, we introduce new variants of this general scheme, exploring the incorporation of windowed basic elements into the <span><math><mi>R</mi><msubsup><mn>4</mn><mn>1</mn><mn>2</mn></msubsup></math></span> recoupling, and the application of these novel recoupling sequences into dipolar-echo instead of spin-echo refocusing. The efficiencies of these novel <em>D</em>-RINEPT sequences are compared with the existing ones as well as to that of CPMAS (Cross-Polarization under MAS). This experimental comparison is performed at 18.8 T with different MAS frequencies, ν<sub>R</sub> = 10, 20, and 50 kHz, for <sup>1</sup>H → <sup>27</sup>Al and <sup>1</sup>H → <sup>35</sup>Cl polarization transfers in γ-Al<sub>2</sub>O<sub>3</sub> and <span>l</span>-histidine·HCl·H<sub>2</sub>O, respectively. The first sample features moderate <sup>1</sup>H–<sup>1</sup>H dipolar interactions, whereas large <sup>1</sup>H–<sup>1</sup>H couplings are present in the second. We demonstrate that at ν<sub>R</sub> ≤ 20–25 kHz, the most efficient <em>D</em>-RINEPT variant is that employing on <sup>1</sup>H channel two spin-echoes incorporating (i) the <span><math><mi>SR</mi><msubsup><mn>4</mn><mn>1</mn><mn>2</mn></msubsup></math></span> recoupling built from adiabatic pulses, (ii) two composite pulses and (iii) continuous-wave ","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"383 ","pages":"Article 108009"},"PeriodicalIF":1.9,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145835849","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 : 2025-12-03DOI: 10.1016/j.jmr.2025.108005
Marvin Lenjer , Lena Schwieger , Igor Tkach , Fabian Hecker , Marina Bennati
We present a modification of the Mims Electron-Nuclear DOuble Resonance (ENDOR) experiment that uses microwave (MW) chirp pulses to enable broadband excitation in W-band () Electron Paramagnetic Resonance (EPR) spectroscopy and Fourier transform (FT) of the resulting stimulated echoes. The method is demonstrated on a nitroxide-19F model system and yields two-dimensional spectra that correlate hyperfine couplings with the EPR spectrum. In contrast to standard, time consuming and costly orientation-selective ENDOR measurements, this approach requires just one experiment at a single EPR resonance field position. At the same time, the resolution in the EPR dimension is increased. This provides additional information on the orientation of the hyperfine coupling tensor and enables the direct observation of chemical shielding anisotropy at W-band frequency. We analyze the effect of chirp pulses on the Mims blind spot function using CHirp Echo Epr SpectroscopY (CHEESY). Additionally, we illustrate that FT of spin echoes can be beneficial even without the availability of chirp pulses, using high-power rectangular MW pulses at Q-band (). Overall, our results suggest that the combination of Mims ENDOR spectroscopy with FT of MW echoes can be a valuable method to obtain detailed information on electron-nuclear spin interaction tensors and will be potentially useful to disentangle complex, multi-component ENDOR spectra.
{"title":"Mims Electron-Nuclear Double Resonance (ENDOR) with chirp microwave pulses","authors":"Marvin Lenjer , Lena Schwieger , Igor Tkach , Fabian Hecker , Marina Bennati","doi":"10.1016/j.jmr.2025.108005","DOIUrl":"10.1016/j.jmr.2025.108005","url":null,"abstract":"<div><div>We present a modification of the Mims Electron-Nuclear DOuble Resonance (ENDOR) experiment that uses microwave (MW) chirp pulses to enable broadband excitation in W-band (<span><math><mrow><mn>94</mn><mspace></mspace><mi>GHz</mi></mrow></math></span>) Electron Paramagnetic Resonance (EPR) spectroscopy and Fourier transform (FT) of the resulting stimulated echoes. The method is demonstrated on a nitroxide-<sup>19</sup>F model system and yields two-dimensional spectra that correlate hyperfine couplings with the EPR spectrum. In contrast to standard, time consuming and costly orientation-selective ENDOR measurements, this approach requires just one experiment at a single EPR resonance field position. At the same time, the resolution in the EPR dimension is increased. This provides additional information on the orientation of the hyperfine coupling tensor and enables the direct observation of chemical shielding anisotropy at W-band frequency. We analyze the effect of chirp pulses on the Mims blind spot function using CHirp Echo Epr SpectroscopY (CHEESY). Additionally, we illustrate that FT of spin echoes can be beneficial even without the availability of chirp pulses, using high-power rectangular MW pulses at Q-band (<span><math><mrow><mn>34</mn><mspace></mspace><mi>GHz</mi></mrow></math></span>). Overall, our results suggest that the combination of Mims ENDOR spectroscopy with FT of MW echoes can be a valuable method to obtain detailed information on electron-nuclear spin interaction tensors and will be potentially useful to disentangle complex, multi-component ENDOR spectra.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"382 ","pages":"Article 108005"},"PeriodicalIF":1.9,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145746320","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 : 2025-12-01DOI: 10.1016/j.jmr.2025.108002
Alastair D. Robinson , Jordan A. Ward-Williams , Matthias Appel , Andrew J. Sederman , Mick D. Mantle , Lynn F. Gladden
T is a powerful analytical technique capable of probing motions on the timescale of molecular dynamics. Conventional T approaches are performed on high-field NMR magnets (typically T) and rely on step-by-step data acquisition, resulting in relatively long experiments and acquisitions that are affected by non-negligible internal gradient effects and strict Specific Absorption Rate limits. The work presented herein reports the development of novel one- and two-dimensional Fast-T pulse sequences on a 2 MHz benchtop NMR spectrometer. The developed method enables the observation of fast-relaxing species down to the millisecond timescale through application of a variably-spaced spin-lock duration array with delay spacings as short as 100 s. Fast-T and Fast-T-T pulse sequences have been developed which show significantly faster acquisition relative to conventional T, illustrated with a 6-fold and 25-fold reduction in experiment time respectively. These techniques were demonstrated to be robust and accurate with measured T values for bulk glycerol showing a maximum difference of 5.4% between Fast-T and conventional T experiments. The power of this method is exemplified through the simultaneous observation of multiple relaxation environments within a porous -AlO sample imbibed with an ethanol:water mixture, where T relaxation rates of two orders of magnitude difference (2.4 ms to 370 ms) were captured.
{"title":"Variable spacing Fast-T1ρ for the analysis of fast relaxing species at low-field","authors":"Alastair D. Robinson , Jordan A. Ward-Williams , Matthias Appel , Andrew J. Sederman , Mick D. Mantle , Lynn F. Gladden","doi":"10.1016/j.jmr.2025.108002","DOIUrl":"10.1016/j.jmr.2025.108002","url":null,"abstract":"<div><div><em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span> is a powerful analytical technique capable of probing motions on the timescale of molecular dynamics. Conventional <em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span> approaches are performed on high-field NMR magnets (typically <span><math><mrow><mo>></mo><mn>2</mn></mrow></math></span> T) and rely on step-by-step data acquisition, resulting in relatively long experiments and acquisitions that are affected by non-negligible internal gradient effects and strict Specific Absorption Rate limits. The work presented herein reports the development of novel one- and two-dimensional Fast-<em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span> pulse sequences on a 2 MHz benchtop NMR spectrometer. The developed method enables the observation of fast-relaxing species down to the millisecond timescale through application of a variably-spaced spin-lock duration array with delay spacings as short as 100 <span><math><mi>μ</mi></math></span>s. Fast-<em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span> and Fast-<em>T</em><span><math><msub><mrow></mrow><mrow><mn>1</mn></mrow></msub></math></span>-<em>T</em><span><math><msub><mrow></mrow><mrow><mn>1</mn><mi>ρ</mi></mrow></msub></math></span> pulse sequences have been developed which show significantly faster acquisition relative to conventional <em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span>, illustrated with a 6-fold and 25-fold reduction in experiment time respectively. These techniques were demonstrated to be robust and accurate with measured <em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span> values for bulk glycerol showing a maximum difference of 5.4% between Fast-<em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span> and conventional <em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span> experiments. The power of this method is exemplified through the simultaneous observation of multiple relaxation environments within a porous <span><math><mi>γ</mi></math></span>-Al<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> sample imbibed with an ethanol:water mixture, where <em>T</em><span><math><msub><mrow></mrow><mrow><mi>1ρ</mi></mrow></msub></math></span> relaxation rates of two orders of magnitude difference (2.4 ms to 370 ms) were captured.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"382 ","pages":"Article 108002"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145784160","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 : 2025-11-26DOI: 10.1016/j.jmr.2025.107995
Oxana Tseytlin , Michael Sestito , Timothy D. Eubank , Valery V. Khramtsov , Benoit Driesschaert , Brian A. Boone , Mark Tseytlin
A modular animal bed–resonator assembly (ABRA) platform is presented for multimodal preclinical co-registration of electron paramagnetic resonance imaging (EPRI) and magnetic resonance imaging (MRI). The reconfigurable “Lego-style” design enables effortless exchange and repositioning of resonator components to support a wide range of frequencies and achieve critical coupling conditions, tailored to the animal's type and size. The ABRA platform also addresses the need for stable EPRI of deep-lying organs in small animal disease models, such as pancreatic cancer, using advanced rapid-scan (RS) technology. RS EPRI enhances sensitivity by enabling higher excitation powers without saturating the spin system. However, the use of increased power exacerbates the challenge of maintaining critical coupling throughout the experiment. To improve data acquisition stability, the EPR resonator and coupling loop are constructed from coaxial cable segments, with the electric field uniformly confined between the inner and outer conductors to minimize undesired electric interactions with the animal. Shielding, along with the absence of touch-sensitive components such as lumped capacitors, contributes to stable data acquisition. Fiducial markers integrated into the bed, visible in both modalities, facilitate automated spatial alignment. The 3D-printed bed is designed to be compatible with affordable preclinical small-bore 1 T MRI systems. Co-registration is performed using a standard MATLAB-based image processing workflow that includes segmentation, fiducial selection, and rigid-body transformation. In vivo evaluation of tuning and coupling performance was conducted using mice bearing pancreatic adenocarcinoma or non-tumor-bearing mice. Imaging results, including co-registration performance, are reported for the non-tumor-bearing mice. The ABRA components and data processing using standard MATLAB tools can be easily replicated in laboratories with minimal engineering expertise.
提出了一种模块化动物床-谐振器组件（ABRA）平台，用于电子顺磁共振成像（EPRI）和磁共振成像（MRI）的多模态临床前联合注册。可重新配置的“乐高风格”设计可以轻松交换和重新定位谐振器组件，以支持广泛的频率范围并实现关键的耦合条件，根据动物的类型和尺寸量身定制。ABRA平台还利用先进的快速扫描（RS）技术，解决了小动物疾病模型（如胰腺癌）中深层器官稳定EPRI的需求。RS EPRI通过使更高的激发功率而不使自旋系统饱和来提高灵敏度。然而，增加功率的使用加剧了在整个实验中保持临界耦合的挑战。为了提高数据采集的稳定性，EPR谐振器和耦合回路由同轴电缆段构成，电场均匀地限制在内外导体之间，以最大限度地减少与动物的不希望的电相互作用。屏蔽，以及没有触摸敏感元件，如集总电容器，有助于稳定的数据采集。基准标记集成到床上，在两种模式下都可见，促进了自动空间对准。3d打印床的设计与价格合理的临床前小口径1 T MRI系统兼容。协同配准是使用标准的基于matlab的图像处理工作流执行的，该工作流包括分割、基准选择和刚体转换。在体内对携带胰腺腺癌的小鼠和未携带肿瘤的小鼠进行了调谐和偶联性能的评估。报道了非荷瘤小鼠的成像结果，包括共配准性能。使用标准MATLAB工具的ABRA组件和数据处理可以在实验室中轻松复制，只需最少的工程专业知识。
{"title":"Reconfigurable animal bed–EPR resonator assembly for multimodal co-registration","authors":"Oxana Tseytlin , Michael Sestito , Timothy D. Eubank , Valery V. Khramtsov , Benoit Driesschaert , Brian A. Boone , Mark Tseytlin","doi":"10.1016/j.jmr.2025.107995","DOIUrl":"10.1016/j.jmr.2025.107995","url":null,"abstract":"<div><div>A modular animal bed–resonator assembly (ABRA) platform is presented for multimodal preclinical co-registration of electron paramagnetic resonance imaging (EPRI) and magnetic resonance imaging (MRI). The reconfigurable “Lego-style” design enables effortless exchange and repositioning of resonator components to support a wide range of frequencies and achieve critical coupling conditions, tailored to the animal's type and size. The ABRA platform also addresses the need for stable EPRI of deep-lying organs in small animal disease models, such as pancreatic cancer, using advanced rapid-scan (RS) technology. RS EPRI enhances sensitivity by enabling higher excitation powers without saturating the spin system. However, the use of increased power exacerbates the challenge of maintaining critical coupling throughout the experiment. To improve data acquisition stability, the EPR resonator and coupling loop are constructed from coaxial cable segments, with the electric field uniformly confined between the inner and outer conductors to minimize undesired electric interactions with the animal. Shielding, along with the absence of touch-sensitive components such as lumped capacitors, contributes to stable data acquisition. Fiducial markers integrated into the bed, visible in both modalities, facilitate automated spatial alignment. The 3D-printed bed is designed to be compatible with affordable preclinical small-bore 1 T MRI systems. Co-registration is performed using a standard MATLAB-based image processing workflow that includes segmentation, fiducial selection, and rigid-body transformation. In vivo evaluation of tuning and coupling performance was conducted using mice bearing pancreatic adenocarcinoma or non-tumor-bearing mice. Imaging results, including co-registration performance, are reported for the non-tumor-bearing mice. The ABRA components and data processing using standard MATLAB tools can be easily replicated in laboratories with minimal engineering expertise.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"382 ","pages":"Article 107995"},"PeriodicalIF":1.9,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145650651","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 : 2025-11-17DOI: 10.1016/j.jmr.2025.107993
Kahinga Kamau , Elzbieta Masiewicz , Pedro José Sebastião , Danuta Kruk
Aiming to reveal the dynamical properties of highly concentrated protein–water systems and validating models of motion, 1H spin-lattice and spin-spin relaxation experiments were performed for myoglobin – H2O (40 % wt. of myoglobin) mixture versus temperature, from 268 K to 310 K. The spin-lattice relaxation studies were conducted using Fast Field Cycling (FFC) NMR relaxometry, in the frequency range from 10 kHz to 20 MHz. The comprehensive set of relaxation data was interpreted in terms of a superposition of relaxation contributions expressed in terms of Lorentzian spectral densities and corresponding to the time scales of the order of 10−6 s, 10−8–10−7 s and 10−9–10−8 s. The model was validated against the 1H spin-spin relaxation data obtained from Time Domain (TD) NMR experiments at 18.5 MHz. The studies were complemented by 1H spin-lattice (FFC NMR and TD NMR) and spin-spin (TD NMR) relaxation experiments for myoglobin – D2O (40 % wt. of myoglobin) mixture. Bi-exponential spin-spin relaxation processes were observed for both myoglobin – H2O and myoglobin – D2O mixtures. A thorough comparison of the spin-lattice relaxation and spin-spin relaxation rates (both components) for the H2O and D2O containing mixtures led to the conclusion that the fast component of the spin-spin relaxation process originates from the pool of 1H nuclei of myoglobin and is associated with slow dynamics of the protein, while the slow component of the spin-spin relaxation is a counterpart of the spin-lattice relaxation process (observed by FFC NMR and TD NMR) and they both reflect the dynamics of water molecules strongly bound to myoglobin (for myoglobin – H2O) and a similar dynamics of myoglobin (for myoglobin – D2O).
{"title":"Dynamics of protein–water mixtures: insight from combined 1H spin-lattice and spin-spin relaxation studies of myoglobin","authors":"Kahinga Kamau , Elzbieta Masiewicz , Pedro José Sebastião , Danuta Kruk","doi":"10.1016/j.jmr.2025.107993","DOIUrl":"10.1016/j.jmr.2025.107993","url":null,"abstract":"<div><div>Aiming to reveal the dynamical properties of highly concentrated protein–water systems and validating models of motion, <sup>1</sup>H spin-lattice and spin-spin relaxation experiments were performed for myoglobin – H<sub>2</sub>O (40 % wt. of myoglobin) mixture versus temperature, from 268 K to 310 K. The spin-lattice relaxation studies were conducted using Fast Field Cycling (FFC) NMR relaxometry, in the frequency range from 10 kHz to 20 MHz. The comprehensive set of relaxation data was interpreted in terms of a superposition of relaxation contributions expressed in terms of Lorentzian spectral densities and corresponding to the time scales of the order of 10<sup>−6</sup> s, 10<sup>−8</sup>–10<sup>−7</sup> s and 10<sup>−9</sup>–10<sup>−8</sup> s. The model was validated against the <sup>1</sup>H spin-spin relaxation data obtained from Time Domain (TD) NMR experiments at 18.5 MHz. The studies were complemented by <sup>1</sup>H spin-lattice (FFC NMR and TD NMR) and spin-spin (TD NMR) relaxation experiments for myoglobin – D<sub>2</sub>O (40 % wt. of myoglobin) mixture. Bi-exponential spin-spin relaxation processes were observed for both myoglobin – H<sub>2</sub>O and myoglobin – D<sub>2</sub>O mixtures. A thorough comparison of the spin-lattice relaxation and spin-spin relaxation rates (both components) for the H<sub>2</sub>O and D<sub>2</sub>O containing mixtures led to the conclusion that the fast component of the spin-spin relaxation process originates from the pool of <sup>1</sup>H nuclei of myoglobin and is associated with slow dynamics of the protein, while the slow component of the spin-spin relaxation is a counterpart of the spin-lattice relaxation process (observed by FFC NMR and TD NMR) and they both reflect the dynamics of water molecules strongly bound to myoglobin (for myoglobin – H<sub>2</sub>O) and a similar dynamics of myoglobin (for myoglobin – D<sub>2</sub>O).</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"382 ","pages":"Article 107993"},"PeriodicalIF":1.9,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145663020","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 : 2025-11-13DOI: 10.1016/j.jmr.2025.107992
Dmitrii Tikhonenko , Kaizad Rustomji , Christophe Vilmen , Arnaud Durand , Georges Nouari , Stefan Enoch , David Bendahan , Redha Abdeddaim , Marc Dubois
Wireless passive resonators have been developed to inductively couple to the birdcage body coil. Such systems have been explored in the form of ceramic resonators with high permittivity but also with metamaterial or metasurface devices that can exhibit resonant behaviour at a given Larmor frequency. The resonant focusing of the radiofrequency field is used to lower the input power during transmission and improve the sensitivity of the body coil during reception. The gain is only obtained in a limited volume located within or close to the resonant structure. Typically, such passive devices do not support parallel imaging and demonstrated limited SNR enhancement compared to dense multichannel receive arrays. Nonetheless, these resonators have seen recent development with applications to wrist or breast MRI mostly in 1.5 T MRI scanners. Here we propose to design, build, and study a metasolenoid resonator operating at 3 T. The metasolenoid was characterized on phantom to validate the B1 efficiency increase with respect to the birdcage polarization excitation. We reported a high B1 efficiency gain for circularly (3.2-fold) and linearly (5.8-fold) polarized excitation. Consequently, and according to analytical calculations, we demonstrated that when excited with linearly polarized excitation, the metasolenoid had a B1 efficiency 26 % higher when excited by the default circularly polarized excitation. Numerical simulations on voxel model showed that in presence of the resonator the B1 efficiency gain normalized by the maximum local SAR was significantly improved when introducing the metasolenoid but the influence of the excitation polarization was reduced to a few percent.
{"title":"Optimal excitation of single mode resonators: demonstration with a 3 T MRI metasolenoid","authors":"Dmitrii Tikhonenko , Kaizad Rustomji , Christophe Vilmen , Arnaud Durand , Georges Nouari , Stefan Enoch , David Bendahan , Redha Abdeddaim , Marc Dubois","doi":"10.1016/j.jmr.2025.107992","DOIUrl":"10.1016/j.jmr.2025.107992","url":null,"abstract":"<div><div>Wireless passive resonators have been developed to inductively couple to the birdcage body coil. Such systems have been explored in the form of ceramic resonators with high permittivity but also with metamaterial or metasurface devices that can exhibit resonant behaviour at a given Larmor frequency. The resonant focusing of the radiofrequency field is used to lower the input power during transmission and improve the sensitivity of the body coil during reception. The gain is only obtained in a limited volume located within or close to the resonant structure. Typically, such passive devices do not support parallel imaging and demonstrated limited SNR enhancement compared to dense multichannel receive arrays<em>.</em> Nonetheless, these resonators have seen recent development with applications to wrist or breast MRI mostly in 1.5 T MRI scanners. Here we propose to design, build, and study a metasolenoid resonator operating at 3 T. The metasolenoid was characterized on phantom to validate the B<sub>1</sub> efficiency increase with respect to the birdcage polarization excitation. We reported a high B<sub>1</sub> efficiency gain for circularly (3.2-fold) and linearly (5.8-fold) polarized excitation. Consequently, and according to analytical calculations, we demonstrated that when excited with linearly polarized excitation, the metasolenoid had a B<sub>1</sub> efficiency 26 % higher when excited by the default circularly polarized excitation. Numerical simulations on voxel model showed that in presence of the resonator the B<sub>1</sub> efficiency gain normalized by the maximum local SAR was significantly improved when introducing the metasolenoid but the influence of the excitation polarization was reduced to a few percent.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"382 ","pages":"Article 107992"},"PeriodicalIF":1.9,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145546583","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 : 2025-10-31DOI: 10.1016/j.jmr.2025.107991
Kathy Sharon Isaac , Phuong Mai Le , Theodore Street , Akila Wijerathna-Yapa , Stanislav Sokolenko
Quantitative NMR is widely utilized in isotopic ratio measurement for determining the origins and authenticity of chemical compounds. Achieving high precision required for such analyses depends on accurately separating signal from noise, which is essential for reliable quantification of resonance peak areas. In this study, we present rnmrfit 2.0, an NMR peak-fitting tool tailored for high precision isotopic analysis. This new version incorporates semi-global peak fitting with automated peak region selection, achieving greater robustness and computational efficiency than previously reported. The newly developed software was used to explore the impact of two common spectral processing techniques, line broadening and zero filling, as well as the choice of baseline span on peak fitting precision. All three were found to have a significant impact on fit precision, with optimal settings for line broadening and zero filling deviating from what is commonly recommended for 13C spectra, at 1–3 Hz and 0.5–1.0, respectively. Compared to commercial tools including TopSpin and MestReNova, rnmrfit demonstrated superior precision and trueness, achieving precision as low as 0.26% for 2H and 0.16% for 13C. The new version of rnmrfit is available as an open-source executable, offering a scalable solution for isotopic analysis with minimal user input, paving the way for more reliable isotopic quantification.
{"title":"Advancing quantitative NMR for high-precision isotopic analysis with rnmrfit 2.0","authors":"Kathy Sharon Isaac , Phuong Mai Le , Theodore Street , Akila Wijerathna-Yapa , Stanislav Sokolenko","doi":"10.1016/j.jmr.2025.107991","DOIUrl":"10.1016/j.jmr.2025.107991","url":null,"abstract":"<div><div>Quantitative NMR is widely utilized in isotopic ratio measurement for determining the origins and authenticity of chemical compounds. Achieving high precision required for such analyses depends on accurately separating signal from noise, which is essential for reliable quantification of resonance peak areas. In this study, we present rnmrfit 2.0, an NMR peak-fitting tool tailored for high precision isotopic analysis. This new version incorporates semi-global peak fitting with automated peak region selection, achieving greater robustness and computational efficiency than previously reported. The newly developed software was used to explore the impact of two common spectral processing techniques, line broadening and zero filling, as well as the choice of baseline span on peak fitting precision. All three were found to have a significant impact on fit precision, with optimal settings for line broadening and zero filling deviating from what is commonly recommended for 13C spectra, at 1–3 Hz and 0.5–1.0, respectively. Compared to commercial tools including TopSpin and MestReNova, rnmrfit demonstrated superior precision and trueness, achieving precision as low as 0.26% for 2H and 0.16% for 13C. The new version of rnmrfit is available as an open-source executable, offering a scalable solution for isotopic analysis with minimal user input, paving the way for more reliable isotopic quantification.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107991"},"PeriodicalIF":1.9,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145524922","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}
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