Pub Date : 2025-08-12DOI: 10.1016/j.jmr.2025.107953
Dominik Gendreizig , Christina Elsner , Svetlana Kucher , Gunnar Jeschke , Alistair J. Fielding , Enrica Bordignon
Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labelling provides information on structure and dynamics of biomolecules. Increasing the availability of spin labels with different properties is an elegant way to foster a more accurate analysis of the EPR data in relation to the biological problem investigated. In this study, we present a comparative investigation of labelling efficiency, surface accessibility, site specificity and width of the distance distributions obtained on two proteins with the nitroxide-based bromoacrylaldehyde spin label (BASL) versus the two commercial spin labels MTSL (methanethiosulfonate spin label) and MAP (maleimido proxyl). Based on the predicted distances from a rotamer library approach and on the experimental distance distributions, BASL is shown to provide generally narrower distance distributions compared to the other nitroxide labels. The exquisite surface specificity of BASL with respect to MAP could be successfully exploited to selectively label surface cysteines in proteins containing a high number of native cysteines. In addition, the distinct site-reactivity of BASL and MAP towards two surface-exposed cysteines was leveraged for orthogonal labelling strategies with nitroxide and gadolinium labels.
{"title":"Specificity and reactivity of bromoacrylaldehyde spin labels","authors":"Dominik Gendreizig , Christina Elsner , Svetlana Kucher , Gunnar Jeschke , Alistair J. Fielding , Enrica Bordignon","doi":"10.1016/j.jmr.2025.107953","DOIUrl":"10.1016/j.jmr.2025.107953","url":null,"abstract":"<div><div>Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labelling provides information on structure and dynamics of biomolecules. Increasing the availability of spin labels with different properties is an elegant way to foster a more accurate analysis of the EPR data in relation to the biological problem investigated. In this study, we present a comparative investigation of labelling efficiency, surface accessibility, site specificity and width of the distance distributions obtained on two proteins with the nitroxide-based bromoacrylaldehyde spin label (BASL) versus the two commercial spin labels MTSL (methanethiosulfonate spin label) and MAP (maleimido proxyl). Based on the predicted distances from a rotamer library approach and on the experimental distance distributions, BASL is shown to provide generally narrower distance distributions compared to the other nitroxide labels. The exquisite surface specificity of BASL with respect to MAP could be successfully exploited to selectively label surface cysteines in proteins containing a high number of native cysteines. In addition, the distinct site-reactivity of BASL and MAP towards two surface-exposed cysteines was leveraged for orthogonal labelling strategies with nitroxide and gadolinium labels.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107953"},"PeriodicalIF":1.9,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144860268","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 : 2025-08-08DOI: 10.1016/j.jmr.2025.107938
Marthe Millen , Nicholas Alaniva , Snædís Björgvinsdóttir , Alexander Däpp , Ioannis Gr. Pagonakis , Wolfgang Harneit , Alexander B. Barnes
Dynamic nuclear polarization (DNP) relies on the transfer of electron polarization to nuclei through microwave irradiation and is typically performed under cryogenic magic-angle spinning (MAS) at high magnetic fields. Gyrotrons are commonly used microwave sources in DNP because of their ability to produce high-power microwaves over a broad frequency range. An important step towards a more in-depth understanding of DNP mechanisms and rational optimization of DNP performance is the access to instrumentation, which can provide information about the DNP process. Continuous wave (CW) electron paramagnetic resonance (EPR) can reveal important information on the electron spin system during DNP experiments. Here, we present a dual CW EPR/DNP spectrometer operated under MAS at 100 K and 7 T using a frequency-agile 198 GHz gyrotron. The measured sensitivity for CW EPR at 198 GHz using an MAS stator is 4 1013 spins/(G). To illustrate the electron and nuclear detection capabilities of our setup, DNP profiles and CW EPR spectra of a diamond powder and a trityl sample were recorded under the same conditions, specifically at 100 K and under MAS.
{"title":"Cryogenic magic-angle spinning continuous wave EPR and DNP spectroscopy at 7 T with a gyrotron","authors":"Marthe Millen , Nicholas Alaniva , Snædís Björgvinsdóttir , Alexander Däpp , Ioannis Gr. Pagonakis , Wolfgang Harneit , Alexander B. Barnes","doi":"10.1016/j.jmr.2025.107938","DOIUrl":"10.1016/j.jmr.2025.107938","url":null,"abstract":"<div><div>Dynamic nuclear polarization (DNP) relies on the transfer of electron polarization to nuclei through microwave irradiation and is typically performed under cryogenic magic-angle spinning (MAS) at high magnetic fields. Gyrotrons are commonly used microwave sources in DNP because of their ability to produce high-power microwaves over a broad frequency range. An important step towards a more in-depth understanding of DNP mechanisms and rational optimization of DNP performance is the access to instrumentation, which can provide information about the DNP process. Continuous wave (CW) electron paramagnetic resonance (EPR) can reveal important information on the electron spin system during DNP experiments. Here, we present a dual CW EPR/DNP spectrometer operated under MAS at 100 K and 7 T using a frequency-agile 198 GHz gyrotron. The measured sensitivity for CW EPR at 198 GHz using an MAS stator is 4 <span><math><mo>×</mo></math></span> 10<sup>13</sup> spins/(G<span><math><msqrt><mrow><mi>H</mi><mi>z</mi></mrow></msqrt></math></span>). To illustrate the electron and nuclear detection capabilities of our setup, DNP profiles and CW EPR spectra of a diamond powder and a trityl sample were recorded under the same conditions, specifically at 100 K and under MAS.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107938"},"PeriodicalIF":1.9,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144866960","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 : 2025-08-08DOI: 10.1016/j.jmr.2025.107940
Melisa L. Gimenez , Pablo Jimenez , Leonardo A. Pedraza Pérez , Diana Betancourth , Analia Zwick , Gonzalo A. Álvarez
Neurological diseases often result in changes at microscopic scales in the nervous system, emphasising the need for non-invasive imaging techniques that can quantify these alterations as potential biomarkers for diagnosis. Diffusion-weighted magnetic resonance imaging (DWI), particularly using modulated gradient spin-echo (MGSE) sequences, has significantly advanced in revealing tissue microstructure by probing molecular diffusion. Among the MGSE sequences, the Non-uniform Oscillating Gradient Spin-Echo (NOGSE) sequence generates a contrast based on selective microstructure sizes through a signal decay-shift, rather than probing conventional decay rates. In this study, we evaluate the performance of NOGSE in estimating microstructure sizes using a preclinical MRI scanner. Our results show that while sharp, instantaneous gradient modulations maximise the decay-shift, smooth gradient modulations still provide meaningful contrast. Through a combination of phantom experiments, numerical simulations and information-theoretic analysis, we optimise NOGSE parameters for accurate microstructural size estimation under both sharp and smooth gradient modulations. We identify optimal NOGSE parameters that are compatible with preclinical hardware constraints, providing reliable microstructure size characterisation. Especially smooth gradient modulations expand the range of compatible MRI scanners and are almost suitable for in-vivo applications. These findings represent a step toward developing quantitative imaging tools for probing microstructural features in diffusion-weighted magnetic resonance imaging.
{"title":"Optimisation and impact of gradient waveform modulation on Non-uniform Oscillating Gradient Spin-Echo sequences for microstructural characterisation","authors":"Melisa L. Gimenez , Pablo Jimenez , Leonardo A. Pedraza Pérez , Diana Betancourth , Analia Zwick , Gonzalo A. Álvarez","doi":"10.1016/j.jmr.2025.107940","DOIUrl":"10.1016/j.jmr.2025.107940","url":null,"abstract":"<div><div>Neurological diseases often result in changes at microscopic scales in the nervous system, emphasising the need for non-invasive imaging techniques that can quantify these alterations as potential biomarkers for diagnosis. Diffusion-weighted magnetic resonance imaging (DWI), particularly using modulated gradient spin-echo (MGSE) sequences, has significantly advanced in revealing tissue microstructure by probing molecular diffusion. Among the MGSE sequences, the Non-uniform Oscillating Gradient Spin-Echo (NOGSE) sequence generates a contrast based on selective microstructure sizes through a signal decay-shift, rather than probing conventional decay rates. In this study, we evaluate the performance of NOGSE in estimating microstructure sizes using a preclinical MRI scanner. Our results show that while sharp, instantaneous gradient modulations maximise the decay-shift, smooth gradient modulations still provide meaningful contrast. Through a combination of phantom experiments, numerical simulations and information-theoretic analysis, we optimise NOGSE parameters for accurate microstructural size estimation under both sharp and smooth gradient modulations. We identify optimal NOGSE parameters that are compatible with preclinical hardware constraints, providing reliable microstructure size characterisation. Especially smooth gradient modulations expand the range of compatible MRI scanners and are almost suitable for <em>in-vivo</em> applications. These findings represent a step toward developing quantitative imaging tools for probing microstructural features in diffusion-weighted magnetic resonance imaging.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107940"},"PeriodicalIF":1.9,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842914","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 : 2025-08-05DOI: 10.1016/j.jmr.2025.107934
D.I. Hoult
A new method of creating “shims”, i.e. spherically harmonic fields, is proposed. The technique relies on a direct correspondence between the spatial frequency of sinusoidal azimuthal currents on the surface of an axially aligned cylinder and the degree of the spherically harmonic, axial magnetic fields they create. The sinusoidal current waveform is sampled at at least twice the maximum desired degree/frequency, and the current samples are then applied to the same number of identical conducting arcs, at the same axial position, evenly distributed in a ring. Repetition of this building block at differing axial positions and with appropriate sinusoidal current amplitudes is then used to allow a mix of harmonics of any degree less than or equal to the maximum; the maximum order is determined by the number of axial positions. Calculations are analytical, apart from numerical minimisation of power consumption or mean square current, and correction of minor end effects. Access to the author's Mathematica Notebooks that may help with concepts and calculations is provided. The design holds the promise of more accurate generation of higher orders and degrees than is currently normal, and of easy fabrication with either foil or ribbon cable; the complexity usually associated with construction is essentially transferred to exterior electronics. A novel, conceptual current driver with high efficiency and compliance is also mentioned.
{"title":"Shim coil design by Fourier synthesis","authors":"D.I. Hoult","doi":"10.1016/j.jmr.2025.107934","DOIUrl":"10.1016/j.jmr.2025.107934","url":null,"abstract":"<div><div>A new method of creating “shims”, i.e. spherically harmonic fields, is proposed. The technique relies on a direct correspondence between the spatial frequency of sinusoidal azimuthal currents on the surface of an axially aligned cylinder and the degree of the spherically harmonic, axial magnetic fields they create. The sinusoidal current waveform is sampled at at least twice the maximum desired degree/frequency, and the current samples are then applied to the same number of identical conducting arcs, at the same axial position, evenly distributed in a ring. Repetition of this building block at differing axial positions and with appropriate sinusoidal current amplitudes is then used to allow a mix of harmonics of any degree less than or equal to the maximum; the maximum order is determined by the number of axial positions. Calculations are analytical, apart from numerical minimisation of power consumption or mean square current, and correction of minor end effects. Access to the author's <em>Mathematica</em> Notebooks that may help with concepts and calculations is provided. The design holds the promise of more accurate generation of higher orders and degrees than is currently normal, and of easy fabrication with either foil or ribbon cable; the complexity usually associated with construction is essentially transferred to exterior electronics. A novel, conceptual current driver with high efficiency and compliance is also mentioned.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107934"},"PeriodicalIF":1.9,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145093311","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 : 2025-07-28DOI: 10.1016/j.jmr.2025.107937
Alexander Karabanov , Eugeny Kryukov , Gareth Morris , Jeremy Good
Reference deconvolution, a powerful mathematical tool for removing the effects of imperfections of the main magnetic field on NMR spectra, is revisited in the context of strong static and dynamic field perturbations. The theoretical basis and experimental evidence for the high efficiency of reference deconvolution for strong magnetic field distortions in basic liquid-state one- and two-dimensional NMR are given.
In particular, in 2D NMR, we utilise our observation that a strong static inhomogeneity of the main magnetic field suppresses anti-echo coherence transfer contributions, enabling reference deconvolution to be applied to the remaining echo contributions, in each indirect increment separately, in a manner similar to 1D NMR. We show that, in both 1D and 2D NMR, reference deconvolution enables one to remove the vibrational artefacts of cold head operation in cryogen-free magnets.
This extends the applicability of reference deconvolution in multi-dimensional NMR and advances cryogen-free technology in liquid-state NMR.
{"title":"Removing magnetic field noise from NMR spectra: Reference deconvolution revisited","authors":"Alexander Karabanov , Eugeny Kryukov , Gareth Morris , Jeremy Good","doi":"10.1016/j.jmr.2025.107937","DOIUrl":"10.1016/j.jmr.2025.107937","url":null,"abstract":"<div><div>Reference deconvolution, a powerful mathematical tool for removing the effects of imperfections of the main magnetic field on NMR spectra, is revisited in the context of strong static and dynamic field perturbations. The theoretical basis and experimental evidence for the high efficiency of reference deconvolution for strong magnetic field distortions in basic liquid-state one- and two-dimensional NMR are given.</div><div>In particular, in 2D NMR, we utilise our observation that a strong static inhomogeneity of the main magnetic field suppresses anti-echo coherence transfer contributions, enabling reference deconvolution to be applied to the remaining echo contributions, in each indirect increment separately, in a manner similar to 1D NMR. We show that, in both 1D and 2D NMR, reference deconvolution enables one to remove the vibrational artefacts of cold head operation in cryogen-free magnets.</div><div>This extends the applicability of reference deconvolution in multi-dimensional NMR and advances cryogen-free technology in liquid-state NMR.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107937"},"PeriodicalIF":1.9,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144723392","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 : 2025-07-24DOI: 10.1016/j.jmr.2025.107936
Jinhao Liu , Miutian Wang , Wenchen Wang , Yaohui Wang , Weimin Wang , Feng Liu
This study presents an optimized gradient coil design for a miniature 0.23 T MRI system, aimed at improving absolute and relative magnetic field linearity while accommodating various gradient thicknesses. The design uses a two-step optimization approach: the first step uses Tikhonov regularization to solve a linear problem, providing a stable solution, and the second step refines the solution through nonlinear constrained optimization to further enhance field linearity. An explicit objective function for the inductance matrix of biplanar gradient coils is simplified to enhance computational efficiency. Validation through MATLAB and COMSOL finite element analysis showed excellent performance. Imaging experiments were conducted on small animals (cats and dogs, whose sizes are similar to neonates) while awaiting ethical approval for human neonatal studies. Results demonstrated that all gradient coils achieved absolute and relative linearity errors below 5%. Cubic phantom scans showed slight displacement at the edges, but the structured phantom MRI lines align precisely with the physical markers, indicating negligible geometric distortion. The shield design maintained Z-leakage fields below 5 Gauss, with eddy current compensation achieving a 90% reduction (residual X/Y-gradient 0.05%, Z-gradient 0.20%). T1 and T2-weighted images depicted clear brain structures, while FLAIR and STIR sequences effectively highlighted tissue changes. The proposed gradient coil design method significantly improves absolute and relative linearity while accommodating various gradient thicknesses, demonstrating strong resistance to interference and broad applicability. The comprehensive design-to-manufacturing process ensures optimal parameter selection, resulting in high-quality imaging across multiple MRI sequences. This design demonstrates strong potential for precise in-vivo brain imaging in further NICU applications.
本研究提出了一种优化的梯度线圈设计，用于微型0.23 T MRI系统，旨在提高绝对和相对磁场线性度，同时适应各种梯度厚度。设计采用两步优化方法：第一步采用Tikhonov正则化求解线性问题，提供稳定解，第二步通过非线性约束优化细化解，进一步增强场线性度。为了提高计算效率，对双平面梯度线圈电感矩阵的显式目标函数进行了简化。通过MATLAB和COMSOL有限元分析验证，显示出优异的性能。成像实验是在小动物（猫和狗，它们的大小与新生儿相似）上进行的，同时等待人类新生儿研究的伦理批准。结果表明，所有梯度线圈的绝对线性和相对线性误差均在5%以下。立方体幻象扫描显示边缘有轻微的位移，但结构化的幻象MRI线与物理标记精确对齐，表明几何畸变可以忽略不计。屏蔽设计将z泄漏场保持在5高斯以下，涡流补偿实现了90%的减少(残余X/ y梯度<；0.05%， z梯度<；0.20%)。T1和t2加权图像描绘了清晰的大脑结构，而FLAIR和STIR序列有效地突出了组织变化。所提出的梯度线圈设计方法在适应各种梯度厚度的同时，显著提高了绝对线性度和相对线性度，具有较强的抗干扰性和广泛的适用性。全面的设计到制造过程确保了最佳的参数选择，从而在多个MRI序列中产生高质量的成像。该设计显示了在进一步的新生儿重症监护病房应用中精确的活体脑成像的强大潜力。
{"title":"Gradient coil design for a 0.23 T NICU MRI system using an improved two-step Target-Field Method with enhanced linearity and compact design","authors":"Jinhao Liu , Miutian Wang , Wenchen Wang , Yaohui Wang , Weimin Wang , Feng Liu","doi":"10.1016/j.jmr.2025.107936","DOIUrl":"10.1016/j.jmr.2025.107936","url":null,"abstract":"<div><div>This study presents an optimized gradient coil design for a miniature 0.23 T MRI system, aimed at improving absolute and relative magnetic field linearity while accommodating various gradient thicknesses. The design uses a two-step optimization approach: the first step uses Tikhonov regularization to solve a linear problem, providing a stable solution, and the second step refines the solution through nonlinear constrained optimization to further enhance field linearity. An explicit objective function for the inductance matrix of biplanar gradient coils is simplified to enhance computational efficiency. Validation through MATLAB and COMSOL finite element analysis showed excellent performance. Imaging experiments were conducted on small animals (cats and dogs, whose sizes are similar to neonates) while awaiting ethical approval for human neonatal studies. Results demonstrated that all gradient coils achieved absolute and relative linearity errors below 5%. Cubic phantom scans showed slight displacement at the edges, but the structured phantom MRI lines align precisely with the physical markers, indicating negligible geometric distortion. The shield design maintained Z-leakage fields below 5 Gauss, with eddy current compensation achieving a 90% reduction (residual X/Y-gradient <span><math><mo><</mo></math></span> 0.05%, Z-gradient <span><math><mo><</mo></math></span> 0.20%). T1 and T2-weighted images depicted clear brain structures, while FLAIR and STIR sequences effectively highlighted tissue changes. The proposed gradient coil design method significantly improves absolute and relative linearity while accommodating various gradient thicknesses, demonstrating strong resistance to interference and broad applicability. The comprehensive design-to-manufacturing process ensures optimal parameter selection, resulting in high-quality imaging across multiple MRI sequences. This design demonstrates strong potential for precise <em>in-vivo</em> brain imaging in further NICU applications.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107936"},"PeriodicalIF":2.0,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704306","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 : 2025-07-18DOI: 10.1016/j.jmr.2025.107923
Sebastian J. Richard, Benedict Newling, Bruce J. Balcom
We recently demonstrated a magnetic resonance methodology for measuring and characterizing various pipe flows, using a series of individually-acquired spin echoes at different . The key advantage of our approach lies in the simplicity of the experiment, MR hardware, and data processing. However, acquiring each spin echo separately results in prolonged measurement times. To address this, we employ an echo-train approach to acquire the series of variable spin echoes. By incrementing CPMG echo pulse spacings within the echo train and implementing a four-step phase cycling scheme to suppress coherence pathway effects, we obtain the same echo phase and magnitude response to flow as a function of as in our original method, without requiring individual echo acquisitions. This new approach significantly reduces the number of required experiments, shortening measurement time by a factor of , where is the number of utilized echoes per echo train. Our phase cycling strategy, combined with incremented pulse spacings, enables in our benchtop flow measurement. Validation experiments with Newtonian and shear-thinning fluids confirm that the new echo-train technique yields results consistent with the original approach of acquiring each spin echo separately.
{"title":"Rapid flow characterization measurements using a modified CPMG measurement with incremented echo times, phase cycling and filtering","authors":"Sebastian J. Richard, Benedict Newling, Bruce J. Balcom","doi":"10.1016/j.jmr.2025.107923","DOIUrl":"10.1016/j.jmr.2025.107923","url":null,"abstract":"<div><div>We recently demonstrated a magnetic resonance methodology for measuring and characterizing various pipe flows, using a series of individually-acquired spin echoes at different <span><math><mi>τ</mi></math></span>. The key advantage of our approach lies in the simplicity of the experiment, MR hardware, and data processing. However, acquiring each spin echo separately results in prolonged measurement times. To address this, we employ an echo-train approach to acquire the series of variable <span><math><mi>τ</mi></math></span> spin echoes. By incrementing CPMG echo pulse spacings within the echo train and implementing a four-step phase cycling scheme to suppress coherence pathway effects, we obtain the same echo phase and magnitude response to flow as a function of <span><math><msup><mrow><mi>τ</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> as in our original method, without requiring individual echo acquisitions. This new approach significantly reduces the number of required experiments, shortening measurement time by a factor of <span><math><mrow><mn>1</mn><mo>/</mo><mi>N</mi></mrow></math></span>, where <span><math><mi>N</mi></math></span> is the number of utilized echoes per echo train. Our phase cycling strategy, combined with incremented pulse spacings, enables <span><math><mrow><mi>N</mi><mo>=</mo><mn>3</mn></mrow></math></span> in our benchtop flow measurement. Validation experiments with Newtonian and shear-thinning fluids confirm that the new echo-train technique yields results consistent with the original approach of acquiring each spin echo separately.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107923"},"PeriodicalIF":2.0,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144655402","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 : 2025-07-16DOI: 10.1016/j.jmr.2025.107927
Vishesh Kaushik, Navin Khaneja
The ability to precisely control the spin states of nuclei in an ensemble is critical for advancing NMR spectroscopy. In this paper, we present a technique referred to as Refocused Feedback to construct RF pulses that enable uniform transitions of spin states across the continuous spectrum of chemical shifts. It is used to achieve uniform broadband excitation of nuclei ensemble. The RF pulses are designed based on strategically selected hypothetical initial and final conditions, with the pulse phase iteratively updated according to the feedback control law. The control sequence is then transformed for applications in real systems. This approach ensures uniform excitation across the continuous range of chemical shifts while digitally constructing the pulse sequence from discrete samples.
{"title":"Broadband excitation of nuclei spin by refocused feedback","authors":"Vishesh Kaushik, Navin Khaneja","doi":"10.1016/j.jmr.2025.107927","DOIUrl":"10.1016/j.jmr.2025.107927","url":null,"abstract":"<div><div>The ability to precisely control the spin states of nuclei in an ensemble is critical for advancing NMR spectroscopy. In this paper, we present a technique referred to as <em>Refocused Feedback</em> to construct RF pulses that enable uniform transitions of spin states across the continuous spectrum of chemical shifts. It is used to achieve uniform broadband excitation of nuclei ensemble. The RF pulses are designed based on strategically selected hypothetical initial and final conditions, with the pulse phase iteratively updated according to the feedback control law. The control sequence is then transformed for applications in real systems. This approach ensures uniform excitation across the continuous range of chemical shifts while digitally constructing the pulse sequence from discrete samples.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107927"},"PeriodicalIF":2.0,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695090","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 : 2025-07-11DOI: 10.1016/j.jmr.2025.107935
Emma A. Foley , Joseph F. Thuma , Jacob Mayer , Mita Halder , Wenyu Huang , Frédéric A. Perras , Damien B. Culver , Takeshi Kobayashi
Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a powerful technique for materials characterization, yet its application to air- and moisture-sensitive materials is often hindered by the difficulty in maintaining an inert environment during magic-angle spinning (MAS). This is particularly true for fast-MAS rotors that do not generally provide tight seals. Herein, we present a generalizable approach employing perdeuterated paraffin waxes—n-icosane-d42 and c-dodecane-d24—as protective embedding media to analyze sensitive organometallic catalysts using SSNMR. We demonstrate that these waxes significantly slow oxidative degradation under MAS conditions. Weak background 1H and 13C NMR signals from the waxes are effectively suppressed using double-quantum filtration and cross-polarization techniques. These findings offer a robust method for expanding the scope of SSNMR to air-sensitive systems, with implications for the structural study of reactive materials and catalysts.
{"title":"Protecting air/moisture-sensitive samples using perdeuterated paraffin wax for solid-state NMR experiments under magic-angle spinning","authors":"Emma A. Foley , Joseph F. Thuma , Jacob Mayer , Mita Halder , Wenyu Huang , Frédéric A. Perras , Damien B. Culver , Takeshi Kobayashi","doi":"10.1016/j.jmr.2025.107935","DOIUrl":"10.1016/j.jmr.2025.107935","url":null,"abstract":"<div><div>Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a powerful technique for materials characterization, yet its application to air- and moisture-sensitive materials is often hindered by the difficulty in maintaining an inert environment during magic-angle spinning (MAS). This is particularly true for fast-MAS rotors that do not generally provide tight seals. Herein, we present a generalizable approach employing perdeuterated paraffin waxes—<em>n</em>-icosane-d42 and <em>c</em>-dodecane-d24—as protective embedding media to analyze sensitive organometallic catalysts using SSNMR. We demonstrate that these waxes significantly slow oxidative degradation under MAS conditions. Weak background <sup>1</sup>H and <sup>13</sup>C NMR signals from the waxes are effectively suppressed using double-quantum filtration and cross-polarization techniques. These findings offer a robust method for expanding the scope of SSNMR to air-sensitive systems, with implications for the structural study of reactive materials and catalysts.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107935"},"PeriodicalIF":2.0,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144632715","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 : 2025-06-25DOI: 10.1016/j.jmr.2025.107926
Shengyu Zhang , Yuchen Li , Yansheng Ye , Fang Tian , Xinhua Peng , Riqiang Fu
The feasibility of applying the spin-echo based diagonal peak suppression method in solid-state MAS NMR homonuclear chemical shift correlation experiments is demonstrated. A complete phase cycling is designed to generate sine- and cosine-modulations of the chemical shift difference between the spin-diffused signals, enabling the quadrature detection in the indirect dimension. Meanwhile, all signals not involved in polarization transfer are refocused at the center of the indirect dimension. A data processing algorithm is developed to extract and suppress these spin-echo refocused signals without affecting nearby spin-diffused cross peaks. The processed spectrum is then converted into a conventional two-dimensional homonuclear chemical shift correlation spectrum, free of diagonal peaks. The effectiveness of this method is illustrated using a uniformly 13C-labeled Fmoc-leucine sample and a sample of human Atg8 homolog LC3B, directly conjugated to the amino headgroup of phosphatidylethanolamine (PE) lipids in liposomes.
{"title":"Towards complete suppression of diagonal peaks in solid-state MAS NMR homonuclear chemical shift correlation spectra","authors":"Shengyu Zhang , Yuchen Li , Yansheng Ye , Fang Tian , Xinhua Peng , Riqiang Fu","doi":"10.1016/j.jmr.2025.107926","DOIUrl":"10.1016/j.jmr.2025.107926","url":null,"abstract":"<div><div>The feasibility of applying the spin-echo based diagonal peak suppression method in solid-state MAS NMR homonuclear chemical shift correlation experiments is demonstrated. A complete phase cycling is designed to generate sine- and cosine-modulations of the chemical shift difference between the spin-diffused signals, enabling the quadrature detection in the indirect dimension. Meanwhile, all signals not involved in polarization transfer are refocused at the center of the indirect dimension. A data processing algorithm is developed to extract and suppress these spin-echo refocused signals without affecting nearby spin-diffused cross peaks. The processed spectrum is then converted into a conventional two-dimensional homonuclear chemical shift correlation spectrum, free of diagonal peaks. The effectiveness of this method is illustrated using a uniformly <sup>13</sup>C-labeled Fmoc-leucine sample and a sample of human Atg8 homolog LC3B, directly conjugated to the amino headgroup of phosphatidylethanolamine (PE) lipids in liposomes.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"378 ","pages":"Article 107926"},"PeriodicalIF":2.0,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518107","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号