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}
Pub Date : 2025-10-30DOI: 10.1016/j.jmr.2025.107990
Kaja Tušar , Igor Serša
Spatial encoding in MRI is usually performed using gradient coils that produce a linearly increasing magnetic field Bz in a desired spatial direction such that its gradient is constant. However, it has been shown that spatial encoding in MRI can also be performed with coils that produce nonlinear magnetic fields. In this study, the performance of different types of nonlinear encoding coils, which have a simple design based on the use of a straight wire segment as a building block and a source of a highly nonlinear magnetic field, was experimentally tested in 2D and by simulation in 3D on coils with a nonsymmetric and a symmetric arrangement of these wire segments. All images were reconstructed using our newly presented method, in which the signals are first transformed from the time- to the frequency-domain, yielding a distorted image (spectrum), which is then geometrically and intensity corrected. The quality of the reconstructed images was quantified by comparing them with corresponding reference images obtained with conventional gradient coils. The reconstruction method was accurate for all tested encoding coils and showed that the symmetric coil type produced results that required significantly less corrections compared to the nonsymmetric coil type. Quantitative image quality measurements showed that all encoding coils, despite large differences in the magnetic field of the encoding coils, produce images of similar quality. The results of the study may help advance the design of “gradient” coils towards freer geometries, higher magnetic field gradients or lower inductance and thus faster switching times.
{"title":"Magnetic resonance imaging using a straight wire magnetic field for spatial signal encoding: Imaging verification with 2D experiments and 3D modeling","authors":"Kaja Tušar , Igor Serša","doi":"10.1016/j.jmr.2025.107990","DOIUrl":"10.1016/j.jmr.2025.107990","url":null,"abstract":"<div><div>Spatial encoding in MRI is usually performed using gradient coils that produce a linearly increasing magnetic field <em>B</em><sub><em>z</em></sub> in a desired spatial direction such that its gradient is constant. However, it has been shown that spatial encoding in MRI can also be performed with coils that produce nonlinear magnetic fields. In this study, the performance of different types of nonlinear encoding coils, which have a simple design based on the use of a straight wire segment as a building block and a source of a highly nonlinear magnetic field, was experimentally tested in 2D and by simulation in 3D on coils with a nonsymmetric and a symmetric arrangement of these wire segments. All images were reconstructed using our newly presented method, in which the signals are first transformed from the time- to the frequency-domain, yielding a distorted image (spectrum), which is then geometrically and intensity corrected. The quality of the reconstructed images was quantified by comparing them with corresponding reference images obtained with conventional gradient coils. The reconstruction method was accurate for all tested encoding coils and showed that the symmetric coil type produced results that required significantly less corrections compared to the nonsymmetric coil type. Quantitative image quality measurements showed that all encoding coils, despite large differences in the magnetic field of the encoding coils, produce images of similar quality. The results of the study may help advance the design of “gradient” coils towards freer geometries, higher magnetic field gradients or lower inductance and thus faster switching times.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107990"},"PeriodicalIF":1.9,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145446981","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 : 2025-10-25DOI: 10.1016/j.jmr.2025.107989
Shibani Bhattacharya , Michael Goger , Tassadite Dahmane , Arthur G. Palmer III
High-resolution relaxometry measures nuclear spin longitudinal relaxation rate constants at low static magnetic field, either in the fringe field of a high-field NMR magnet or in an external electromagnetic coil, while polarizing and detecting nuclear magnetization at high field to optimize resolution and sensitivity for biological macromolecules. Detected magnetization depends on relaxation in the low magnetic field and on relaxation during transfer to and from the high magnetic field. Relaxation for backbone amide 15N magnetization in proteins is inherently multiexponential because of dipole–dipole and chemical shift anisotropy interactions with the amide 1H spin and dipole–dipole interactions between the amide 1H spin and 1H remote spins. Nevertheless, relaxation decay profiles for backbone amide 15N spins in proteins are empirically observed to be essentially monoexponential with a single effective relaxation rate constant at magnetic fields as low as 1 T. The present work derives an expression for the effective relaxation rate constant under that assumption that relaxation in the network of dipole–dipole coupled 1H spins is sufficiently rapid. This result enables efficient analysis of relaxometry data without explicit integration of the stochastic Liouville equation for relaxation of the amide N-H moiety and remote amide 1H spins. The approach is validated by relaxometry measurements for 15N-labeled human ubiquitin and E. coli ribonuclease HI. The results obtained with the proposed approach agree well with results obtained using the MINOTAUR program (N. Bolik-Coulon et al., 2023), which integrates the full stochastic Liouville equation.
高分辨率弛豫测量在低静磁场下的核自旋纵向弛豫速率常数，无论是在高场核磁共振磁体的条纹场还是在外部电磁线圈中，同时在高场下极化和检测核磁化，以优化生物大分子的分辨率和灵敏度。检测到的磁化取决于在低磁场中的弛豫和在转移到高磁场和从高磁场的弛豫。由于与酰胺1H自旋的偶极-偶极和化学位移各向异性相互作用以及酰胺1H自旋和1H远自旋之间的偶极-偶极相互作用，蛋白质中主链酰胺15N磁化的弛豫是固有的多指数弛豫。然而，根据经验观察，蛋白质中主链酰胺15N自旋的弛豫衰减曲线基本上是单指数的，在磁场低至1 t时具有单一的有效弛豫速率常数。本研究在假设偶极-偶极耦合1H自旋网络中的弛豫足够快的情况下推导出有效弛豫速率常数的表达式。该结果使弛豫测量数据的有效分析无需显式积分的随机Liouville方程的松弛酰胺N-H部分和远程酰胺1H自旋。通过15n标记的人泛素和大肠杆菌核糖核酸酶HI的松弛测量验证了该方法。该方法得到的结果与MINOTAUR程序（N. Bolik-Coulon et al., 2023）得到的结果非常吻合，该程序集成了完整的随机Liouville方程。
{"title":"A steady-state approach for analysis of high-resolution relaxometry","authors":"Shibani Bhattacharya , Michael Goger , Tassadite Dahmane , Arthur G. Palmer III","doi":"10.1016/j.jmr.2025.107989","DOIUrl":"10.1016/j.jmr.2025.107989","url":null,"abstract":"<div><div>High-resolution relaxometry measures nuclear spin longitudinal relaxation rate constants at low static magnetic field, either in the fringe field of a high-field NMR magnet or in an external electromagnetic coil, while polarizing and detecting nuclear magnetization at high field to optimize resolution and sensitivity for biological macromolecules. Detected magnetization depends on relaxation in the low magnetic field and on relaxation during transfer to and from the high magnetic field. Relaxation for backbone amide <sup>15</sup>N magnetization in proteins is inherently multiexponential because of dipole–dipole and chemical shift anisotropy interactions with the amide <sup>1</sup>H spin and dipole–dipole interactions between the amide <sup>1</sup>H spin and <sup>1</sup>H remote spins. Nevertheless, relaxation decay profiles for backbone amide <sup>15</sup>N spins in proteins are empirically observed to be essentially monoexponential with a single effective relaxation rate constant at magnetic fields as low as 1 T. The present work derives an expression for the effective relaxation rate constant under that assumption that relaxation in the network of dipole–dipole coupled <sup>1</sup>H spins is sufficiently rapid. This result enables efficient analysis of relaxometry data without explicit integration of the stochastic Liouville equation for relaxation of the amide N-H moiety and remote amide <sup>1</sup>H spins. The approach is validated by relaxometry measurements for <sup>15</sup>N-labeled human ubiquitin and <em>E. coli</em> ribonuclease HI. The results obtained with the proposed approach agree well with results obtained using the MINOTAUR program (N. Bolik-Coulon et al., 2023), which integrates the full stochastic Liouville equation.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107989"},"PeriodicalIF":1.9,"publicationDate":"2025-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145423657","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 : 2025-10-14DOI: 10.1016/j.jmr.2025.107988
Chun Him Lee , Meltem Elitaş , Jan G. Korvink , Mazin Jouda
Micro-resonators downsize their resonating structures, reaching frequencies required for electron paramagnetic resonance (EPR) spectroscopy, thus allowing sensitive detection of mass-limited samples. Planar resonators provide accessibility of the sample space, allowing in situ and operando experiments for convenient characterization with access to environmental parameters such as UV radiation, gas and liquid flow, and better temperature gradient control. We report a novel triple-ring resonating structure that exploits the benefits of sample accessibility and its miniaturized structure. It offers three simultaneously operating X-band channels (8 GHz to 11 GHz) with a real-time accessible 50 nL sample volume for each channel, with a maximum spin sensitivity of Spin/Hz1/2. By cascading the ring resonators, we improve the quality factor of each resonance by reflecting and confining the electromagnetic energy by the neighboring rings. The Q-factor of the center resonance at 9.45 GHz with the enhancement of 2 passive reflectors reaches 73. Three relative translations allow a wide range of tuning, matching, suppressing, and isolating the resonances. While the introduced resonator exhibits three resonances only, it can be readily upscaled to feature more resonances, thus opening the door to high-throughput parallel EPR spectroscopy.
{"title":"Sample-accessible multi-resonance X-band EPR triple ring resonator","authors":"Chun Him Lee , Meltem Elitaş , Jan G. Korvink , Mazin Jouda","doi":"10.1016/j.jmr.2025.107988","DOIUrl":"10.1016/j.jmr.2025.107988","url":null,"abstract":"<div><div>Micro-resonators downsize their resonating structures, reaching frequencies required for electron paramagnetic resonance (EPR) spectroscopy, thus allowing sensitive detection of mass-limited samples. Planar resonators provide accessibility of the sample space, allowing <em>in situ</em> and <em>operando</em> experiments for convenient characterization with access to environmental parameters such as UV radiation, gas and liquid flow, and better temperature gradient control. We report a novel triple-ring resonating structure that exploits the benefits of sample accessibility and its miniaturized structure. It offers three simultaneously operating X-band channels (8<!--> <!-->GHz to 11<!--> <!-->GHz) with a real-time accessible 50<!--> <!-->nL sample volume for each channel, with a maximum spin sensitivity of <span><math><mrow><mn>1</mn><mo>.</mo><mn>18</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>8</mn></mrow></msup></mrow></math></span> Spin/Hz<sup>1/2</sup>. By cascading the ring resonators, we improve the quality factor of each resonance by reflecting and confining the electromagnetic energy by the neighboring rings. The Q-factor of the center resonance at 9.45<!--> <!-->GHz with the enhancement of 2 passive reflectors reaches 73. Three relative translations allow a wide range of tuning, matching, suppressing, and isolating the resonances. While the introduced resonator exhibits three resonances only, it can be readily upscaled to feature more resonances, thus opening the door to high-throughput parallel EPR spectroscopy.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107988"},"PeriodicalIF":1.9,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145314445","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 : 2025-10-14DOI: 10.1016/j.jmr.2025.107971
Quirine Krol , Matthew E. Skuntz , Sarah L. Codd , Joseph D. Seymour
Two-phase flow in porous media underpins a wide range of natural and industrial processes, but its transient dynamics remain challenging to capture at the spatiotemporal resolution required to resolve pore-scale phenomena. We present a method for rapid one-dimensional (1D) magnetic resonance imaging (MRI) profiling that simultaneously acquires spin-echo signal intensity and phase angle profiles with spatial and temporal resolution. The technique enables real-time observation of both fluid saturation and velocity fluctuations across a porous medium. We demonstrate its capabilities through three benchmark experiments: (1) controlled drainage and filling of a cylindrical tank, (2) buoyancy-driven rise of oil droplets in water, and (3) drainage and imbibition of a model porous medium. The results reveal dynamic interfacial behavior, velocity fluctuations linked to Haines jumps, and flow-dependent signal attenuation effects. We further analyze the relationship between flow velocity and signal attenuation in porous media using stop-motion dual-echo experiments. Our findings show that rapid magnetic resonance imaging provides a sensitive tool for probing two-phase flow dynamics, with implications for understanding complex fluid behavior in porous materials.
{"title":"Rapid MRI profiling of two-phase flow in porous media","authors":"Quirine Krol , Matthew E. Skuntz , Sarah L. Codd , Joseph D. Seymour","doi":"10.1016/j.jmr.2025.107971","DOIUrl":"10.1016/j.jmr.2025.107971","url":null,"abstract":"<div><div>Two-phase flow in porous media underpins a wide range of natural and industrial processes, but its transient dynamics remain challenging to capture at the spatiotemporal resolution required to resolve pore-scale phenomena. We present a method for rapid one-dimensional (1D) magnetic resonance imaging (MRI) profiling that simultaneously acquires spin-echo signal intensity and phase angle profiles with <span><math><mrow><mn>98</mn><mspace></mspace><mi>μm</mi></mrow></math></span> spatial and <span><math><mrow><mn>20</mn><mspace></mspace><mi>ms</mi></mrow></math></span> temporal resolution. The technique enables real-time observation of both fluid saturation and velocity fluctuations across a porous medium. We demonstrate its capabilities through three benchmark experiments: (1) controlled drainage and filling of a cylindrical tank, (2) buoyancy-driven rise of oil droplets in water, and (3) drainage and imbibition of a model porous medium. The results reveal dynamic interfacial behavior, velocity fluctuations linked to Haines jumps, and flow-dependent signal attenuation effects. We further analyze the relationship between flow velocity and signal attenuation in porous media using stop-motion dual-echo experiments. Our findings show that rapid magnetic resonance imaging provides a sensitive tool for probing two-phase flow dynamics, with implications for understanding complex fluid behavior in porous materials.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107971"},"PeriodicalIF":1.9,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145305131","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 : 2025-10-14DOI: 10.1016/j.jmr.2025.107970
Danil A. Markelov, Alexey S. Kiryutin, Alexandra V. Yurkovskaya
Signal Amplification By Reversible Exchange (SABRE) increases NMR sensitivity using parahydrogen as a source of nuclear spin polarization. In SABRE, the to-be-polarized substrate and dihydrogen in bulk form a transient polarization transfer complex (PTC). This study reports high-field 1H polarization transfer via SABRE induced by selective polychromatic excitation of 1H nuclear spins, avoiding a magnetic field-cycling setup and high-power RF pulses. This enables routine SABRE implementation on standard NMR equipment, including MRI scanners. The proposed polychromatic excitation is efficient for the 1H polarization transfer in the PTCs comprising two weakly coupled hydride 1H nuclei, i.e. with a large chemical shift difference . We show that in a single type of the PTC, coherent high-field 1H polarization transfer is driven by double-RF excitation, i.e. applied at two different frequencies simultaneously. In the general case of several PTCs formed by the substrate molecule, the double-RF excitation allows to selectively induce the 1H polarization transfer in the PTC of interest. To maximize the polarization levels achieved when the substrate forms several types of the PTCs, we propose multi-RF excitation, i.e. applied at more than two 1H frequencies simultaneously, as a generalization of the double-RF approach. The maximum 1H signal enhancements at 9.4 T achieved are as follows: −27 for free nicotinamide (−85 for complex-bound), −21 for free 3-methylpyridine (−105 for complex-bound), −23 for pyridine. Remarkably, for all substrates the 1H signal enhancement exceeds that obtained spontaneously in the high-field: ∼3–9 -fold for the free substrates and ∼10–20-fold for the complex-bound substrates.
{"title":"Polychromatic excitation for 1H SABRE polarization transfer in weakly coupled systems at high field","authors":"Danil A. Markelov, Alexey S. Kiryutin, Alexandra V. Yurkovskaya","doi":"10.1016/j.jmr.2025.107970","DOIUrl":"10.1016/j.jmr.2025.107970","url":null,"abstract":"<div><div>Signal Amplification By Reversible Exchange (SABRE) increases NMR sensitivity using parahydrogen as a source of nuclear spin polarization. In SABRE, the to-be-polarized substrate and dihydrogen in bulk form a transient polarization transfer complex (PTC). This study reports high-field <sup>1</sup>H polarization transfer via SABRE induced by selective polychromatic excitation of <sup>1</sup>H nuclear spins, avoiding a magnetic field-cycling setup and high-power RF pulses. This enables routine SABRE implementation on standard NMR equipment, including MRI scanners. The proposed polychromatic excitation is efficient for the <sup>1</sup>H polarization transfer in the PTCs comprising two weakly coupled hydride <sup>1</sup>H nuclei, i.e. with a large chemical shift difference <span><math><mfrac><mi>γ</mi><mrow><mn>2</mn><mi>π</mi></mrow></mfrac><msub><mi>B</mi><mn>0</mn></msub><mi>Δδ</mi><mo>≫</mo><mfenced><mi>J</mi></mfenced></math></span>. We show that in a single type of the PTC, coherent high-field <sup>1</sup>H polarization transfer is driven by double-RF excitation, i.e. applied at two different frequencies simultaneously. In the general case of several PTCs formed by the substrate molecule, the double-RF excitation allows to selectively induce the <sup>1</sup>H polarization transfer in the PTC of interest. To maximize the polarization levels achieved when the substrate forms several types of the PTCs, we propose multi-RF excitation, i.e. applied at more than two <sup>1</sup>H frequencies simultaneously, as a generalization of the double-RF approach. The maximum <sup>1</sup>H signal enhancements at 9.4 T achieved are as follows: −27 for free nicotinamide (−85 for complex-bound), −21 for free 3-methylpyridine (−105 for complex-bound), −23 for pyridine. Remarkably, for all substrates the <sup>1</sup>H signal enhancement exceeds that obtained spontaneously in the high-field: ∼3–9 -fold for the free substrates and ∼10–20-fold for the complex-bound substrates.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107970"},"PeriodicalIF":1.9,"publicationDate":"2025-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145305069","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 : 2025-10-13DOI: 10.1016/j.jmr.2025.107987
Dominic O. Couillard, Peiyuan Yan, Mohammad Sadegh Zamiri, Bruce J. Balcom, Benedict Newling
Relaxation and relaxation–diffusion correlation measurements have emerged as essential tools for magnetic resonance of materials. Examples of correlation measurements include the –, the –, and the – variants. In this paper, we describe the implementation and validation of a – relaxation correlation measurement. It is shown that this technique effectively distinguishes microscopic environments dominated by local field inhomogeneity from those dominated by nuclear spin–spin interactions. The method is demonstrated in simulation and in glass bead packs.
{"title":"T2–T2∗ relaxation correlation measurement","authors":"Dominic O. Couillard, Peiyuan Yan, Mohammad Sadegh Zamiri, Bruce J. Balcom, Benedict Newling","doi":"10.1016/j.jmr.2025.107987","DOIUrl":"10.1016/j.jmr.2025.107987","url":null,"abstract":"<div><div>Relaxation and relaxation–diffusion correlation measurements have emerged as essential tools for magnetic resonance of materials. Examples of correlation measurements include the <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>–<span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, the <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>–<span><math><mi>D</mi></math></span>, and the <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>–<span><math><msubsup><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>∗</mo></mrow></msubsup></math></span> variants. In this paper, we describe the implementation and validation of a <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>–<span><math><msubsup><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>∗</mo></mrow></msubsup></math></span> relaxation correlation measurement. It is shown that this technique effectively distinguishes microscopic environments dominated by local field inhomogeneity from those dominated by nuclear spin–spin interactions. The method is demonstrated in simulation and in glass bead packs.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107987"},"PeriodicalIF":1.9,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145331486","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 : 2025-10-11DOI: 10.1016/j.jmr.2025.107986
Gennady Khirich , Guilherme Dal Poggetto , Matthew P. Augustine
Spin echoes (SE) refocus chemical shift evolution in weakly coupled homonuclear AX spin systems but leave scalar coupling evolution intact, leading to contamination of the in-phase (IP) echo with anti-phase (AP) coherence. In contrast, the so-called perfect echo (PE), which consists of two SEs flanking a central 90° pulse, can minimize the contribution of AP coherence at the echo, with complete refocusing of homonuclear scalar coupling evolution expected in AX systems based on product operator analysis. However, this precludes the consideration of the effects of differential scalar relaxation (DSR) from the interconversion of IP and AP coherences during a PE or a train of PE echoes (PE-CPMG). In this work, the effects of DSR on an AX spin system subject to a PE or PE-CPMG are considered, and the resulting theoretical spin dynamics are discussed. Exact analytical expressions characterizing the IP and AP coherences of each spin as a function of PE time τPE are derived for a single PE and show relaxation-induced oscillations (RIOs) superimposed onto the decay envelopes of IP coherences along with the concomitant generation of AP coherence, even when pulses are assumed to be ideal, instantaneous, and on-resonance for both spins. Numerical simulations reveal that oscillations in the decay envelop may persist under a PE-CPMG, and that the relaxation of the IP coherences is sensitive to pulse sequence timing in terms of both the repetition rate and total relaxation period. In general, rapid pulsing quenches the AP components and slows down relaxation, though RIOs persist. Notably, specific values of termed dispersion resonances – result in effectively decoupled and non-oscillatory IP decay profiles. We extend our analysis to an AX system undergoing a global two-state exchange process. In direct analogy to DSR, differences between Rex,I and Rex,S – each spin's exchange-induced relaxation enhancements – may induce oscillations in the IP decay profiles and concomitantly generate AP coherence. Moreover, each spin's effective relaxation enhancement is shown to depend on both Rex,I and Rex,S. The analysis of the spin dynamics reported here may be of interest in the further understanding, development, and optimization of PE and PE-CPMG-based pulse sequences, particularly those intended to be used for the accurate measurement and quantification of the underlying dynamics of a homonuclear AX systems undergoing chemical exchange.
{"title":"On the effects of differential scalar relaxation and chemical exchange in perfect echo NMR spectroscopy of AX spin systems","authors":"Gennady Khirich , Guilherme Dal Poggetto , Matthew P. Augustine","doi":"10.1016/j.jmr.2025.107986","DOIUrl":"10.1016/j.jmr.2025.107986","url":null,"abstract":"<div><div>Spin echoes (SE) refocus chemical shift evolution in weakly coupled homonuclear AX spin systems but leave scalar coupling evolution intact, leading to contamination of the in-phase (IP) echo with anti-phase (AP) coherence. In contrast, the so-called perfect echo (PE), which consists of two SEs flanking a central 90° pulse, can minimize the contribution of AP coherence at the echo, with complete refocusing of homonuclear scalar coupling evolution expected in AX systems based on product operator analysis. However, this precludes the consideration of the effects of differential scalar relaxation (DSR) from the interconversion of IP and AP coherences during a PE or a train of PE echoes (PE-CPMG). In this work, the effects of DSR on an AX spin system subject to a PE or PE-CPMG are considered, and the resulting theoretical spin dynamics are discussed. Exact analytical expressions characterizing the IP and AP coherences of each spin as a function of PE time <em>τ</em><sub><em>PE</em></sub> are derived for a single PE and show relaxation-induced oscillations (RIOs) superimposed onto the decay envelopes of IP coherences along with the concomitant generation of AP coherence, even when pulses are assumed to be ideal, instantaneous, and on-resonance for both spins. Numerical simulations reveal that oscillations in the decay envelop may persist under a PE-CPMG, and that the relaxation of the IP coherences is sensitive to pulse sequence timing in terms of both the repetition rate <span><math><mn>1</mn><mo>/</mo><msub><mi>τ</mi><mi>PE</mi></msub></math></span> and total relaxation period. In general, rapid pulsing quenches the AP components and slows down relaxation, though RIOs persist. Notably, specific values of <span><math><mn>1</mn><mo>/</mo><msub><mi>τ</mi><mi>PE</mi></msub></math></span> termed dispersion resonances – result in effectively decoupled and non-oscillatory IP decay profiles. We extend our analysis to an AX system undergoing a global two-state exchange process. In direct analogy to DSR, differences between <em>R</em><sub><em>ex,I</em></sub> and <em>R</em><sub><em>ex,S</em></sub> – each spin's exchange-induced relaxation enhancements – may induce oscillations in the IP decay profiles and concomitantly generate AP coherence. Moreover, each spin's effective relaxation enhancement is shown to depend on both <em>R</em><sub><em>ex,I</em></sub> and <em>R</em><sub><em>ex,S</em></sub>. The analysis of the spin dynamics reported here may be of interest in the further understanding, development, and optimization of PE and PE-CPMG-based pulse sequences, particularly those intended to be used for the accurate measurement and quantification of the underlying dynamics of a homonuclear AX systems undergoing chemical exchange.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107986"},"PeriodicalIF":1.9,"publicationDate":"2025-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145314432","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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