Journal of magnetic resonance最新文献

{"title":"Identifying intermolecular multiple-quantum coherences in ionic liquids","authors":"Yanan Li ,&nbsp;Florin Teleanu ,&nbsp;Alexej Jerschow","doi":"10.1016/j.jmr.2025.107984","DOIUrl":"10.1016/j.jmr.2025.107984","url":null,"abstract":"<div><div>Intermolecular multiple quantum coherences (iMQCs) may arise in isotropic systems with high spin concentrations, of which ionic liquids are an important example. In examining the ¹H, ¹⁹F, and ¹¹B nuclei of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>]), we identified the existence of homonuclear iMQCs for all these nuclei. In addition, for the ¹¹B quadrupolar nuclei, we investigated the possible excitation of intramolecular triple quantum coherences (TQCs) which could in principle arise from the slow tumbling in ionic liquids. These experiments showed that while iMQCs can be excited for ¹¹B, (intramolecular) triple-quantum coherences were not detectable. These findings may help clarifying the ion dynamics and intermolecular interactions in ionic liquids.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107984"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145305109","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}

{"title":"Computationally efficient 4D spectral-spatial EPR imaging","authors":"Mark Tseytlin ,&nbsp;Oxana Tseytlin","doi":"10.1016/j.jmr.2025.107980","DOIUrl":"10.1016/j.jmr.2025.107980","url":null,"abstract":"<div><div>Four-dimensional spectral–spatial imaging (4D SSI) enables noninvasive mapping of spin probes and their microenvironments. Despite its demonstrated utility, 4D SSI remains constrained by substantial computational demands, including large data volumes, the iterative nature of reconstruction algorithms, and significant requirements for memory and computational resources. These resource demands scale cubically with the size of the imaged object. To address these limitations, a set of computational strategies has been developed to improve reconstruction efficiency without compromising image fidelity. These include the use of filtered back projection (FBP) to generate an initial spin concentration map, which serves both as an initial guess for further iterations and as a mask to exclude non-signal voxels. Eliminating these empty voxels significantly reduces the problem size, thereby lowering memory usage and computation time. Additional acceleration is achieved by transforming the 4D reconstruction into a reduced 2D problem, minimizing redundant computation through precomputed values, and employing a compact look-up table for spectral fitting. The resulting workflow, implemented in MATLAB with performance-critical routines compiled as C-based MEX functions, achieves iteration times as low as one minute. Numerical phantom simulations and experimental data from physical phantoms confirm that convergence is substantially improved by excluding non-signal voxels. Among all evaluated approaches, the FBP-based masking of non-signal voxels and the use of a lookup table proved most effective in accelerating algorithm convergence. These improvements enable scalable and computationally efficient 4D SSI suitable for high-resolution, larger-animal preclinical studies and future clinical imaging applications.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107980"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145314455","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}

{"title":"Residual motion artifact removal enables dynamic μMRI of a behaving Pachnoda marginata","authors":"Ajmal Chenakkara ,&nbsp;Mazin Jouda ,&nbsp;Ulrike Wallrabe ,&nbsp;Jan G. Korvink","doi":"10.1016/j.jmr.2025.107954","DOIUrl":"10.1016/j.jmr.2025.107954","url":null,"abstract":"<div><div>Microscopic magnetic resonance imaging, also referred to as <span><math><mi>μ</mi></math></span>MRI, is a non-invasive imaging modality ideal for studying small live model organisms. However, <span><math><mi>μ</mi></math></span>MRI raw data acquisition is inherently sequential and slow in comparison to the biomechanics timescale of the behaving organism, leading to motion artifacts upon image reconstruction. Recently, we have developed an integrated spherical treadmill with a prospectively triggered k-space acquisition technique to provide position consistency for studying live, behaving insect using <span><math><mi>μ</mi></math></span>MRI. Despite this advancement, behaving insects on the treadmill still exhibited motion artifacts due to tethered locomotion being coupled with internal organ dynamics. Here, we are addressing the large-scale non-rigid nature of the abdominal motion of the behaving insect by developing a fully retrospective gating strategy using the motion information obtained from an in-situ computer vision system. Residual motion artifacts persisting after gating are effectively managed through a deep learning technique. We trained a U-Net-based deep convolutional neural network using pairs of simulated motion-corrupted and motion-free images as a supervised image-to-image translation problem. Our results demonstrate that combining retrospective gated <span><math><mi>μ</mi></math></span>MRI reconstruction with a deep learning residual motion compensation technique can significantly reduce the motional artifacts, thereby paving the way for the non-invasive dynamic imaging studies of behaving organisms with 117 <span><math><mi>μ</mi></math></span>m in-plane resolution.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107954"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048178","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}

{"title":"Separate and detailed characterization of signal and noise at low resonance frequencies","authors":"A. Guinness ,&nbsp;Alec A. Beaton ,&nbsp;John M. Franck","doi":"10.1016/j.jmr.2025.107956","DOIUrl":"10.1016/j.jmr.2025.107956","url":null,"abstract":"<div><div>When developing or deploying a Nuclear Magnetic Resonance (NMR) spectrometer, especially for Overhauser Dynamic Nuclear Polarization (ODNP) or other experiments that require low-volume low-field measurements, the ability to mitigate noise and to quantitatively predict signal amplitude prove crucial. A quantitative treatment allows separate analysis of signal and noise and independent optimization of each. In particular, the results here emphasize that clarity and insight come from (1) characterizing the spectral distribution of the noise, and (2) integrating elements of theory and notation originally developed for Electron Spin Resonance (ESR) spectroscopy. Specifically, the spectral noise density “fingerprint spectrum” identifies sources of electromagnetic interference (EMI) and definitively confirms which actions do and do not mitigate the EMI, while the quantitative ratio (<span><math><mi>Λ</mi></math></span>) of <span><math><msub><mrow><mi>B</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> to the square root of the power on the transmission line provides a useful focal point that simplifies the prediction of signal intensity and that decomposes into a few simple but exact factors. Thus, this article provides a relatively comprehensive overview of signal and noise in low-field NMR instruments. The protocol/toolkit introduced here should apply to a wide range of instruments, and give most spectroscopists the freedom to systematically design sensitive NMR hardware even in cases where it must be integrated with multiple other hardware modules (<em>e.g.</em>, an existing ESR system), or where other requirements constrain the design of the NMR hardware. It enables a systematic approach to instrument design and optimization. For the specific X-band ODNP design demonstrated here (and utilized in other laboratories), it facilitates a reduction of the noise power by more than an order of magnitude, and accurately predicts the signal amplitude from measurements of the nutation frequency. Finally, it introduces reasoning to exactly determine the field distribution factor (<span><math><msup><mrow><mi>η</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span>, essentially, a more specific definition of the filling factor) experimentally from <span><math><mi>Λ</mi></math></span> and thus identifies the inefficient distribution of fields in the hairpin loop probe as the main remaining bottleneck for the improvement of low-field, low-volume ODNP signal-to-noise ratio (SNR).</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107956"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145120051","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}

{"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":"2025-12-01","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}

{"title":"A steady-state approach for analysis of high-resolution relaxometry","authors":"Shibani Bhattacharya ,&nbsp;Michael Goger ,&nbsp;Tassadite Dahmane ,&nbsp;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 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 <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":"2025-12-01","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}

{"title":"15N optimal control pulses: an efficient approach to enhance heteronuclear-detected NMR experiments at high magnetic fields","authors":"Marco Schiavina ,&nbsp;David Joseph ,&nbsp;Christian Griesinger ,&nbsp;Isabella C. Felli ,&nbsp;Roberta Pierattelli","doi":"10.1016/j.jmr.2025.107972","DOIUrl":"10.1016/j.jmr.2025.107972","url":null,"abstract":"<div><div>Carbon-13 detected Nuclear Magnetic Resonance (NMR) experiments have become a well-established and powerful tool for investigating a wide variety of biomolecular systems, offering unique insights into structure and dynamics. High field NMR spectrometers offer unprecedented resolution, particularly when working at 1.2 GHz, which is crucial in general and particularly important for samples with crowded NMR spectra. However, operating at such high fields introduces new challenges, including the need for efficient spin manipulations across broad frequency ranges while adhering to the power limitations of modern probes. Optimal control (OC) theory offers a powerful framework for designing Radio-Frequency (RF) pulses that achieve desired spin manipulations with high efficiency, even under strict experimental constraints. In this work, we focus on the implementation of OC-designed ¹⁵N pulses to enhance the performance of ¹³C-detected experiments at 1.2 GHz. Specifically, we demonstrate how these pulses improve both excitation bandwidth and signal sensitivity. The approach is validated using a small, well-folded protein and a more challenging intrinsically disordered protein (IDP) dissolved in a high-salt buffer as commonly required for IDPs' stability. Our results show that ¹⁵N OC pulses provide clear benefits across sample types and conditions, confirming their utility as a robust solution for bandwidth-limited NMR experiments at the highest available magnetic fields.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107972"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145260354","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}

{"title":"Measuring reliable electron spin coherence times with dynamical decoupling sequences that use selective mw pulses","authors":"George Mitrikas ,&nbsp;Rania Giourtsidou","doi":"10.1016/j.jmr.2025.107981","DOIUrl":"10.1016/j.jmr.2025.107981","url":null,"abstract":"<div><div>Dynamical decoupling methods like the Carr-Purcell-Meiboom-Gill (CPMG) or XY4- and XY8-based sequences play a key role in the measurement of reliable electron spin coherence times as they help to disentangle different sources of decoherence. Although these methods are mainly evaluated for their robustness and ability to mitigate pulse imperfections, to date little attention has been paid to the selectivity of the microwave pulses (mw), which is a factor that affects the determination of <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> in two ways: first, unwanted stimulated echoes, which decay with <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>, overlap with desired refocused echoes, resulting in overestimated values of <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>. Second, under selective mw excitation, the amplitude of the different refocused echoes shows an additional time decay even in the absence of relaxation processes. Here, we investigate the characteristics of CPMG, XY4 and XY8-based sequences by performing numerical simulations for a two-level spin system. Using the Liouville space representation of the spin state, we introduce relaxation effects in the simulations. We show that our numerical calculations reproduce well all the features of the experimental echoes and allow for the accurate determination of <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> times without the need to perform tedious phase-cycle protocols to eliminate unwanted signals.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107981"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145260335","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}

{"title":"Polychromatic excitation for 1H SABRE polarization transfer in weakly coupled systems at high field","authors":"Danil A. Markelov,&nbsp;Alexey S. Kiryutin,&nbsp;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 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 <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 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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107970"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","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}

{"title":"On the effects of differential scalar relaxation and chemical exchange in perfect echo NMR spectroscopy of AX spin systems","authors":"Gennady Khirich ,&nbsp;Guilherme Dal Poggetto ,&nbsp;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>_<em>PE</em> 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>_{<em>ex,I</em>} and <em>R</em>_{<em>ex,S</em>} – 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>_{<em>ex,I</em>} and <em>R</em>_{<em>ex,S</em>}. 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":"2025-12-01","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}