Journal of magnetic resonance最新文献_第7页

Diamond rotors for high magic angle spinning frequencies 高魔角旋转频率的金刚石转子

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-05-26 DOI: 10.1016/j.jmr.2025.107909

Lauren Schaffer , David Preiss , Ravi Shankar Palani , Nicholas Wiesner , Jiaming Liu , Samuel Strymish , Salima Bahri , Sara Linse , Neil Gershenfeld , Robert G. Griffin

Magic Angle Spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is limited in spectral resolution by the spinning frequency of rotors that hold the analyte. Traditional yttria-stabilized zirconia (YSZ) rotors have mechanical constraints that typically limit spinning frequencies of 0.7 mm rotors to ω_r/2π ∼ 110 kHz. These frequencies are not sufficient to achieve resolution comparable to that of solution NMR, which theoretically requires ω_r/2π > 300 kHz. Building upon prior work that utilized rotary-assisted drilling, we present significant advances in diamond rotor fabrication using a high precision lathe and a centerless laser machining fixture that achieves improved concentricity of the rotor outer and inner diameters and spinning stability. The new crop of diamond rotors, which interface with the Bruker MAS 3 spinning system equivalently or better than commercial rotors, were spun using automatic 0.7 mm profiles. Furthermore, diamond rotors can be emptied and repacked, and we describe a set of 3D-printed centrifuge tools for efficient execution of this process. We evaluate chemical vapor deposition (CVD) versus high-pressure high-temperature (HPHT) diamonds as rotor material and find HPHT preferable. Extended spin stability tests and multidimensional NMR spectra of Aβ₁_–₄₀ demonstrate the robustness and usability of these rotors. These advances pave the way for higher frequency spinning with helium gas in the future, enabling transformative improvements in MAS NMR for biological and material sciences.

魔角旋转（MAS）核磁共振（NMR）光谱学的光谱分辨率受到固定分析物的转子旋转频率的限制。传统的钇稳定氧化锆（YSZ）转子具有机械限制，通常将0.7 mm转子的旋转频率限制在ωr/2π ~ 110 kHz。这些频率不足以达到与溶液核磁共振相当的分辨率，理论上需要ωr/2π >；300千赫。在先前利用旋转辅助钻孔的工作基础上，我们提出了金刚石转子制造的重大进展，使用高精度车床和无心激光加工夹具，实现了转子外径和内径的同心度和旋转稳定性的改善。新一代金刚石转子与布鲁克MAS 3纺丝系统的接口相当于或优于商用转子，使用0.7毫米的自动轮廓进行纺丝。此外，钻石转子可以清空和重新包装，我们描述了一套3d打印离心机工具，用于有效执行这一过程。我们评估了化学气相沉积（CVD）和高压高温（HPHT）钻石作为转子材料，发现高压高温（HPHT）更可取。扩展的自旋稳定性测试和Aβ1-40的多维核磁共振谱证明了这些转子的鲁棒性和可用性。这些进步为未来用氦气进行更高频率旋转铺平了道路，使生物和材料科学的MAS NMR实现了变革性改进。

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引用次数: 0

Evaluating the effect of 1H decoupling on 19F longitudinal relaxation and signal line shape in 5-Fluorotryptophan 评价1H解耦对5-氟色氨酸19F纵向弛豫和信号线形状的影响

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-05-21 DOI: 10.1016/j.jmr.2025.107899

Yuki Toyama , Koh Takeuchi , Ichio Shimada

Fluorine 19 (¹⁹F) in aromatic rings serves as a useful spin probe for studying the structure, dynamics, and intermolecular interactions of biomolecules and small-molecule ligands. Although ¹⁹F NMR involving aromatic ¹⁹F probes has a number of applications, quantitative relaxation analyses of these probes remain challenging due to the complexity of ¹H-¹⁹F spin interaction networks. In this study, we investigated ¹H-¹⁹F spin interactions in the 5-fluorotryptophan system, focusing on the effects of ¹H decoupling on ¹⁹F relaxation properties and line shape. We demonstrate that ¹H decoupling significantly slows down the ¹⁹F magnetization recovery process, leading to reduced sensitivity particularly in large proteins. In addition, ¹H decoupling effectively eliminates cross-correlations between ¹⁹F chemical shift anisotropy and ¹H-¹⁹F dipole-dipole interactions, resolving the asymmetric line shape of the aromatic ¹⁹F signal. Through experimental and theoretical analyses of the ¹H-coupled ¹⁹F spin system, we propose a model that explains these relaxation behaviors. Our results offer practical guidelines for optimizing ¹H decoupling schemes in aromatic ¹⁹F probes, thereby expanding the utility of ¹⁹F NMR.

芳香环中的氟19 （19F）是研究生物分子和小分子配体的结构、动力学和分子间相互作用的有用自旋探针。尽管涉及芳香19F探针的19F核磁共振有许多应用，但由于1H-19F自旋相互作用网络的复杂性，这些探针的定量松弛分析仍然具有挑战性。在本研究中，我们研究了5-氟色氨酸体系中1H-19F自旋相互作用，重点研究了1H解耦对19F弛豫性质和线形的影响。我们证明，1H解耦显著减缓了19F磁化恢复过程，导致敏感性降低，特别是在大蛋白质中。此外，1H去耦有效地消除了19F化学位移各向异性与1H-19F偶极子-偶极子相互作用之间的相互关联，解决了芳香19F信号的不对称线形。通过对h耦合的19F自旋系统的实验和理论分析，我们提出了一个解释这些弛豫行为的模型。我们的结果为优化芳香19F探针的1H解耦方案提供了实用指南，从而扩大了19F NMR的实用性。

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引用次数: 0

PyEPRI: A CPU & GPU compatible python package for electron paramagnetic resonance imaging PyEPRI：一个CPU和GPU兼容python包电子顺磁共振成像

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-05-17 DOI: 10.1016/j.jmr.2025.107891

Rémy Abergel , Sylvain Durand , Yves-Michel Frapart

This work presents the PyEPRI package, an open-source Python package for Electron Paramagnetic Resonance Imaging. The PyEPRI package implements low-level operators, like projection and backprojection, involved in Electron Paramagnetic Resonance (EPR) and also high-level advanced algorithms, like total variation based EPR image reconstruction, for end-users. The package is fully implemented in Python and provides both CPU and GPU computation capabilities, through the libraries Numpy, PyTorch and Cupy. This package comes with a detailed documentation, including precise mathematical definitions and many reproducible demonstration examples and tutorials, making it easy for users with no particular expertise on coding image processing algorithms to get started. This package is also highly modular and only relies on standard data types, as such, it can also be easily used by advanced users to develop new algorithms while benefiting from an optimized computing environment and some rigorously tested operators.

这项工作提出了PyEPRI包，一个开源的Python包电子顺磁共振成像。PyEPRI包实现了电子顺磁共振（EPR）中涉及的低级操作，如投影和反向投影，以及为最终用户提供的高级算法，如基于总变分的EPR图像重建。该包完全用Python实现，并通过库Numpy， PyTorch和Cupy提供CPU和GPU计算能力。该软件包附带了详细的文档，包括精确的数学定义和许多可重复的演示示例和教程，使得没有编码图像处理算法的特殊专业知识的用户可以轻松入门。这个包也是高度模块化的，只依赖于标准数据类型，因此，高级用户也可以很容易地使用它来开发新的算法，同时受益于优化的计算环境和一些经过严格测试的操作符。

引用次数: 0

Easy-to-implement passive shimming approach of Halbach magnet for low-field NMR measurement 用于低场核磁共振测量的易于实现的Halbach磁体被动摆振方法

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-05-16 DOI: 10.1016/j.jmr.2025.107887

Mengjuan Gao , Sihui Luo , Lin Zhu , Lizhi Xiao , Huabing Liu , Guangzhi Liao , Xinman Lv , Hao Chen , Yi Wang

Halbach magnets have been widely employed to NMR instruments due to their low weight, low cost, and minimal leakage of magnetic field. However, field inhomogeneity remains challenge due to discrete magnet rings and manufacturing deviations of the magnetic elements. This paper aims to address this limitation through an effective passive shimming approach, which is considered the first step toward constructing high-homogeneity magnets because of its non-powered and inherently stable characteristics. We focus on the transverse dipole field generated by Halbach magnets and develop an easily implementable linear programming-genetic algorithm (LP-GA) hybrid optimization approach for passive shimming. Our methodology first employs an equivalent magnetic dipole model to calculate the sensitivity matrix of the shim pieces in the Region of Interest (ROI). Then, the LP-GA hybrid optimization algorithm determines the optimal position, number, and thickness of the shim pieces. By combining shim pieces of three different thicknesses (1 mm, 1.5 mm, and 2 mm), we significantly reduce the field inhomogeneity of a 48 mT Halbach magnet system. The effectiveness of our approach is validated through NMR measurements using water samples with copper sulfate at different concentrations, demonstrating an improvement in field homogeneity from approximately 1229 ppm to 320 ppm. The experimental results confirm that the proposed approach effectively enhances magnetic field homogeneity of low-field Halbach magnet systems and could be applied to shimming various Halbach-like magnet arrays.

哈尔巴赫磁体具有重量轻、成本低、磁场泄漏小等优点，已广泛应用于核磁共振仪器中。然而，由于磁环的离散和磁性元件的制造偏差，磁场的不均匀性仍然是一个挑战。本文旨在通过一种有效的被动摆振方法来解决这一限制，由于其无动力和固有稳定的特性，该方法被认为是构建高均匀性磁铁的第一步。针对Halbach磁体产生的横向偶极子场，提出了一种易于实现的线性规划-遗传算法（LP-GA）混合优化方法。我们的方法首先采用等效磁偶极子模型来计算感兴趣区域（ROI）中垫片的灵敏度矩阵。然后，采用LP-GA混合优化算法确定垫片的最佳位置、数量和厚度。通过组合三种不同厚度的薄片（1mm、1.5 mm和2mm），我们显著降低了48mt Halbach磁体系统的场不均匀性。通过使用不同浓度的硫酸铜水样进行核磁共振测量，验证了我们方法的有效性，表明现场均匀性从大约1229 ppm提高到320 ppm。实验结果表明，该方法有效地提高了低场哈尔巴赫磁体系统的磁场均匀性，可用于各种类哈尔巴赫磁体阵列的调光。

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引用次数: 0

Improve robustness to mismatched sampling rate: An alternating deep low-rank approach for exponential function reconstruction and its biomedical magnetic resonance applications 提高对错配采样率的鲁棒性：指数函数重建的交替深度低秩方法及其生物医学磁共振应用

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-05-15 DOI: 10.1016/j.jmr.2025.107898

Yihui Huang , Zi Wang , Xinlin Zhang , Jian Cao , Zhangren Tu , Meijin Lin , Lv Li , Xianwang Jiang , Di Guo , Xiaobo Qu

Undersampling accelerates signal acquisition at the expense of introducing artifacts. Removing these artifacts is a fundamental problem in signal processing and this task is also called signal reconstruction. Through modeling signals as the superimposed exponential functions, deep learning has achieved fast and high-fidelity signal reconstruction by training a mapping from the undersampled exponentials to the fully sampled ones. However, the mismatch, such as undersampling rates (25 % vs. 50 %), anatomical region (knee vs. brain), and contrast configurations (PDw vs. T₂w), between the training and target data will heavily compromise the reconstruction. To overcome this limitation, we propose Alternating Deep Low-Rank (ADLR), which combines deep learning solvers and classic optimization solvers. Experimental validation on the reconstruction of synthetic and real-world biomedical magnetic resonance signals demonstrates that ADLR can effectively alleviate the mismatch issue and achieve lower reconstruction errors than state-of-the-art methods.

欠采样以引入伪影为代价加速信号采集。去除这些伪影是信号处理中的一个基本问题，这项任务也被称为信号重建。通过将信号建模为叠加的指数函数，深度学习通过训练从欠采样指数到全采样指数的映射，实现了快速高保真的信号重建。然而，训练数据和目标数据之间的不匹配，如采样不足率（25% vs 50%）、解剖区域（膝盖vs大脑）和对比配置（PDw vs T2w），将严重影响重建。为了克服这一限制，我们提出了交替深度低秩（ADLR），它结合了深度学习求解器和经典优化求解器。对合成和真实生物医学磁共振信号的重建实验验证表明，ADLR可以有效地缓解不匹配问题，实现比现有方法更低的重建误差。

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引用次数: 0

PP-SNMR measurements using SQUIDs as compact three-component B-field sensors for spatial imaging PP-SNMR测量使用squid作为紧凑的三分量b场传感器进行空间成像

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-05-08 DOI: 10.1016/j.jmr.2025.107888

Tobias Splith , Andreas Chwala , Thomas Hiller , Aaron C. Davis , Raphael Dlugosch , Ronny Stolz , Mike Müller-Petke

We present pre-polarization surface nuclear magnetic resonance (PP-SNMR) measurements performed with a Superconducting QUantum Interference Device (SQUID) magnetometer on water-filled pallet boxes. The SQUID directly detects the three components of the magnetic field (B-field) NMR response, while conventional SNMR experiments would detect its time derivative and most of the time only a single component. Each of the three vector components of the magnetic field NMR response consists of a component oscillating at Larmor frequency and of a non-oscillating component. We extend the general SNMR theory to model the measured signals. For the non-oscillating signal, another magnetic decay with a large amplitude is superimposed on the signal originating from the water-filled boxes, and we were unable to extract the desired signal. For the oscillating signal component, however, we report good agreement between the measured signal and the forward model in amplitude and phase. Measuring all three components of the B-field introduces a sensitivity to lateral inhomogeneities, which we demonstrate by repeating the experiment with one and two emptied boxes.

我们提出了极化前表面核磁共振（PP-SNMR）测量与超导量子干涉装置（SQUID）磁强计在装满水的托盘箱。SQUID直接检测磁场（b场）核磁共振响应的三个分量，而传统的SNMR实验只检测其时间导数，而且大多数时候只检测单一分量。磁场核磁共振响应的三个矢量分量中的每一个都由一个以拉莫尔频率振荡的分量和一个非振荡分量组成。我们扩展了一般的SNMR理论来模拟测量信号。对于非振荡信号，另一个振幅较大的磁衰减叠加在来自充水盒的信号上，我们无法提取所需的信号。然而，对于振荡信号分量，我们报告了测量信号与正演模型在幅度和相位上的良好一致性。测量b场的所有三个分量引入了对横向不均匀性的敏感性，我们通过用一个和两个空盒子重复实验来证明这一点。

{"title":"PP-SNMR measurements using SQUIDs as compact three-component B-field sensors for spatial imaging","authors":"Tobias Splith , Andreas Chwala , Thomas Hiller , Aaron C. Davis , Raphael Dlugosch , Ronny Stolz , Mike Müller-Petke","doi":"10.1016/j.jmr.2025.107888","DOIUrl":"10.1016/j.jmr.2025.107888","url":null,"abstract":"<div><div>We present pre-polarization surface nuclear magnetic resonance (PP-SNMR) measurements performed with a Superconducting QUantum Interference Device (SQUID) magnetometer on water-filled pallet boxes. The SQUID directly detects the three components of the magnetic field (B-field) NMR response, while conventional SNMR experiments would detect its time derivative and most of the time only a single component. Each of the three vector components of the magnetic field NMR response consists of a component oscillating at Larmor frequency and of a non-oscillating component. We extend the general SNMR theory to model the measured signals. For the non-oscillating signal, another magnetic decay with a large amplitude is superimposed on the signal originating from the water-filled boxes, and we were unable to extract the desired signal. For the oscillating signal component, however, we report good agreement between the measured signal and the forward model in amplitude and phase. Measuring all three components of the B-field introduces a sensitivity to lateral inhomogeneities, which we demonstrate by repeating the experiment with one and two emptied boxes.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"376 ","pages":"Article 107888"},"PeriodicalIF":2.0,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143916808","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}

引用次数: 0

Strong field gradients enable NMR-based diffusion measurements for K+, Mg2+, Cl−, and SO42− ions in biomolecular solutions 强场梯度使核磁共振为基础的扩散测量K+， Mg2+， Cl−和SO42−离子在生物分子溶液

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-04-30 DOI: 10.1016/j.jmr.2025.107890

Tianzhi Wang , Daniel Arcos , F. David Doty , B. Montgomery Pettitt , Junji Iwahara

NMR-based diffusion measurements of potassium (K⁺), magnesium (Mg²⁺), chloride (Cl⁻), and sulfate (SO₄²⁻) ions have been challenging even though these ions are biologically important. For these ions, the gyromagnetic ratios of the NMR-active nuclei, ³⁹K, ²⁵Mg, ³⁵Cl, and ³³S, are less than 1/10 of the ¹H gyromagnetic ratio, causing a low sensitivity in NMR detection and a low efficiency in NMR dephasing needed for diffusion measurements. These nuclei also undergo rapid longitudinal and transverse NMR relaxation via the quadrupolar mechanism, severely limiting the effectiveness of NMR-based diffusion measurements. Interactions with biomolecules promote the NMR relaxation of these ions, hindering measurements of the ion diffusion. We demonstrate that, despite these challenges, diffusion of K⁺, Mg²⁺, Cl⁻, and SO₄²⁻ ions in biomolecular solutions can be measured accurately and precisely through use of appropriately designed high-field NMR probe hardware that can generate strong field gradients >1000 G/cm. The NMR-based diffusion coefficients measured at 17.6 T for these ions in the absence of biomolecules agreed well with conductivity-based values in the literature. This consistency supports that ion diffusion along the magnetic field is unaffected by the Lorentz force acting on the ions, as previously predicted. Our data on ion diffusion in solutions of proteins and DNA illuminate the effect of electrostatic interactions on the apparent diffusion coefficients of ions. Thus, high-field NMR probe hardware that can generate strong field gradients opens a new avenue to characterize the dynamic behavior of various ions around biomolecules and their effect on biomolecular electrostatics.

基于核磁共振的钾离子（K+）、镁离子（Mg2+）、氯离子（Cl−）和硫酸盐离子（SO42−）的扩散测量一直具有挑战性，尽管这些离子在生物学上很重要。对于这些离子，核磁共振活性核（39K、25Mg、35Cl和33S）的回旋磁比小于1H回旋磁比的1/10，导致核磁共振检测灵敏度低，扩散测量所需的核磁共振减相效率低。这些核也通过四极性机制经历快速的纵向和横向核磁共振弛豫，严重限制了核磁共振扩散测量的有效性。与生物分子的相互作用促进了这些离子的核磁共振弛豫，阻碍了离子扩散的测量。我们证明，尽管存在这些挑战，但通过使用适当设计的高场核磁共振探针硬件，可以准确地测量生物分子溶液中K+， Mg2+， Cl−和SO42−离子的扩散，该探针硬件可以产生1000 G/cm的强场梯度。在没有生物分子的情况下，这些离子在17.6 T下的核磁共振扩散系数与文献中基于电导率的值很好地一致。这种一致性支持离子沿磁场扩散不受作用在离子上的洛伦兹力的影响，正如先前预测的那样。我们在蛋白质和DNA溶液中离子扩散的数据阐明了静电相互作用对离子表观扩散系数的影响。因此，可以产生强场梯度的高场核磁共振探针硬件为表征生物分子周围各种离子的动态行为及其对生物分子静电的影响开辟了新的途径。

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引用次数: 0

Investigation of 15N-SABRE hyperpolarization at high pressures and in supercritical fluids 高压和超临界流体中的 15N-SABRE 超极化研究

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-04-26 DOI: 10.1016/j.jmr.2025.107876

Xiaoqing Li , Jacob R. Lindale , Loren L. Smith , Warren S. Warren

Signal Amplification By Reversible Exchange (SABRE) is a parahydrogen-based hyperpolarization technique that can generate orders-of-magnitude larger signals than thermal spin polarization within a minute. However, this method is limited by the availability of parahydrogen to the solution. Previous work demonstrated SABRE-derived ¹H hyperpolarization at pressures up to 200 bar and using liquid carbon dioxide as a solvent. Here, we extend this work to demonstrate heteronuclear (¹⁵N) SABRE hyperpolarization using conventional solvents with hydrogen pressures up to 400 bar as well as the possibility of using supercritical CO₂ as the solvent. We demonstrate that in both modes, ¹⁵N hyperpolarization comparable to SABRE-SHEATH may be achieved, providing a route for future optimization efforts as well as scale-up. We also present first steps towards exploring SABRE hyperpolarization of ¹²⁹Xe.

可逆交换信号放大（SABRE）是一种基于对氢的超极化技术，可以在一分钟内产生比热自旋极化大几个数量级的信号。然而，这种方法受到溶液中对氢的可用性的限制。先前的工作证明了sabre衍生的1H超极化在高达200bar的压力下，使用液态二氧化碳作为溶剂。在这里，我们扩展了这项工作，以证明异核（15N） SABRE超极化使用常规溶剂，氢气压力高达400 bar，以及使用超临界CO2作为溶剂的可能性。我们证明，在这两种模式下，都可以实现与SABRE-SHEATH相当的15N超极化，为未来的优化工作和扩大规模提供了一条途径。我们还提出了探索129Xe的SABRE超极化的第一步。

引用次数: 0

Using PELDOR to count spins on multi-nitroxides 用PELDOR来计算多氮氧化物的自旋

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-04-24 DOI: 10.1016/j.jmr.2025.107886

Matthias Bretschneider, Burkhard Endeward, Jörn Plackmeyer, Thomas F. Prisner

We investigated the accuracy and limitation of using the modulation depth of pulsed electron-electron double resonance experiments to count the number of coupled spins. For this purpose, synthesized multi-nitroxide molecules with 2–6 spins were used. We could show that the main limitation on accurately counting larger number of coupled spins at Q-band frequencies is determined by the reproducibility of adjusting and calibrating the pump pulse excitation efficiency. Using broadband sech/tanh or short 10 ns rectangular pump pulses modulation depth suppression effects arising from non-ideal coverage of the dipolar-split signals can be avoided for molecules with intra-molecular spin distances larger than 2 nm. The transverse relaxation times for our model compounds with one to six spins did not depend on the spin number and were all the same. Nevertheless, the signal intensity of the primary Hahn echo signal in a 4-pulse PELDOR sequence decreased strongly with the number of coupled spins. This is due to the dipolar defocusing if more than one spin is excited by the first two pulses at the detection frequency, resulting in a loss of refocused echo intensity of the PELDOR experiments. This effect further reduces the accuracy of using the PELDOR modulation depth for spin counting. Altogether, our results demonstrate that this method is potentially applicable up to hexameric complexes with nitroxides.

我们研究了利用脉冲电子-电子双共振实验的调制深度来计算耦合自旋数的准确性和局限性。为此，合成了具有2-6个自旋的多氮氧化物分子。我们可以证明，在q波段频率上精确计数较大数量的耦合自旋的主要限制是由泵浦脉冲激励效率的调整和校准的再现性决定的。对于分子内自旋距离大于2nm的分子，采用宽带（h/ h）或短（10ns）矩形泵浦脉冲调制深度可避免偶极分裂信号非理想覆盖引起的抑制效应。具有1 ~ 6个自旋的模型化合物的横向弛豫时间不依赖于自旋数，并且都是相同的。然而，在4脉冲PELDOR序列中，主Hahn回波信号的信号强度随着耦合自旋数的增加而明显降低。这是由于在探测频率下，如果前两个脉冲激发多个自旋，则会导致偶极散焦，从而导致PELDOR实验的重聚焦回波强度损失。这种效应进一步降低了使用PELDOR调制深度进行自旋计数的准确性。总之，我们的结果表明，这种方法是潜在的适用于六聚配合物与氮氧化物。

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引用次数: 0

Impact of non-polar solvents in dynamic nuclear polarization at high magnetic fields 非极性溶剂对高磁场下动态核极化的影响

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-04-21 DOI: 10.1016/j.jmr.2025.107885

Tomas Orlando , Huyen Bui , Jhersie Cabigting , Natalie Ibbetson , Johan van Tol , Thierry Dubroca , Xiaoling Wang , Frederic Mentink-Vigier

Dynamic nuclear polarization (DNP) in liquids can enhance NMR signals by up to two orders of magnitude at magnetic fields greater than 9.4 T. The DNP experiment relies on driving electron spin transitions through microwave irradiation of the sample, which requires the solvent/sample to be transparent to microwaves. The physical models describing spin polarization transfer neglect the role of the solvent, despite recent experimental results suggesting that its impact on DNP efficiency can be as much as a factor of three. In this study, we aim to clarify how and why the solvent may affect DNP experiments at high magnetic fields. We examined known systems (¹³C-CCl₄/TEMPO and PPh₃/BDPA) dispersed in CCl₄, heptane, and benzene. By measuring their EPR properties, simulating microwave propagation patterns, and quantitatively assessing the DNP enhancements at 14.1 T, we determined that the choice of non-polar solvent is not critical to the outcome of a DNP experiment. Furthermore, our experimental results and electromagnetic simulations enable us to assess the state-of-the-art capabilities of DNP instruments at high magnetic fields and propose directions for possible future improvements.

液体中的动态核极化（DNP）可以在大于9.4 t的磁场下将核磁共振信号增强两个数量级。DNP实验依赖于通过微波照射样品来驱动电子自旋跃迁，这需要溶剂/样品对微波透明。描述自旋极化转移的物理模型忽略了溶剂的作用，尽管最近的实验结果表明，它对DNP效率的影响可能多达三倍。在本研究中，我们的目的是阐明溶剂如何以及为什么会影响高磁场下的DNP实验。我们研究了分散在CCl4、庚烷和苯中的已知体系（13C-CCl4/TEMPO和PPh3/BDPA）。通过测量它们的EPR特性，模拟微波传播模式，并定量评估在14.1 T下DNP的增强，我们确定非极性溶剂的选择对DNP实验的结果并不重要。此外，我们的实验结果和电磁模拟使我们能够评估DNP仪器在高磁场下的最先进能力，并为未来可能的改进提出方向。

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引用次数: 0