Journal of magnetic resonance最新文献

英文中文

Single and double-selective split-inversion pulse and recovery (SIP-R) sequences for targeted T1 relaxation measurements 单和双选择分裂反转脉冲和恢复（SIP-R）序列的目标T1弛豫测量

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-04-17 DOI: 10.1016/j.jmr.2025.107884

Zachary G. Mayes, Yugandhara A.M. Eriyagama, Lingyu Chi, Thomas P. Schuman, Klaus Woelk

Split-Inversion-Pulse and Recovery (SIP-R) is a recently introduced NMR methodology for acquiring spin-lattice relaxation data with a robust decay-to-zero intensity profile as a function of recovery time. This decay-to-zero behavior is particularly advantageous for extracting multiple relaxation times and coefficients using inverse Laplace transformation (ILT) algorithms. In this study, two frequency-selective adaptations of SIP-R are introduced, incorporating either one or two frequency-selective pulses in the SIP-R dual-scan experiment to excite only specific spectral regions. In a test using a non-viscous, small-molecule solution of ethanol in D₂O, both single- and double-selective SIP-R sequences reproduced reasonably well the relaxation times obtained with the non-selective SIP-R method. However, the double-selective SIP-R experiment introduced additional, shorter relaxation times, which were interpreted as artifacts due to the extended duration of the second frequency-selective pulse. Applying the non-selective SIP-R method to a polymer hydrogel enabled the quantitative differentiation of freely moving water molecules (95 %) and water tightly bound to the polymer chains (5 %). The frequency-selective SIP-R variants revealed strong NOE effects between water and polymeric amide resonances, similar to previous findings that suggest strong interactions between water molecules and amine groups in a different type of polymer hydrogel.

分裂-反转脉冲和恢复（SIP-R）是最近引入的一种核磁共振方法，用于获取自旋晶格弛豫数据，该数据具有稳健的衰减到零强度曲线，作为恢复时间的函数。这种衰减到零的行为对于使用逆拉普拉斯变换（ILT）算法提取多个松弛时间和系数特别有利。在本研究中，引入了SIP-R的两种频率选择适应，在SIP-R双扫描实验中加入一个或两个频率选择脉冲，仅激发特定的频谱区域。在一项使用无粘性小分子乙醇溶液的测试中，单选择性和双选择性SIP-R序列都能很好地再现非选择性SIP-R方法获得的弛豫时间。然而，双选择性SIP-R实验引入了额外的、更短的弛豫时间，由于第二个频率选择脉冲的持续时间延长，这被解释为伪像。将非选择性SIP-R方法应用于聚合物水凝胶，可以定量区分自由移动的水分子（95%）和紧密结合在聚合物链上的水分子（5%）。频率选择性SIP-R变异揭示了水和聚合物酰胺共振之间强烈的NOE效应，类似于先前的研究结果，表明水分子和不同类型的聚合物水凝胶中胺基之间存在强烈的相互作用。

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引用次数: 0

Using the amide 15N CEST NMR experiment to study slow exchange between ‘visible’ protein states 使用酰胺15N CEST核磁共振实验研究“可见”蛋白质状态之间的缓慢交换

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-04-12 DOI: 10.1016/j.jmr.2025.107883

Nihar Pradeep Khandave , Ved Prakash Tiwari , Pramodh Vallurupalli

Slow exchange between ‘visible’ protein states is often studied using the two-dimensional ZZ exchange class of magnetisation transfer experiments. However, the cross-peaks that arise due to magnetisation transfer between different states can lead to additional overlap in the two-dimensional ZZ exchange NMR spectrum. To overcome this overlap problem, here we have explored the utility of the ¹⁵N CEST experiment as an alternative to the ¹H^N–¹⁵N ZZ exchange experiment to study exchange between ‘visible’ protein states. In the case of two-state exchange, the ¹H^N–¹⁵N correlation map contains two correlations for each exchanging site, one arising from each state. Thus, two ¹⁵N CEST profiles can be recorded for each of these sites using a single ¹⁵N CEST experiment. We find that site-specific exchange parameters can then be obtained by simultaneously analysing both these ¹⁵N CEST profiles recorded at a single ‘high’ B₁ field supplemented with experimentally derived information regarding the initial magnetisation or as in the case of the ZZ exchange experiment, the minor state population. The utility of the ¹⁵N CEST based approach to characterise exchange between visible protein states is demonstrated by studying the interconversion of the ∼18 kDa T34A mutant of T4 lysozyme between its native state and a minor state populated to ∼21 % (exchange rate ∼5 s⁻¹) at 40 °C.

“可见”蛋白质状态之间的缓慢交换通常使用二维ZZ交换类磁化转移实验进行研究。然而，由于不同状态之间的磁化转移而产生的交叉峰可能导致二维ZZ交换NMR谱中的额外重叠。为了克服这种重叠问题，我们探索了15N CEST实验作为1HN-15N ZZ交换实验的替代方法，以研究“可见”蛋白质状态之间的交换。在双状态交换的情况下，1HN-15N相关图包含每个交换站点的两个相关性，每个状态产生一个相关性。因此，使用单个15N CEST实验，可以为每个站点记录两个15N CEST剖面。我们发现，通过同时分析在单个“高”B1场记录的这两个15N CEST剖面，并辅以实验得出的有关初始磁化的信息，或者像在ZZ交换实验的情况下，小态种群，可以获得特定位置的交换参数。通过研究T4溶菌酶的~ 18 kDa T34A突变体在其天然状态和填充到~ 21%（交换速率~ 5 s−1）的小状态之间的相互转换，证明了基于15N CEST的方法在可见蛋白状态之间交换的效用。

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引用次数: 0

Exact solution of the parameter identification inverse problem for the Bloch–McConnell equations. Longitudinal magnetization Bloch-McConnell方程参数辨识逆问题的精确解。纵向磁化

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-03-30 DOI: 10.1016/j.jmr.2025.107873

Ivan Argatov, Vitaly Kocherbitov

A two-site magnetic exchange model comprising a set of two linear first-order differential Bloch–McConnell equations is considered. The relaxation and exchange behavior is described using a symmetrical form of the general solution derived in the case of longitudinal magnetization for the zero initial conditions. The inverse problem with limited magnetization information has been solved exactly in an analytical explicit form under mild a priori knowledge about the exchange and relaxation parameters.

考虑了一个由两个线性一阶微分Bloch-McConnell方程组成的二元磁交换模型。在零初始条件下，用纵向磁化情况下导出的通解的对称形式描述了弛豫和交换行为。在对交换参数和弛豫参数有少许先验知识的情况下，用解析显式精确地求解了具有有限磁化信息的逆问题。

引用次数: 0

Chemical exchange in unstable emulsions 不稳定乳剂中的化学交换

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-03-28 DOI: 10.1016/j.jmr.2025.107875

Ke Xu, Jörn Schmedt auf der Günne

Nuclear magnetic resonance (NMR) is a routine method to study chemical exchange in reactions and molecular rearrangements in solution. However, when it comes to exchange of molecular species in liquid-liquid, two phase systems like in phase-transfer catalysis, the rate becomes a function of the surface area between two phases, which means that only persistent emulsions could be studied with standard equipment. Unstable emulsions, which rapidly demix, require a continuous application of shear forces by stirring. Here, a setup is described with which unstable emulsions can be produced and studied in-situ by solution NMR spectroscopy. The setup provides sufficient torque and spinning frequency for generating an unstable two-phase water/oil mixture by rapid stirring. The pneumatically driven stirrer in the probe head was designed using ideas borrowed from magic angle sample spinning and a prototype was produced by 3D printing. As proof of concept, the dynamics in an aniline water emulsion over the phase boundary are studied by regular exchange spectroscopy NMR experiments.

核磁共振（NMR）是研究反应中的化学交换和溶液中分子重排的常规方法。然而，当涉及到液-液两相体系中分子种类的交换时，就像在相转移催化中一样，速率变成了两相之间表面积的函数，这意味着只有持久乳液才能用标准设备进行研究。不稳定的乳剂会迅速分解，需要通过搅拌持续施加剪切力。本文介绍了一种制备不稳定乳剂的装置，并通过溶液核磁共振光谱法对其进行了原位研究。该装置提供了足够的扭矩和旋转频率，通过快速搅拌产生不稳定的两相水/油混合物。利用魔角纺丝的思路设计了探针头部的气动搅拌装置，并利用3D打印技术制作了样机。为了证明这一概念，我们用常规的核磁共振交换光谱实验研究了苯胺水乳状液在相边界上的动力学。

引用次数: 0

Cryogenic field-cycling instrument for optical NMR hyperpolarization studies 用于光学核磁共振超极化研究的低温场循环仪器

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-03-28 DOI: 10.1016/j.jmr.2025.107874

Noella D'Souza , Kieren A. Harkins , Cooper Selco , Ushoshi Basumallick , Samantha Breuer , Zhuorui Zhang , Paul Reshetikhin , Marcus Ho , Aniruddha Nayak , Maxwell McAllister , Emanuel Druga , David Marchiori , Ashok Ajoy

Optical dynamic nuclear polarization (DNP) offers an attractive approach to enhancing the sensitivity of nuclear magnetic resonance (NMR) spectroscopy. Efficient, optically-generated electron polarization can be leveraged to operate across a broad range of temperatures and magnetic fields, making it particularly appealing for applications requiring high DNP efficiency or spatial resolution. While a large class of systems hold promise for optical DNP, many candidates display both variable electron polarizability and electron and nuclear T₁ relaxation times as functions of magnetic field and temperature. This necessitates tools capable of studying DNP under diverse experimental conditions. To address this, we introduce a cryogenic field cycling instrument that facilitates optical DNP studies across a wide range of magnetic fields (10 mT–9.4 T) and temperatures (∼10 K–300 K) for wide-bore magnets. Continuous cryogen replenishment enables sustained, long-term operation. Additionally, the system supports the ability to manipulate and probe rapidly hyperpolarized (∼60 s) nuclear spins via pulse sequences involving millions of RF pulses. We describe innovations in the device design and demonstrate its operation on a model system of ¹³C nuclear spins in diamond polarized through optically pumped nitrogen vacancy (NV) centers. We anticipate the use of the instrument for a broad range of optical DNP systems and studies.

光学动态核极化（DNP）是提高核磁共振（NMR）光谱灵敏度的一种有吸引力的方法。利用高效的光学产生的电子极化可以在广泛的温度和磁场范围内工作，这使得它对需要高DNP效率或空间分辨率的应用特别有吸引力。虽然一大类系统有望实现光学DNP，但许多候选系统显示出可变的电子极化率以及电子和核T1弛豫时间作为磁场和温度的函数。这就需要能够在不同实验条件下研究DNP的工具。为了解决这个问题，我们引入了一种低温场循环仪器，该仪器有助于在宽口径磁体的大范围磁场（10 mT-9.4 T）和温度（~ 10 K - 300 K）下进行光学DNP研究。持续的冷冻剂补充可以保证持续、长期的运行。此外，该系统支持通过涉及数百万RF脉冲的脉冲序列操纵和探测快速超极化（~ 60秒）核自旋的能力。我们描述了器件设计上的创新，并在一个通过光泵浦氮空位中心偏振的金刚石13C核自旋模型系统上演示了其操作。我们期望将该仪器用于广泛的光学DNP系统和研究。

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引用次数: 0

A concept of volume wireless receive-only coil for 1.5T MRI 用于1.5T MRI的体积无线接收线圈的概念

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-03-21 DOI: 10.1016/j.jmr.2025.107841

Aleksandr Fedotov , Pavel Tikhonov , Viktor Puchnin , Ekaterina Brui , Anatoliy Levchuk , Ayshat Karaeva , Alena Shchelokova , Georgiy Solomakha , Anna Hurshkainen

Wireless radio frequency coils offer an alternative to conventional cable-connected coils due to their compatibility with multiple vendor MRI systems and reduced electromagnetic interaction with the environment of the MRI scanner. However, wireless coils being inductively coupled with a transceiver body coil require manual input power calibration due to the significant increase of a body coil transmit efficiency locally in the region of interest and disturbance of

B_{1}^{+}

homogeneity complicating routine scanning procedures. This study aims to implement the concept of a wireless receive-only coil for female breast MRI at 1.5T. The approach combines the advantages of wireless coils to increase signal to noise ratio of transceiver body coil in the target region of interest and the ability to perform the automatic reference voltage calibration.

无线射频线圈是传统电缆连接线圈的另一种选择，因为它与多个供应商的MRI系统兼容，并且减少了与MRI扫描仪环境的电磁相互作用。然而，无线线圈与收发器本体线圈电感耦合需要手动输入功率校准，因为本体线圈在感兴趣区域的局部传输效率显着增加，并且B1+均匀性的干扰使常规扫描程序复杂化。本研究旨在实现女性乳房MRI 1.5T无线接收线圈的概念。该方法结合了无线线圈的优点，提高了收发器本体线圈在感兴趣区域的信噪比，并能够进行自动参考电压校准。

引用次数: 0

Design of planar transmission line microwave probes for broadband EPR spectroscopy 宽带EPR光谱用平面传输线微波探头的设计

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-03-18 DOI: 10.1016/j.jmr.2025.107866

Selina Eckel , Julian Nagel , Mazin Jouda , Jan Gerrit Korvink , Ahmet Çağrı Ulusoy

In broadband transmission-based electron paramagnetic resonance (EPR) spectrometers, non-resonant planar microwave probes play a key role, but very few systematic explorations of their design space exist. We develop design guidelines for two common types of transmission lines, microstrip and coplanar waveguide, to achieve a high effective microwave magnetic field strength, which ultimately leads to a more sensitive EPR measurement set-up. We compare the optimized transmission line structures and show that the coplanar waveguide achieves a higher simulated effective magnetic field strength. The simulation results are confirmed by EPR measurements up to a microwave frequency of 45 GHz.

在基于宽带传输的电子顺磁共振（EPR）光谱仪中，非共振平面微波探针起着关键作用，但对其设计空间的系统探索还很少。我们为两种常见类型的传输线，微带和共面波导制定了设计指南，以实现高效的微波磁场强度，最终导致更敏感的EPR测量设置。比较了优化后的传输线结构，结果表明共面波导具有较高的模拟有效磁场强度。仿真结果得到了微波频率为45 GHz的EPR测量结果的验证。

引用次数: 0

NMR of a single nuclear spin detected by a scanning tunnelling microscope 用扫描隧道显微镜探测单个核自旋的核磁共振成像

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-03-11 DOI: 10.1016/j.jmr.2025.107863

Yishay Manassen , Michael Averbukh , Zion Hazan , Yahel Tzuriel , Pino Boscolo , Alexander Shnirman , Baruch Horovitz

We detect a single spin nuclear magnetic resonance (NMR) by monitoring the intensity modulations of a selected hyperfine line in the electron spin resonance (ESR) spectrum. We analyse the power spectrum of the corresponding hyperfine intensity and obtain the nuclear magnetic resonance (NMR) spectrum. Our process also demonstrates ionization of a molecule with the bias voltage of a Scanning Tunnelling Microscope (STM), allowing detection of NMR even in molecules that are non-radical in their neutral state. We have observed this phenomenon in four types of molecules: toluene, triphenylphosphine, TEMPO and adenosine triphosphate (ATP) showing NMR of

^{1}

H, ¹³C, ³¹P and ¹⁴N nuclei. The spectra are detailed and show signatures of the chemical environment, i.e. chemical shifts. A theoretical model to account for these data is outlined.

我们通过监测电子自旋共振（ESR）光谱中选定的超细线的强度调制来检测单自旋核磁共振（NMR）。我们分析了相应超精细强度的功率谱，得到了核磁共振（NMR）谱。我们的过程还演示了用扫描隧道显微镜（STM）的偏置电压电离分子，即使在中性状态的非自由基分子中也可以检测到核磁共振。我们已经在四种类型的分子中观察到这种现象：甲苯、三苯基膦、TEMPO和三磷酸腺苷（ATP），它们的核磁共振显示为1H、13C、31P和14N核。光谱是详细的，显示了化学环境的特征，即化学位移。提出了一个解释这些数据的理论模型。

引用次数: 0

Construction and testing of a high-homogeneity 55 T pulsed magnet for high-field nuclear magnetic resonance measurements 用于高场核磁共振测量的高均匀性55t脉冲磁体的构建和测试

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-03-08 DOI: 10.1016/j.jmr.2025.107862

Wenqi Wei, Luchen Wei, Shunkun Ouyang, Kangjian Luo, Zhuo Wang, Shiyu Liu, Yongkang Luo, Xiaotao Han

High-field nuclear magnetic resonance (NMR) experiments call for the further development of pulsed magnets with a more practical winding structure and higher magnetic field homogeneity. This study presents the construction method and test results of a high-homogeneity pulsed magnet based on an optimized localized split structure. A winding craft using gap spacers was developed for the precise winding of split-gap transition wires. Magnetic field mapping was achieved in a steady-state low field of 32 mT using a Hall probe, with a measured magnetic field inhomogeneity of 198 ± 19 ppm over 1 cm diameter of spherical volume (DSV). The full-width at half-maximum (FWHM) of NMR spectra was adopted as a means of evaluating the magnetic field homogeneity in the pulsed field. In the optimal position, the measured FWHM is 42.2 ± 2.5 ppm at the low field of 7.7 T over a sample volume of 12.6 mm³. At the high field of 50 T, the FWHM decreases to 16.2 ± 0.8 ppm, which is a superior value achieved in similar reported pulsed magnets.

高场核磁共振实验要求进一步开发绕组结构更实用、磁场均匀性更高的脉冲磁体。介绍了一种基于优化局部分裂结构的高均匀性脉冲磁体的构造方法和试验结果。提出了一种利用间隙垫片对开缝过渡丝进行精密绕制的工艺。利用霍尔探针在32 mT的稳态低磁场下实现了磁场映射，在1厘米直径的球形体积（DSV）上测量到的磁场不均匀性为198±19 ppm。采用核磁共振波谱半峰全宽作为评价脉冲场磁场均匀性的手段。在最佳位置，样品体积为12.6 mm3，低场为7.7 T时，测量到的FWHM为42.2±2.5 ppm。在50 T的高场下，FWHM降低到16.2±0.8 ppm，这在同类报道的脉冲磁体中是优越的。

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Relativistic effects on the magnetic shielding in solids: First-principles computation in a plane wave code 固体中磁屏蔽的相对论效应：平面波码的第一性原理计算

IF 2 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-03-07 DOI: 10.1016/j.jmr.2025.107861

J.W. Zwanziger, A.R. Farrant, U. Werner-Zwanziger

For computing the magnetic shielding in solids, density functional theory as implemented in a plane wave basis has proven to be a reasonably accurate and efficient framework, at least for lighter atoms through the third row of the periodic table. In materials with heavier atoms, terms not usually included in the electronic Hamiltonian can become significant, limiting accuracy. Here we derive and implement the zeroth-order regular approximation (ZORA) relativistic terms in the presence of both external magnetic fields and internal nuclear magnetic dipoles, to derive the ZORA-corrected magnetic shielding in the context of periodic boundary conditions and a plane wave basis. We describe our implementation in an open source code, Abinit, and show how it correctly predicts magnetic shieldings in various scenarios, for example the heavy atom next to light atom cases of the III–V semiconductors such as AlSb.

对于计算固体中的磁屏蔽，密度泛函理论在平面波基础上实现已被证明是一个相当准确和有效的框架，至少对于元素周期表第三行较轻的原子。在具有较重原子的材料中，通常不包括在电子哈密顿量中的项可能变得重要，从而限制了精度。本文推导并实现了外磁场和内核磁偶极子存在下的零阶正则逼近（ZORA）相对论性项，从而推导出周期边界条件和平面波基下的ZORA修正磁屏蔽。我们在开源代码Abinit中描述了我们的实现，并展示了它如何正确预测各种情况下的磁屏蔽，例如III-V半导体（如AlSb）的重原子与轻原子相邻的情况。

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