Journal of magnetic resonance最新文献_第5页

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

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

{"title":"Using PELDOR to count spins on multi-nitroxides","authors":"Matthias Bretschneider, Burkhard Endeward, Jörn Plackmeyer, Thomas F. Prisner","doi":"10.1016/j.jmr.2025.107886","DOIUrl":"10.1016/j.jmr.2025.107886","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"375 ","pages":"Article 107886"},"PeriodicalIF":2.0,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143887737","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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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

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

{"title":"Impact of non-polar solvents in dynamic nuclear polarization at high magnetic fields","authors":"Tomas Orlando , Huyen Bui , Jhersie Cabigting , Natalie Ibbetson , Johan van Tol , Thierry Dubroca , Xiaoling Wang , Frederic Mentink-Vigier","doi":"10.1016/j.jmr.2025.107885","DOIUrl":"10.1016/j.jmr.2025.107885","url":null,"abstract":"<div><div>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 (<sup>13</sup>C-CCl<sub>4</sub>/TEMPO and PPh<sub>3</sub>/BDPA) dispersed in CCl<sub>4</sub>, 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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"375 ","pages":"Article 107885"},"PeriodicalIF":2.0,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143887738","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

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

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

{"title":"Single and double-selective split-inversion pulse and recovery (SIP-R) sequences for targeted T1 relaxation measurements","authors":"Zachary G. Mayes, Yugandhara A.M. Eriyagama, Lingyu Chi, Thomas P. Schuman, Klaus Woelk","doi":"10.1016/j.jmr.2025.107884","DOIUrl":"10.1016/j.jmr.2025.107884","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"375 ","pages":"Article 107884"},"PeriodicalIF":2.0,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847904","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

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

Journal of magnetic resonance Pub Date : 2025-04-12 DOI: 10.1016/j.jmr.2025.107883

Nihar Pradeep Khandave , Ved Prakash Tiwari , Pramodh Vallurupalli

{"title":"Using the amide 15N CEST NMR experiment to study slow exchange between ‘visible’ protein states","authors":"Nihar Pradeep Khandave , Ved Prakash Tiwari , Pramodh Vallurupalli","doi":"10.1016/j.jmr.2025.107883","DOIUrl":"10.1016/j.jmr.2025.107883","url":null,"abstract":"<div><div>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 <sup>15</sup>N CEST experiment as an alternative to the <sup>1</sup>H<sup>N</sup>–<sup>15</sup>N ZZ exchange experiment to study exchange between ‘visible’ protein states. In the case of two-state exchange, the <sup>1</sup>H<sup>N</sup>–<sup>15</sup>N correlation map contains two correlations for each exchanging site, one arising from each state. Thus, two <sup>15</sup>N CEST profiles can be recorded for each of these sites using a single <sup>15</sup>N CEST experiment. We find that site-specific exchange parameters can then be obtained by simultaneously analysing both these <sup>15</sup>N CEST profiles recorded at a single ‘high’ <em>B</em><sub><em>1</em></sub> 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 <sup>15</sup>N 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<sup>−1</sup>) at 40 °C.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"375 ","pages":"Article 107883"},"PeriodicalIF":2.0,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143887739","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

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

Journal of magnetic resonance Pub Date : 2025-03-30 DOI: 10.1016/j.jmr.2025.107873

Ivan Argatov, Vitaly Kocherbitov

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

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2025-03-28 DOI: 10.1016/j.jmr.2025.107875

Ke Xu, Jörn Schmedt auf der Günne

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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

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

{"title":"Cryogenic field-cycling instrument for optical NMR hyperpolarization studies","authors":"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","doi":"10.1016/j.jmr.2025.107874","DOIUrl":"10.1016/j.jmr.2025.107874","url":null,"abstract":"<div><div>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 <em>T</em><sub>1</sub> 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 <sup>13</sup>C 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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"375 ","pages":"Article 107874"},"PeriodicalIF":2.0,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143814904","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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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

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

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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

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

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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

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

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