Journal of magnetic resonance最新文献

{"title":"Operando electron spin probes for the study of battery processes","authors":"H. Nguyen,&nbsp;E.N. Bassey,&nbsp;E.E. Foley,&nbsp;D.A. Kitchaev,&nbsp;R. Giovine,&nbsp;R.J. Clément","doi":"10.1016/j.jmr.2024.107772","DOIUrl":"10.1016/j.jmr.2024.107772","url":null,"abstract":"<div><p><em>Operando</em> electron spin probes, namely magnetometry and electron paramagnetic resonance (EPR), provide real-time insights into the electrochemical processes occurring in battery materials and devices. In this work, we describe the design criteria and outline the development of <em>operando</em> magnetometry and EPR electrochemical cells. Notably, we show that a clamping mechanism, or springs, are needed to achieve sufficient compression of the battery stack and an electrochemical performance on par with that of a standard Swagelok-type cell. The tandem use of <em>operando</em> EPR and magnetometry allows us to identify five distinct and reversible redox processes taking place on charge and discharge of the intercalation-type LiNi_0.5Mn_0.5O₂ Li-ion cathode. While redox processes in conversion-type electrodes are notoriously difficult to investigate using standard characterization methods (e.g. X-ray based) and/or <em>post mortem</em> analysis, due to the formation of poorly crystalline and metastable reaction intermediates and products during cycling, we show that <em>operando</em> magnetometry provides unique insight into the kinetics and reversibility of Fe nanoparticle formation in the Na₃FeF₆ electrode for Na-based batteries. Step increases in the cell magnetization upon extended cycling indicate the build-up of Fe nanoparticles in the system, hinting at only partially reversible charge–discharge processes. The broad applicability of the tools developed herein to a range of electrode chemistries and structures, from intercalation to conversion electrodes, and from crystalline to amorphous systems, makes them particularly promising for the development of electrochemical energy storage technologies and beyond.</p></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107772"},"PeriodicalIF":2.0,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1090780724001563/pdfft?md5=9fe9fcb759db21e365298307ee6aa606&pid=1-s2.0-S1090780724001563-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recurrent neural network-aided processing of incomplete free induction decays in 1H-MRS of the brain","authors":"Eunho Jeong ,&nbsp;Joon Jang ,&nbsp;Ji-hoon Kim ,&nbsp;Hyeonjin Kim","doi":"10.1016/j.jmr.2024.107762","DOIUrl":"10.1016/j.jmr.2024.107762","url":null,"abstract":"<div><p>In the case of limited sampling windows or truncation of free induction decays (FIDs) for artifact removal in proton magnetic resonance spectroscopy (¹H‐MRS) and spectroscopic imaging (¹H‐MRSI), metabolite quantification needs to be performed on incomplete FIDs. Given that FIDs are naturally time-domain sequential data, we investigated the potential of recurrent neural network (RNN)-types of neural networks (NNs) in the processing of incomplete human brain FIDs with or without FID restoration prior to quantitative analysis at 3.0T.</p><p>First, we employed an RNN encoder-decoder and developed it to restore incomplete FIDs (rRNN) with different amounts of sampled data. The quantification of metabolites from the rRNN-restored FIDs was achieved by using LCModel. Second, we modified the RNN encoder-decoder and developed it to convert incomplete brain FIDs into incomplete metabolite-only FIDs without restoration, followed by linear regression using a metabolite basis set for quantitative analysis (cRNN). In consideration of the practical benefit of the FID restoration with respect to pure zero-filling, development and analysis of the NNs were focused particularly on the incomplete FIDs with only the first 64 data points retained. All NNs were trained on simulated data and tested mainly on in vivo data acquired from healthy volunteers (n = 27).</p><p>Strong correlations were obtained between the NN-derived and ground truth metabolite content (LCModel-derived content on fully sampled FIDs) for myo‐inositol, total choline, and total creatine (normalized to total N-acetylaspartate) on the in vivo data using both rRNN (R = 0.83–0.94; p ≤ 0.05) and cRNN (R = 0.86–0.91; p ≤ 0.05).</p><p>RNN-types of NNs have potential in the quantification of the major brain metabolites from the FIDs with substantially reduced sampled data points. For the metabolites with low to medium SNR, the performance of the NNs needs to be further improved, for which development of more elaborate and advanced simulation techniques would be of help, but remains challenging.</p></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107762"},"PeriodicalIF":2.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142238091","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 comparison of pulse and CW EPR T2-relaxation measurements of an inhomogeneously broadened nitroxide spin probe undergoing Heisenberg spin exchange 2. The intercept discrepancy","authors":"Barney L. Bales ,&nbsp;Miroslav Peric ,&nbsp;Robert N. Schwartz ,&nbsp;M.M. Bakirov ,&nbsp;I.T. Khairutdinov","doi":"10.1016/j.jmr.2024.107771","DOIUrl":"10.1016/j.jmr.2024.107771","url":null,"abstract":"<div><div>Experimental confirmation of a theoretical prediction of a non-linear broadening of the spin packets of nitroxide free radicals due to Heisenberg spin exchange at low concentrations, <span><math><mrow><mi>C</mi></mrow></math></span>, is presented. A recent demonstration that spectra with resolved proton hyperfine structure may be analyzed efficiently and accurately was utilized to confirm the theory. As <span><math><mrow><mi>C</mi><mo>→</mo><mn>0</mn></mrow></math></span>, a plot of the spin-packet line width (SPW) curves downward due to the presence of proton hyperfine couplings that increase the number of distinguishable quantum spin states. At higher <span><math><mrow><mi>C</mi></mrow></math></span>, the broadening is linear with <span><math><mrow><mi>C</mi></mrow></math></span> and the results for the spin exchange rate constant determined from the slope of the broadening of the average spin-packet line width and electron spin echo measurements are in agreement. It is shown that applying modest digital smoothing does not change the values of the SPW. An example of a practical application of these methods to published work is presented, allowing an enigma to be resolved.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107771"},"PeriodicalIF":2.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326693","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":"Restriction-induced time-dependent transcytolemmal water exchange: Revisiting the Kӓrger exchange model","authors":"Diwei Shi ,&nbsp;Fan Liu ,&nbsp;Sisi Li ,&nbsp;Li Chen ,&nbsp;Xiaoyu Jiang ,&nbsp;John C. Gore ,&nbsp;Quanshui Zheng ,&nbsp;Hua Guo ,&nbsp;Junzhong Xu","doi":"10.1016/j.jmr.2024.107760","DOIUrl":"10.1016/j.jmr.2024.107760","url":null,"abstract":"<div><p>The Kӓrger model and its derivatives have been widely used to incorporate transcytolemmal water exchange rate, an essential characteristic of living cells, into analyses of diffusion MRI (dMRI) signals from tissues. The Kӓrger model consists of two homogeneous exchanging components coupled by an exchange rate constant and assumes measurements are made with sufficiently long diffusion time and slow water exchange. Despite successful applications, it remains unclear whether these assumptions are generally valid for practical dMRI sequences and biological tissues. In particular, barrier-induced restrictions to diffusion produce inhomogeneous magnetization distributions in relatively large-sized compartments such as cancer cells, violating the above assumptions. The effects of this inhomogeneity are usually overlooked. We performed computer simulations to quantify how restriction effects, which in images produce edge enhancements at compartment boundaries, influence different variants of the Kӓrger-model. The results show that the edge enhancement effect will produce larger, time-dependent estimates of exchange rates in e.g., tumors with relatively large cell sizes (&gt;10 μm), resulting in overestimations of water exchange as previously reported. Moreover, stronger diffusion gradients, longer diffusion gradient durations, and larger cell sizes, all cause more pronounced edge enhancement effects. This helps us to better understand the feasibility of the Kärger model in estimating water exchange in different tissue types and provides useful guidance on signal acquisition methods that may mitigate the edge enhancement effect. This work also indicates the need to correct the overestimated transcytolemmal water exchange rates obtained assuming the Kärger-model.</p></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"367 ","pages":"Article 107760"},"PeriodicalIF":2.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1090780724001447/pdfft?md5=f8473d8afcad5e5d4a4d7cea3da4a920&pid=1-s2.0-S1090780724001447-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142147208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The NOAH HSQC-COSY module revisited: A theoretical and practical comparison of pulse sequences","authors":"Jonathan R.J. Yong ,&nbsp;Ēriks Kupče ,&nbsp;Tim D.W. Claridge","doi":"10.1016/j.jmr.2024.107759","DOIUrl":"10.1016/j.jmr.2024.107759","url":null,"abstract":"<div><p>NMR supersequences, as exemplified by the NOAH (NMR by Ordered Acquisition using ¹H detection) technique, are a powerful way of acquiring multiple 2D data sets in much shorter durations. This is accomplished through targeted excitation and detection of the magnetisation belonging to specific isotopologues (‘magnetisation pools’). Separately, the HSQC-COSY experiment has recently seen an increase in popularity due to the high signal dispersion in the indirect dimension and the removal of ambiguity traditionally associated with HSQC-TOCSY experiments. Here, we describe how the HSQC-COSY experiment can be integrated as a ‘module’ within NOAH supersequences. The benefits and drawbacks of several different pulse sequence implementations are discussed, with a particular focus on how sensitivities of other modules in the same supersequence are affected.</p></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"367 ","pages":"Article 107759"},"PeriodicalIF":2.0,"publicationDate":"2024-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1090780724001435/pdfft?md5=67f79ba4d83ba494e82823eaf06fb5d5&pid=1-s2.0-S1090780724001435-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142095148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Towards shorter composite 180° refocusing pulses for NMR","authors":"Stephen Wimperis","doi":"10.1016/j.jmr.2024.107758","DOIUrl":"10.1016/j.jmr.2024.107758","url":null,"abstract":"<div><p>Novel composite 180° pulses are designed for use in nuclear magnetic resonance (NMR) and verified experimentally using solution-state ¹H NMR spectroscopy. Rather than being constructed from 180° pulses (as in much recent work), the new composite pulses are constructed from 90° pulses, with the aim of finding sequences that are shorter overall than existing equivalents. The primary (but not exclusive) focus is on composite pulses that are dual compensated – simultaneously broadband with respect to both inhomogeneity of the radiofrequency field and resonance offset – and have antisymmetric phase schemes, such that they can be used to form spin echoes without the introduction of a phase error. In particular, a new antisymmetric dual-compensated refocusing pulse is presented that is constructed from ten 90° pulses, equivalent to just five 180° pulses.</p></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"367 ","pages":"Article 107758"},"PeriodicalIF":2.0,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1090780724001423/pdfft?md5=759c2933286a1c53d0fc75bfcb2a382b&pid=1-s2.0-S1090780724001423-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142161731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Diffusion Exchange Ratio (DEXR): A minimal sampling of diffusion exchange spectroscopy to probe exchange, restriction, and time-dependence","authors":"Teddy X. Cai ,&nbsp;Nathan H. Williamson ,&nbsp;Rea Ravin ,&nbsp;Peter J. Basser","doi":"10.1016/j.jmr.2024.107745","DOIUrl":"10.1016/j.jmr.2024.107745","url":null,"abstract":"&lt;div&gt;&lt;p&gt;Water exchange is increasingly recognized as an important biological process that can affect the study of biological tissue using diffusion MR. Methods to measure exchange, however, remain immature as opposed to those used to characterize restriction, with no consensus on the optimal pulse sequence (s) or signal model (s). In general, the trend has been towards data-intensive fitting of highly parameterized models. We take the opposite approach and show that a judicious sub-sample of diffusion exchange spectroscopy (DEXSY) data can be used to robustly quantify exchange, as well as restriction, in a data-efficient manner. This sampling produces a ratio of two points per mixing time: (i) one point with equal diffusion weighting in both encoding periods, which gives maximal exchange contrast, and (ii) one point with the same &lt;em&gt;total&lt;/em&gt; diffusion weighting in just the first encoding period, for normalization. We call this quotient the Diffusion EXchange Ratio (DEXR). Furthermore, we show that it can be used to probe time-dependent diffusion by estimating the velocity autocorrelation function (VACF) over intermediate to long times (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;500&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;ms&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). We provide a comprehensive theoretical framework for the design of DEXR experiments in the case of static or constant gradients. Data from Monte Carlo simulations and experiments acquired in fixed and viable &lt;em&gt;ex vivo&lt;/em&gt; neonatal mouse spinal cord using a permanent magnet system are presented to test and validate this approach. In viable spinal cord, we report the following apparent parameters from just 6 data points: &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;k&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;17&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;ms&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;72&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;01&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;eff&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;05&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;01&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;μm&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;κ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;eff&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;19&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;04&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;μm/ms&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, which correspond to the exchange time, restricted or non-Gaussian signal fraction, an effective spherical radius, and permeability, respectively. For the VACF, we report a long-time, power-law scaling with &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;≈&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;t&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, which is approximately consistent with disordered domains in 3-D. Overall, the DEXR method is shown to be highly efficient, capable of providing valuable quantitative ","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"366 ","pages":"Article 107745"},"PeriodicalIF":2.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141914952","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 complete 3D-printed tool kit for Solid-State NMR sample and rotor handling","authors":"Martin A. Olson ,&nbsp;Ruixian Han ,&nbsp;Thirupathi Ravula ,&nbsp;Collin G. Borcik ,&nbsp;Songlin Wang ,&nbsp;Perla A. Viera ,&nbsp;Chad M. Rienstra","doi":"10.1016/j.jmr.2024.107748","DOIUrl":"10.1016/j.jmr.2024.107748","url":null,"abstract":"<div><p>Solid state NMR (SSNMR) is a highly versatile and broadly applicable method for studying the structure and dynamics of biomolecules and materials. For scientists entering the field of SSNMR, the many quotidian activities required in the workflow to prepare samples for data collection can present a significant barrier to adoption. These steps include transfer of samples into rotors, marking the reflective surfaces for high sensitivity tachometer signal detection, inserting rotors into the magic-angle spinning (MAS) stator, achieving stable spinning, and removing and storing rotors to ensure reproducibility of data collection conditions. Even experienced spectroscopists experience occasional problems with these operations, and the cumulative probability of a delay to successful data collection is high enough to cause frequent disruptions to instrument schedules, particularly in the context of large facilities serving a diverse community of users. These problems are all amplified when utilizing rotors smaller than about 4 mm in diameter. Therefore, to improve the reliability and robustness of SSNMR sample preparation workflows, here we describe a set of tools for rotor packing, unpacking, tachometer marking, extraction and storage. Stereolithography 3D printing was employed as a cost-effective and convenient method for prototyping and manufacturing a full range of designs suitable for several types of probes and rotor geometries.</p></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"366 ","pages":"Article 107748"},"PeriodicalIF":2.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142044405","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":"Tetrakis(trimethylsilyl)silane as a standard compound for fast spinning Solid-State NMR experiments","authors":"Ruixian Han ,&nbsp;Alexander L. Paterson ,&nbsp;Moses H. Milchberg ,&nbsp;Yuanchi Pang ,&nbsp;Boden H. Vanderloop ,&nbsp;Chad M. Rienstra","doi":"10.1016/j.jmr.2024.107747","DOIUrl":"10.1016/j.jmr.2024.107747","url":null,"abstract":"<div><p>The development of magic angle spinning (MAS) at rates ranging from 30 kHz to greater than 100 kHz has substantially advanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy ¹H-detection methods. The small rotors required for such MAS rates have a limited sample volume and low ¹³C-detection sensitivity, rendering the traditional set of standard compounds for SSNMR insufficient or highly inconvenient for shimming and magic-angle calibration. Additionally, the reproducibility of magic angle setting, chemical shift referencing, and probe position can be especially critical for SSNMR experiments at high fields. These conditions suggest the need for a high signal-to-noise ratio (SNR) ¹H-detection standard compound, which is preferably multi-purpose, to simplify instrument set up for ultra-fast MAS SSNMR instruments at high magnetic fields. In this study, we present the results for setting magic angle and shimming using tetrakis(trimethylsilyl)silane (TTMSS, or TKS), a tetramethylsilane (TMS) analogue, at near 40 kHz and demonstrate that we can achieve favorable results in less time but with equal or superior precision as traditional KBr and adamantane standards. The high SNR and TMS-like chemical shift of TKS also opens the possibilities for using TKS as an internal standard with biological samples. A single rotor containing a four-component mixture of TKS, adamantane, uniformly ¹³C, ¹⁵N-labeled N-acetyl valine and KBr was used to perform a complete configuration and calibration of a SSNMR probe without sample changes. We anticipate TKS as a standard compound to be especially effective at very high MAS conditions and to greatly simplify the instrument set up for high and ultra-high field SSNMR instruments.</p></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"367 ","pages":"Article 107747"},"PeriodicalIF":2.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142047727","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":"Super-resolution NMR spectroscopy","authors":"Luca Wenchel ,&nbsp;Olivia Gampp ,&nbsp;Roland Riek","doi":"10.1016/j.jmr.2024.107746","DOIUrl":"10.1016/j.jmr.2024.107746","url":null,"abstract":"<div><p>Spectral resolution is one of the limiting factors in nuclear magnetic resonance (NMR) spectroscopy of biological systems where signal overlap often interferes with chemical shift assignment as well as dynamics and structure analysis. This problem can be addressed in part by using higher magnetic field NMR spectrometers operating at up to 1.2 GHz ¹H frequency to enhance the resolution proportionally with the field strength, and by deuteration in combination with transverse relaxation-optimized spectroscopy that reduces the transverse relaxation rate and proportionally the resonance linewidth of the peaks yielding higher spectral resolution. As a complement or alternative to these expensive and often insufficient approaches, we present here a generally applicable method to reduce the linewidth of peaks in indirect dimensions of multi-dimensional NMR spectra by increasing the number of scans per time increment exponentially as a function of time in order to compensate, in part, the decay of the signal caused by transverse relaxation. This enables to achieve a user-defined linewidth of the peaks without undue increase of the noise. Optimization by including in the number of scans also a cosine apodization function as well as processing spectra with an exponential-cosine window function in the direct dimension results typically in a resolution enhancement (linewidth reduction) by a factor of 1.5–2 in comparison to a standard measurement with a constant number of scans per time increment. This is comparable to the 2-fold resolution enhancement that can be obtained by going from a 600 MHz ¹H frequency NMR spectrometer to a 1.2 GHz instrument, or from 1.2 GHz to a spectrum measured hypothetically at 2.4 GHz ¹H frequency. A factor of two resolution enhancement causes thereby a signal to noise loss of a factor of three. The sensitivity gain by dynamic number of scan sampling is thereby ∼20 % over the use of a digital apodization function.</p></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"366 ","pages":"Article 107746"},"PeriodicalIF":2.0,"publicationDate":"2024-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1090780724001307/pdfft?md5=a4a8c026a704df7c0d6034901bc7234d&pid=1-s2.0-S1090780724001307-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141997492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}