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Twenty years of nmrshiftdb2: A case study of an open database for analytical chemistry nmrshiftdb2二十年:分析化学开放数据库案例研究。
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-12-19 DOI: 10.1002/mrc.5418
Stefan Kuhn, Heinz Kolshorn, Christoph Steinbeck, Nils Schlörer

In October 2003, 20 years ago, the open-source and open-content database NMRshiftDB was announced. Since then, the database, renamed as nmrshiftdb2 later, has been continuously available and is one of the longer-running projects in the field of open data in chemistry. After 20 years, we evaluate the success of the project and present lessons learnt for similar projects.

20 年前的 2003 年 10 月,开源和开放内容数据库 NMRshiftDB 发布。从那时起,该数据库(后更名为 nmrshiftdb2)一直持续可用,是化学开放数据领域运行时间较长的项目之一。20 年后,我们对该项目的成功进行了评估,并介绍了类似项目的经验教训。
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引用次数: 0
Predicting 51V nuclear magnetic resonance observables in molecular crystals 预测分子晶体中的 51 V 核磁共振观测值。
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-12-19 DOI: 10.1002/mrc.5420
Joshua D. Hartman, Daniel Capistran

Solid-state nuclear magnetic resonance (NMR) spectroscopy and quantum chemical density functional theory (DFT) calculations are widely used to characterize vanadium centers in biological and pharmaceutically relevant compounds. Several techniques have been recently developed to improve the accuracy of predicted NMR parameters obtained from DFT. Fragment-based and planewave-corrected methods employing hybrid density functionals are particularly effective tools for solid-state applications. A recent benchmark study involving molecular crystal compounds found that fragment-based NMR calculations using hybrid density functionals improve the accuracy of predicted 51V chemical shieldings by 20% relative to traditional planewave methods. This work extends the previous study, including a careful analysis of 51V chemical shift anisotropy, electric field gradient calculations, and a more extensive test set. The accuracy of planewave-corrected techniques and recently developed fragment-based methods using electrostatic embedding based on the polarized continuum model (PCM) are found to be highly competitive with previous methods. Planewave-corrected methods achieve a 34% improvement in the errors of predicted 51V chemical shieldings relative to planewave. Additionally, planewave-corrected and fragment-based calculations were performed using PCM embedding, improving the accuracy of predicted 51V chemical shielding (CS) tensor principal values by 30% and Cq values by 15% relative to traditional planewave methods. The performance of these methods is further examined using a redox-active oxovandium complex and a common 51V NMR reference compound.

固态核磁共振(NMR)光谱和量子化学密度泛函理论(DFT)计算被广泛用于表征生物和制药相关化合物中的钒中心。最近开发了几种技术,以提高从 DFT 中获得的 NMR 参数预测的准确性。采用混合密度函数的基于片段和平面波校正的方法是固态应用中特别有效的工具。最近一项涉及分子晶体化合物的基准研究发现,与传统的平面波方法相比,采用混合密度函数的基于片段的 NMR 计算可将 51 V 化学屏蔽的预测精度提高 20%。这项工作扩展了之前的研究,包括对 51 V 化学位移各向异性的仔细分析、电场梯度计算和更广泛的测试集。结果发现,平面波校正技术和最近开发的基于极化连续体模型(PCM)的静电嵌入片段法的准确性与以前的方法相比具有很强的竞争力。相对于平面波,平面波校正方法将 51 V 化学屏蔽的预测误差提高了 34%。此外,使用 PCM 嵌入进行了平面波校正和基于片段的计算,与传统的平面波方法相比,51 V 化学屏蔽 (CS) 张量主值的预测精度提高了 30%,C q $$ {C}_q $$ 值的预测精度提高了 15%。使用氧化还原活性氧钒复合物和常见的 51 V NMR 参考化合物进一步检验了这些方法的性能。
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引用次数: 0
Polarization transfer methods for quantitative analysis of flowing mixtures with benchtop 13C NMR spectroscopy 利用台式 13 C NMR 光谱定量分析流动混合物的极化转移方法。
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-12-19 DOI: 10.1002/mrc.5417
Johnnie Phuong, Zeno Romero, Hans Hasse, Kerstin Münnemann

Benchtop NMR spectroscopy is attractive for process monitoring; however, there are still drawbacks that often hamper its use, namely, the comparatively low spectral resolution in 1H NMR, as well as the low signal intensities and problems with the premagnetization of flowing samples in 13C NMR. We show here that all these problems can be overcome by using 1H-13C polarization transfer methods. Two ternary test mixtures (one with overlapping peaks in the 1H NMR spectrum and one with well-separated peaks, which was used as a reference) were studied with a 1 T benchtop NMR spectrometer using the polarization transfer sequence PENDANT (polarization enhancement that is nurtured during attached nucleus testing). The mixtures were analyzed quantitatively in stationary as well as in flow experiments by PENDANT enhanced 13C NMR experiments, and the results were compared with those from the gravimetric sample preparation and from standard 1H and 13C NMR spectroscopy. Furthermore, as a proxy for a process monitoring application, continuous dilution experiments were carried out, and the composition of the mixture was monitored in a flow setup by 13C NMR benchtop spectroscopy with PENDANT. The results demonstrate the high potential of polarization transfer methods for applications in quantitative process analysis with benchtop NMR instruments, in particular with flowing samples.

台式 NMR 光谱法对过程监控很有吸引力;但仍有一些缺点经常妨碍其使用,即 1 H NMR 的光谱分辨率相对较低,13 C NMR 的信号强度较低以及流动样品的预磁化问题。我们在此表明,使用 1 H-13 C 极化转移方法可以克服所有这些问题。我们在 1 T 台式 NMR 光谱仪上使用偏振转移序列 PENDANT(在附核测试过程中培育的偏振增强)对两种三元测试混合物(一种在 1 H NMR 光谱中具有重叠峰,另一种具有分离良好的峰,用作参照物)进行了研究。通过 PENDANT 增强 13 C NMR 实验对固定和流动实验中的混合物进行了定量分析,并将结果与重力样品制备以及标准 1 H 和 13 C NMR 光谱分析的结果进行了比较。此外,作为过程监测应用的代表,还进行了连续稀释实验,并在流动设置中使用 PENDANT 的 13 C NMR 台式光谱仪监测混合物的成分。结果表明,极化转移方法在台式 NMR 仪器的定量过程分析(尤其是流动样品)中具有巨大的应用潜力。
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引用次数: 0
Intracellular pyruvate–lactate–alanine cycling detected using real-time nuclear magnetic resonance spectroscopy of live cells and isolated mitochondria 利用活细胞和分离线粒体的实时核磁共振光谱检测细胞内丙酮酸-乳酸-丙氨酸循环
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-12-14 DOI: 10.1002/mrc.5419
G. A. Nagana Gowda, John A. Lusk, Vadim Pascua

Pyruvate, an end product of glycolysis, is a master fuel for cellular energy. A portion of cytosolic pyruvate is transported into mitochondria, while the remaining portion is converted reversibly into lactate and alanine. It is suggested that cytosolic lactate and alanine are transported and metabolized inside mitochondria. However, such a mechanism continues to be a topic of intense debate and investigation. As a part of gaining insight into the metabolic fate of the cytosolic lactate and alanine; in this study, the metabolism of mouse skeletal myoblast cells (C2C12) and their isolated mitochondria was probed utilizing stable isotope-labeled forms of the three glycolysis products, viz. [3-13C1]pyruvate, [3-13C1]lactate, and [3-13C1]alanine, as substrates. The uptake and metabolism of each substrate was monitored, separately, in real-time using 1H-13C 2D nuclear magnetic resonance (NMR) spectroscopy. The dynamic variation of the levels of the substrates and their metabolic products were quantitated as a function of time. The results demonstrate that all three substrates were transported into mitochondria, and each substrate was metabolized to form the other two metabolites, reversibly. These results provide direct evidence for intracellular pyruvate–lactate–alanine cycling, in which lactate and alanine produced by the cytosolic pyruvate are transported into mitochondria and converted back to pyruvate. Such a mechanism suggests a role for lactate and alanine to replenish mitochondrial pyruvate, the primary source for adenosine triphosphate (ATP) synthesis through oxidative phosphorylation and the electron transport chain. The results highlight the potential of real-time NMR spectroscopy for gaining new insights into cellular and subcellular functions.

丙酮酸是糖酵解的最终产物,是细胞能量的主要燃料。细胞膜丙酮酸的一部分被转运到线粒体,而剩余部分则可逆地转化为乳酸和丙氨酸。有人认为,细胞质乳酸和丙氨酸在线粒体内被运输和代谢。然而,这种机制仍然是一个激烈争论和研究的话题。为了深入了解细胞膜乳酸和丙氨酸的代谢去向,本研究利用稳定同位素标记的三种糖酵解产物(即[3-13C1]丙酮酸、[3-13C1]乳酸和[3-13C1]丙氨酸)作为底物,对小鼠骨骼肌母细胞(C2C12)及其分离的线粒体的代谢进行了探究。利用 1H-13C 二维核磁共振(NMR)光谱分别实时监测了每种底物的摄取和代谢。底物及其代谢产物水平的动态变化随时间的变化而量化。结果表明,所有三种底物都被转运到线粒体中,并且每种底物都被可逆地代谢成另外两种代谢产物。这些结果提供了细胞内丙酮酸-乳酸-丙氨酸循环的直接证据,在这种循环中,细胞内丙酮酸产生的乳酸和丙氨酸被转运到线粒体,并转化回丙酮酸。这种机制表明乳酸和丙氨酸在补充线粒体丙酮酸方面发挥作用,而线粒体丙酮酸是通过氧化磷酸化和电子传递链合成三磷酸腺苷(ATP)的主要来源。这些结果凸显了实时核磁共振光谱在获得细胞和亚细胞功能新见解方面的潜力。
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引用次数: 0
PDSFit: PDS data analysis in the presence of orientation selectivity, g-anisotropy, and exchange coupling PDSFit:存在取向选择性、g-各向异性和交换耦合时的 PDS 数据分析
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-12-12 DOI: 10.1002/mrc.5415
Dinar Abdullin, Pablo Rauh Corro, Tobias Hett, Olav Schiemann

Pulsed dipolar electron paramagnetic resonance spectroscopy (PDS), encompassing techniques such as pulsed electron–electron double resonance (PELDOR or DEER) and relaxation-induced dipolar modulation enhancement (RIDME), is a valuable method in structural biology and materials science for obtaining nanometer-scale distance distributions between electron spin centers. An important aspect of PDS is the extraction of distance distributions from the measured time traces. Most software used for this PDS data analysis relies on simplifying assumptions, such as assuming isotropic g-factors of ~2 and neglecting orientation selectivity and exchange coupling. Here, the program PDSFit is introduced, which enables the analysis of PELDOR and RIDME time traces with or without orientation selectivity. It can be applied to spin systems consisting of up to two spin centers with anisotropic g-factors and to spin systems with exchange coupling. It employs a model-based fitting of the time traces using parametrized distance and angular distributions, and parametrized PDS background functions. The fitting procedure is followed by an error analysis for the optimized parameters of the distributions and backgrounds. Using five different experimental data sets published previously, the performance of PDSFit is tested and found to provide reliable solutions.

脉冲双极性电子顺磁共振波谱(PDS)包括脉冲电子-电子双共振(PELDOR 或 DEER)和弛豫诱导双极性调制增强(RIDME)等技术,是结构生物学和材料科学领域获取电子自旋中心之间纳米级距离分布的重要方法。PDS 的一个重要方面是从测量的时间轨迹中提取距离分布。大多数用于 PDS 数据分析的软件都依赖于简化假设,例如假设各向同性的 g 因子为 ~2 并忽略取向选择性和交换耦合。这里介绍的是 PDSFit 程序,它可以分析具有或不具有取向选择性的 PELDOR 和 RIDME 时间轨迹。该程序可应用于最多由两个具有各向异性 g 因子的自旋中心组成的自旋系统以及具有交换耦合的自旋系统。它使用参数化的距离和角度分布以及参数化的 PDS 背景函数对时间轨迹进行基于模型的拟合。拟合过程之后,对分布和背景的优化参数进行误差分析。利用之前发布的五个不同的实验数据集,对 PDSFit 的性能进行了测试,发现它能提供可靠的解决方案。
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引用次数: 0
Determination of self-diffusion coefficients in mixtures with benchtop 13C NMR spectroscopy via polarization transfer 偏振转移台式13c核磁共振光谱法测定混合物自扩散系数。
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-11-28 DOI: 10.1002/mrc.5412
Johnnie Phuong, Sarah Mross, Daniel Bellaire, Hans Hasse, Kerstin Münnemann

Nuclear magnetic resonance (NMR) is an established method to determine self-diffusion coefficients in liquids with high precision. The development of benchtop NMR spectrometers makes the method accessible to a wider community. In most cases, 1H NMR spectroscopy is used to determine self-diffusion coefficients due to its high sensitivity. However, especially when using benchtop NMR spectrometers for the investigation of complex mixtures, the signals in 1H NMR spectra can overlap, hindering the precise determination of self-diffusion coefficients. In 13C NMR spectroscopy, the signals of different compounds are generally well resolved. However, the sensitivity of 13C NMR is significantly lower than that of 1H NMR spectroscopy leading to very long measurement times, which makes diffusion coefficient measurements based on 13C NMR practically infeasible with benchtop NMR spectrometers. To circumvent this problem, we have combined two known pulse sequences, one for polarization transfer from 1H to the 13C nuclei (PENDANT) and one for the measurement of diffusion coefficients (PFG). The new method (PENPFG) was used to measure the self-diffusion coefficients of three pure solvents (acetonitrile, ethanol and 1-propanol) as well as in all their binary mixtures and the ternary mixture at various compositions. For comparison, also measurements of the same systems were carried out with a standard PFG-NMR routine on a high-field NMR instrument. The results are in good agreement and show that PENPFG is a useful tool for the measurement of the absolute value of the self-diffusion coefficients in complex liquid mixtures with benchtop NMR spectrometers.

核磁共振(NMR)是一种成熟的高精度测定液体自扩散系数的方法。台式核磁共振光谱仪的发展使该方法可被更广泛的社区使用。在大多数情况下,由于其高灵敏度,采用1h核磁共振谱法来确定自扩散系数。然而,特别是在使用台式核磁共振光谱仪研究复杂混合物时,1 H核磁共振光谱中的信号可能重叠,阻碍了自扩散系数的精确测定。在13c核磁共振光谱中,不同化合物的信号通常被很好地分解。然而,13c核磁共振的灵敏度明显低于1h核磁共振光谱,导致测量时间很长,这使得基于13c核磁共振的扩散系数测量在台式核磁共振光谱仪上实际上是不可实现的。为了解决这个问题,我们结合了两个已知的脉冲序列,一个用于从1h到13c核的极化转移(PENDANT),另一个用于扩散系数的测量(PFG)。采用新方法(PENPFG)测定了三种纯溶剂(乙腈、乙醇和1-丙醇)及其所有二元混合物和不同组成的三元混合物的自扩散系数。为了进行比较,在高场核磁共振仪上使用标准PFG-NMR程序进行了相同系统的测量。结果吻合良好,表明PENPFG是用台式核磁共振光谱仪测量复杂液体混合物中自扩散系数绝对值的有用工具。
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引用次数: 0
Non-uniform sampling to enhance the performance of compact NMR for characterizing new psychoactive substances 非均匀取样,以提高紧凑核磁共振表征新的精神活性物质的性能。
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-11-23 DOI: 10.1002/mrc.5416
Thomas Castaing-Cordier, Sélina Crasnier, Damien Dubois, Virginie Ladroue, Audrey Buleté, Cédric Prudhomme, Céline Charvoz, Fabrice Besacier, Denis Jacquemin, Patrick Giraudeau, Jonathan Farjon

Efficient and robust analytical methods are needed to improve the identification and subsequent regulation of new psychoactive substances (NPS). NMR spectroscopy is a unique method able to determine the structure of small molecules such as NPS even in mixtures. However, high-field NMR analysis is associated with expensive purchase and maintenance costs. For more than a decade, compact NMR spectrometers have changed this paradigm. It was recently shown that a dedicated analytical workflow combining compact NMR and databases could identify the molecular structure of NPS, in spite of the lower spectral dispersion and sensitivity of compact spectrometers. This approach relies on 1H-13C HSQC to both recognize NPS and elucidate the structure of unknown substances. Still, its performance is limited by the need to compromise between resolution and experiment time. Here, we show that this strategy can be significantly improved by implementing non-uniform sampling (NUS) to improve spectral resolution in the 13C dimension of HSQC at no cost in terms of experiment time. Gains in the range of 3 to 4 in resolution are achieved for pure NPS and for a mixture. Finally, 2D HSQC with NUS was applied to improve the identification of NPS with the assistance of databases. The resulting method appears as a useful tool for the characterization of NPS in mixtures, which is essential for forensic laboratories.

需要有效和稳健的分析方法来改进新精神活性物质(NPS)的识别和后续监管。核磁共振波谱是一种独特的方法,能够确定小分子的结构,如NPS,甚至在混合物中。然而,高场核磁共振分析与昂贵的购买和维护成本相关。十多年来,紧凑型核磁共振光谱仪改变了这种模式。最近的研究表明,结合紧凑核磁共振和数据库的专用分析工作流程可以识别NPS的分子结构,尽管紧凑光谱仪的光谱色散和灵敏度较低。该方法依靠1 H-13 C HSQC来识别NPS和阐明未知物质的结构。然而,由于需要在分辨率和实验时间之间折衷,它的性能受到限制。在这里,我们表明,通过实施非均匀采样(NUS)可以显著改进该策略,以提高HSQC在13 C维度的光谱分辨率,而不需要花费实验时间。对于纯NPS和混合物,分辨率增益在3到4之间。最后,利用基于NUS的二维HSQC技术,在数据库的辅助下提高对NPS的识别。由此产生的方法似乎是表征混合物中NPS的有用工具,这对法医实验室至关重要。
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引用次数: 0
To flame-seal or not to flame-seal NMR tubes: The role of liquid–vapor equilibria on the accuracy of variable temperature experiments 采用火焰密封或不采用火焰密封核磁共振管:汽液平衡对变温实验精度的影响。
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-11-22 DOI: 10.1002/mrc.5411
Derek Morrelli, Santanu Maitra, V. V. Krishnan

In NMR experiments, it is crucial to control the temperature of the sample, especially when measuring kinetic parameters. Usually, it takes 2 to 5 min for the temperature of the sample inside the NMR probe to stabilize at a fixed value set for the experiment. However, the NMR sample tubes are flame-sealed in some cases, such as when working with volatile solvents, atmosphere-sensitive samples, or calibration samples for long-term use. When these samples are placed inside the NMR probe, the spectrometer controls the lower portion (liquid phase) of the NMR sample tube with a gas flow at a fixed temperature, while the upper portion (vapor) is at ambient temperature. This probe design creates a unique temperature gradient across the sample, leading to vapor pressure build-up, particularly inside a sealed NMR tube. By analyzing the temperature-dependent spectral line shape changes of a chemical exchange process, we report that under standard experimental conditions, the sample temperature can take up to 2 to 3 h (instead of minutes) to stabilize. The time scale of the liquid–vapor equilibrium process is much slower, with a half-life exceeding 35 min, in contrast to the 2-min duration required to obtain each spectrum. This phenomenon is exclusively due to the liquid–vapor equilibrium process of the flame-sealed NMR tube and is not observable otherwise.

在核磁共振实验中,控制样品的温度是至关重要的,特别是在测量动力学参数时。通常情况下,样品在核磁共振探头内的温度需要2 ~ 5min才能稳定在实验设定的固定值。然而,在某些情况下,核磁共振样管是火焰密封的,例如当使用挥发性溶剂,大气敏感样品或长期使用的校准样品时。当这些样品被放置在核磁共振探针内时,光谱仪控制核磁共振样品管的下部(液相)在固定温度下以气体流动,而上部(蒸汽)在环境温度下。这种探针设计在样品上产生独特的温度梯度,导致蒸汽压力积聚,特别是在密封的核磁共振管内。通过分析化学交换过程的温度依赖谱线形状变化,我们报告说,在标准实验条件下,样品温度可能需要2到3小时(而不是几分钟)才能稳定。液-气平衡过程的时间尺度要慢得多,半衰期超过35分钟,而获得每个光谱所需的时间为2分钟。这种现象完全是由于火焰密封核磁共振管的液-气平衡过程引起的,否则无法观察到。
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引用次数: 0
Frontiers in NMR metabolomics 核磁共振代谢组学前沿。
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-11-21 DOI: 10.1002/mrc.5400
G. A. Nagana Gowda, Robert Powers
{"title":"Frontiers in NMR metabolomics","authors":"G. A. Nagana Gowda,&nbsp;Robert Powers","doi":"10.1002/mrc.5400","DOIUrl":"10.1002/mrc.5400","url":null,"abstract":"","PeriodicalId":18142,"journal":{"name":"Magnetic Resonance in Chemistry","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2023-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138176531","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
13C-depleted algae as food: Permitting background free in-vivo nuclear magnetic resonance of Daphnia magna at natural abundance 作为食物的贫碳藻类:允许大水蚤在自然丰度下的无背景核磁共振。
IF 2 3区 化学 Q2 Chemistry Pub Date : 2023-11-20 DOI: 10.1002/mrc.5409
William W. Wolff, Jacob Pellizzari, Ronald Soong, Daniel H. Lysak, Katrina Steiner, Kiera Ronda, Peter Costa, Katelyn Downey, Vincent Moxley-Paquette, Chris Suszczynski, Steven Boehmer, Jacob R. Prat, Andre J. Simpson

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引用次数: 0
期刊
Magnetic Resonance in Chemistry
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