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Carbon-13 chemical shift tensor measurements for nitrogen-dense compounds 氮密集化合物的碳-13 化学位移张量测量。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-01-17 DOI: 10.1002/mrc.5422
Sean T. Holmes, Cameron M. Boley, Angelika Dewicki, Zachary T. Gardner, Cameron S. Vojvodin, Robbie J. Iuliucci, Robert W. Schurko

This paper reports the principal values of the 13C chemical shift tensors for five nitrogen-dense compounds (i.e., cytosine, uracil, imidazole, guanidine hydrochloride, and aminoguanidine hydrochloride). Although these are all fundamentally important compounds, the majority do not have 13C chemical shift tensors reported in the literature. The chemical shift tensors are obtained from 1H→13C cross-polarization magic-angle spinning (CP/MAS) experiments that were conducted at a high field of 18.8 T to suppress the effects of 14N-13C residual dipolar coupling. Quantum chemical calculations using density functional theory are used to obtain the 13C magnetic shielding tensors for these compounds. The best agreement with experiment arises from calculations using the hybrid functional PBE0 or the double-hybrid functional PBE0-DH, along with the triple-zeta basis sets TZ2P or pc-3, respectively, and intermolecular effects modeled using large clusters of molecules with electrostatic embedding through the COSMO approach. These measurements are part of an ongoing effort to expand the catalog of accurate 13C chemical shift tensor measurements, with the aim of creating a database that may be useful for benchmarking the accuracy of quantum chemical calculations, developing nuclear magnetic resonance (NMR) crystallography protocols, or aiding in applications involving machine learning or data mining. This work was conducted at the National High Magnetic Field Laboratory as part of a 2-week school for introducing undergraduate students to practical laboratory experience that will prepare them for scientific careers or postgraduate studies.

本文报告了五种氮密集化合物(即胞嘧啶、尿嘧啶、咪唑、盐酸胍和盐酸氨基胍)的 13 C 化学位移张量的主要值。虽然这些都是基本的重要化合物,但大多数都没有 13 C 化学位移张量的文献报道。化学位移张量是从 1 H→13 C 交叉偏振魔角旋转(CP/MAS)实验中获得的,这些实验是在 18.8 T 的高磁场下进行的,以抑制 14 N-13 C 残余偶极耦合的影响。利用密度泛函理论进行的量子化学计算获得了这些化合物的 13 C 磁屏蔽张量。通过使用混合函数 PBE0 或双混合函数 PBE0-DH,以及三重zeta 基集 TZ2P 或 pc-3 分别进行计算,并通过 COSMO 方法使用具有静电嵌入的大分子簇模拟分子间效应,得出了与实验最吻合的结果。这些测量结果是正在进行的扩大 13 C 化学位移张量精确测量目录工作的一部分,目的是建立一个数据库,用于为量子化学计算的准确性设定基准、开发核磁共振(NMR)晶体学协议或协助涉及机器学习或数据挖掘的应用。这项工作是在国家高磁场实验室进行的,是为期两周的学校活动的一部分,目的是向本科生介绍实验室实践经验,为他们将来从事科学工作或攻读研究生做好准备。
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引用次数: 0
Temperature lowering of liquid nitrogen via injection of helium gas bubbles improves the generation of parahydrogen-enriched gas 通过注入氦气泡降低液氮温度,可改善富含对氢的气体的生成。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-01-03 DOI: 10.1002/mrc.5423
James Daley, Joseph Siciliano, Vincent Ferraro, Elodie Sutter, Adam Lounsbery, Nicholas Whiting

The para spin isomer of hydrogen gas possesses high nuclear spin order that can enhance the NMR signals of a variety of molecular species. Hydrogen is routinely enriched in the para spin state by lowering the gas temperature while flowing through a catalyst. Although parahydrogen enrichments approaching 100% are achievable near the H2 liquefaction temperature of 20 K, many experimentalists operate at liquid nitrogen temperatures (77 K) due to the lower associated costs and overall simplicity of the parahydrogen generator. Parahydrogen that is generated at 77 K provides an enrichment value of ~51% of the para spin isomer; while useful, there are many applications that can benefit from low-cost access to higher parahydrogen enrichments. Here, we introduce a method of improving parahydrogen enrichment values using a liquid nitrogen-cooled generator that operates at temperatures less than 77 K. The boiling temperature of liquid nitrogen is lowered through internal evaporation into helium gas bubbles that are injected into the liquid. Changes to liquid nitrogen temperatures and parahydrogen enrichment values were monitored as a function of helium gas flow rate. The injected helium bubbles lowered the liquid nitrogen temperature to ~65.5 K, and parahydrogen enrichments of up to ~59% were achieved; this represents an ~16% improvement compared with the expected parahydrogen fraction at 77 K. This technique is simple to implement in standard liquid nitrogen-cooled parahydrogen generators and may be of interest to a wide range of scientists that require a cost-effective approach to improving parahydrogen enrichment values.

氢气的对位自旋异构体具有很高的核自旋阶次,可以增强各种分子物种的核磁共振信号。在氢气流经催化剂时,通过降低气体温度,可使氢气常规富集为对位自旋态。虽然在 20 K 的氢气液化温度附近可以实现接近 100% 的对位氢富集,但由于相关成本较低且对位氢发生器总体简单,许多实验人员在液氮温度(77 K)下进行操作。在 77 K 温度下生成的对氢提供了约 51% 的对位自旋异构体富集值;虽然有用,但许多应用可以从低成本获取更高的对氢富集值中获益。在此,我们介绍一种利用温度低于 77 K 的液氮冷却发生器提高对氢富集值的方法。液氮的沸腾温度通过内部蒸发进入注入液体的氦气泡而降低。液氮温度和对氢富集值的变化随氦气流速的变化而受到监测。注入的氦气泡将液氮温度降到了约 65.5 K,副氢富集度高达约 59%;与 77 K 时的预期副氢分数相比,提高了约 16%。这种技术在标准液氮冷却副氢发生器中实施起来非常简单,可能会引起需要以经济有效的方法提高副氢富集值的广大科学家的兴趣。
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引用次数: 0
A reliable external calibration method for reaction monitoring with benchtop NMR 用于台式核磁共振反应监测的可靠外部校准方法。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-12-20 DOI: 10.1002/mrc.5421
Tristan Maschmeyer, Breanna Conklin, Thomas C. Malig, David J. Russell, Kenji L. Kurita, Jason E. Hein, José G. Napolitano

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique with the ability to acquire both quantitative and structurally insightful data for multiple components in a test sample. This makes NMR spectroscopy a desirable tool to understand, monitor, and optimize chemical transformations. While quantitative NMR (qNMR) approaches relying on internal standards are well-established, using an absolute external calibration scheme is beneficial for reaction monitoring as resonance overlap complications from an added reference material to the sample can be avoided. Particularly, this type of qNMR technique is of interest with benchtop NMR spectrometers as the likelihood of resonance overlap is only enhanced with the lower magnetic field strengths of the used permanent magnets. The included study describes a simple yet robust methodology to determine concentration conversion factors for NMR systems using single- and multi-analyte linear regression models. This approach is leveraged to investigate a pharmaceutically relevant amide coupling batch reaction. An on-line stopped-flow (i.e., interrupted-flow or paused-flow) benchtop NMR system was used to monitor both the 1,1′-carbonyldiimidazole (CDI) promoted acid activation and the amide coupling. The results highlight how quantitative measurements in benchtop NMR systems can provide valuable information and enable analysts to make decisions in real time.

核磁共振(NMR)光谱是一种功能强大的分析技术,能够获取测试样品中多种成分的定量和结构数据。这使得核磁共振光谱成为了解、监控和优化化学转化的理想工具。虽然依赖于内部标准的定量 NMR(qNMR)方法已经非常成熟,但使用绝对外部校准方案有利于反应监测,因为可以避免样品中添加参考材料所产生的共振重叠并发症。这种 qNMR 技术尤其适用于台式 NMR 光谱仪,因为所使用的永磁体磁场强度较低,共振重叠的可能性就会增大。本研究介绍了一种简单而稳健的方法,利用单分析物和多分析物线性回归模型确定 NMR 系统的浓度转换系数。利用这种方法研究了与制药相关的酰胺偶联批量反应。在线停流(即间断流或暂停流)台式 NMR 系统用于监测 1,1'-羰基二咪唑 (CDI) 促进的酸活化和酰胺偶联。结果凸显了台式 NMR 系统的定量测量如何能够提供有价值的信息,并使分析人员能够实时做出决策。
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引用次数: 0
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 Q3 CHEMISTRY, MULTIDISCIPLINARY 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 Q3 CHEMISTRY, MULTIDISCIPLINARY 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 Q3 CHEMISTRY, MULTIDISCIPLINARY 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 Q3 CHEMISTRY, MULTIDISCIPLINARY 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 Q3 CHEMISTRY, MULTIDISCIPLINARY 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 Q3 CHEMISTRY, MULTIDISCIPLINARY 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 Q3 CHEMISTRY, MULTIDISCIPLINARY 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
期刊
Magnetic Resonance in Chemistry
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