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Simulation of oriented NMR spectra: Combining molecular dynamics and chemical shift tensor calculations 定向NMR光谱的模拟:结合分子动力学和化学位移张量计算。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-10-26 DOI: 10.1002/mrc.5403
Ulrich Sternberg, Raiker Witter

Solid state NMR is widely used to study the orientation and other structural features of proteins and peptides in lipid bilayers. Using data obtained by PISEMA (Polarization Inversion Spin Exchange at Magic Angle) experiments, periodic spectral patterns arise from well-aligned α-helical molecules. Significant problems in the interpretation of PISEMA spectra may arise for systems that do not form perfectly defined secondary structures, like α-helices, or the signal pattern is disturbed by molecular motion. Here, we present a new method that combines molecular dynamics simulation with tensorial orientational constraints (MDOC) and chemical shift tensor calculations for the simulation and interpretation of PISEMA-like spectra. The calculations include the spectra arising from non α-helical molecules and molecules with non-uniform intrinsic mobility. In a first step, dipolar or quadrupolar interaction tensors drive molecular rotations and reorientations to obtain the proper mean values as observed in corresponding NMR experiments. In a second step, the coordinate snapshots of the MDOC simulations are geometry optimized with the isotropic 15N chemical shifts as constraints using Bond Polarization Theory (BPT) to provide reliable 15N CS tensor data. The averaged dipolar 1H-15N couplings and the δzz tensor components can then be combined to simulate PISEMA patterns. We apply this method to the ß-helical peptide gramicidin A (gA) and demonstrate that this method enables the assignment of most PISEMA resonances. In addition, MDOC simulations provide local order parameters for the calculated sites. These local order parameters reveal large differences in backbone mobility between L- and D-amino acids of gA.

固态NMR被广泛用于研究脂质双层中蛋白质和肽的取向和其他结构特征。利用PISEMA(魔角极化反转自旋交换)实验获得的数据,周期性光谱模式由排列良好的α-螺旋分子产生。对于没有形成完美定义的二级结构(如α-螺旋)的系统,或者信号模式受到分子运动干扰的系统,在解释PISEMA光谱时可能会出现重大问题。在这里,我们提出了一种新的方法,将分子动力学模拟与张量取向约束(MDOC)和化学位移张量计算相结合,用于模拟和解释类PISEMA光谱。计算包括非α-螺旋分子和具有非均匀本征迁移率的分子产生的光谱。在第一步中,偶极或四极相互作用张量驱动分子旋转和重定向,以获得在相应NMR实验中观察到的适当平均值。在第二步中,使用键极化理论(BPT)以各向同性15N化学位移作为约束对MDOC模拟的坐标快照进行几何优化,以提供可靠的15N CS张量数据。然后可以将平均偶极1H-15N耦合和δzz张量分量组合起来模拟PISEMA模式。我们将该方法应用于ß-螺旋肽gramicidin A(gA),并证明该方法能够分配大多数PISEMA共振。此外,MDOC模拟为计算的站点提供了局部阶数参数。这些局部序参数揭示了gA的L-和D-氨基酸之间主链迁移率的巨大差异。
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引用次数: 0
Molecular precursors to produce para-hydrogen enhanced metabolites at any field 在任何领域产生对氢增强代谢产物的分子前体。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-10-11 DOI: 10.1002/mrc.5402
Anil P. Jagtap, Salvatore Mamone, Stefan Glöggler

Enhancing magnetic resonance signal via hyperpolarization techniques enables the real-time detection of metabolic transformations even in vivo. The use of para-hydrogen to enhance 13C-enriched metabolites has opened a rapid pathway for the production of hyperpolarized metabolites, which usually requires specialized equipment. Metabolite precursors that can be hyperpolarized and converted into metabolites at any given field would open up opportunities for many labs to make use of this technology because already existing hardware could be used. We report here on the complete synthesis and hyperpolarization of suitable precursor molecules of the side-arm hydrogenation approach. The better accessibility to such side-arms promises that the para-hydrogen approach can be implemented in every lab with existing two channel NMR spectrometers for 1H and 13C independent of the magnetic field.

通过超极化技术增强磁共振信号,即使在体内也能实时检测代谢转化。使用对氢来增强13种富含C的代谢物为产生超极化代谢物开辟了一条快速途径,这通常需要专门的设备。可以在任何特定领域超极化并转化为代谢物的代谢物前体将为许多实验室利用这项技术开辟机会,因为可以使用现有的硬件。我们在这里报道了侧臂氢化方法的合适前体分子的完全合成和超极化。这种侧臂的更好可达性保证了对氢方法可以在每个实验室中实施,现有的1H和13C的双通道NMR光谱仪独立于磁场。
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引用次数: 0
Low-field, not low quality: 1D simplification, selective detection, and heteronuclear 2D experiments for improving low-field NMR spectroscopy of environmental and biological samples 低场,而不是低质量:1D简化、选择性检测和异核2D实验,用于改进环境和生物样品的低场NMR光谱。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-10-09 DOI: 10.1002/mrc.5401
Katelyn Downey, Wolfgang Bermel, Ronald Soong, Daniel H. Lysak, Kiera Ronda, Katrina Steiner, Peter M. Costa, William W. Wolff, Venita Decker, Falko Busse, Benjamin Goerling, Agnes Haber, Myrna J. Simpson, Andre J. Simpson

Understanding environmental change is challenging and requires molecular-level tools to explain the physicochemical phenomena behind complex processes. Nuclear magnetic resonance (NMR) spectroscopy is a key tool that provides information on both molecular structures and interactions but is underutilized in environmental research because standard “high-field” NMR is financially and physically inaccessible for many and can be overwhelming to those outside of disciplines that routinely use NMR. “Low-field” NMR is an accessible alternative but has reduced sensitivity and increased spectral overlap, which is especially problematic for natural, heterogeneous samples. Therefore, the goal of this study is to investigate and apply innovative experiments that could minimize these challenges and improve low-field NMR analysis of environmental and biological samples. Spectral simplification (JRES, PSYCHE, singlet-only, multiple quantum filters), selective detection (GEMSTONE, DREAMTIME), and heteronuclear (reverse and CH3/CH2/CH-only HSQCs) NMR experiments are tested on samples of increasing complexity (amino acids, spruce resin, and intact water fleas) at-high field (500 MHz) and at low-field (80 MHz). A novel experiment called Doubly Selective HSQC is also introduced, wherein 1H signals are selectively detected based on the 1H and 13C chemical shifts of 1H–13C J-coupled pairs. The most promising approaches identified are the selective techniques (namely for monitoring), and the reverse and CH3-only HSQCs. Findings ultimately demonstrate that low-field NMR holds great potential for biological and environmental research. The multitude of NMR experiments available makes NMR tailorable to nearly any research need, and low-field NMR is therefore anticipated to become a valuable and widely used analytical tool moving forward.

理解环境变化具有挑战性,需要分子水平的工具来解释复杂过程背后的物理化学现象。核磁共振(NMR)光谱是一种提供分子结构和相互作用信息的关键工具,但在环境研究中没有得到充分利用,因为标准的“高场”NMR在经济和物理上对许多人来说都是不可获得的,并且对那些常规使用NMR的学科之外的人来说可能是压倒性的。“低场”NMR是一种可供选择的方法,但灵敏度降低,光谱重叠增加,这对天然、异质样品来说尤其有问题。因此,本研究的目标是研究和应用创新实验,以最大限度地减少这些挑战,并改进环境和生物样品的低场NMR分析。在高场(500 MHz)和低场(80 MHz)。还介绍了一种称为双选择性HSQC的新实验,其中基于1H-13C J耦合对的1H和13C化学位移选择性地检测1H信号。确定的最有前景的方法是选择性技术(即监测),以及反向和仅CH3的HSQC。研究结果最终表明,低场核磁共振在生物和环境研究中具有巨大的潜力。大量的核磁共振实验使核磁共振几乎可以满足任何研究需求,因此低场核磁共振有望成为一种有价值且广泛使用的分析工具。
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引用次数: 0
Studying the interaction of glycans with intact virions and virus-like particles by ligand-observed NMR spectroscopy 通过配体观察NMR光谱研究聚糖与完整病毒粒子和病毒样颗粒的相互作用。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-09-30 DOI: 10.1002/mrc.5399
Thomas Haselhorst

Virus-glycan interactions play a crucial role in the infection process of many viruses. NMR spectroscopy has emerged as a powerful tool for studying these interactions at the molecular level. In this article, we review several published papers and reports that have highlighted the application of NMR spectroscopy in understanding the complex questions of how viruses engage with and bind to receptor glycans. The use of saturation transfer difference (STD) NMR spectroscopy has demonstrated itself as highly advantageous in investigating the interaction between glycans and intact virions or virus-like particles (VLPs). The broad NMR signal linewidth of virions and VLPs allows efficient saturation without affecting the glycan signals. The advantage of this approach is that the viral capsid environment in protein organization and function is not ignored and therefore provides a more biologically relevant model for exploring the interactions between the virus and the host cell glycans. We will review some examples of using NMR spectroscopy to study influenza cell tropism, rotaviruses, and noroviruses.

病毒聚糖相互作用在许多病毒的感染过程中起着至关重要的作用。核磁共振波谱已经成为在分子水平上研究这些相互作用的强大工具。在这篇文章中,我们回顾了几篇已发表的论文和报告,这些论文和报告强调了核磁共振波谱在理解病毒如何与受体聚糖结合的复杂问题中的应用。饱和转移差(STD)NMR光谱的使用已经证明在研究聚糖与完整病毒粒子或病毒样颗粒(VLP)之间的相互作用方面是非常有利的。病毒粒子和VLP的宽NMR信号线宽允许有效饱和而不影响聚糖信号。这种方法的优点是不忽视蛋白质组织和功能中的病毒衣壳环境,因此为探索病毒和宿主细胞聚糖之间的相互作用提供了一个更具生物学相关性的模型。我们将回顾一些使用核磁共振波谱来研究流感细胞嗜性、轮状病毒和诺如病毒的例子。
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引用次数: 0
Characterization of fatty acid forms using benchtop NMR in omega-3 oil supplements 在ω-3油补充剂中使用台式NMR表征脂肪酸形式。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-09-22 DOI: 10.1002/mrc.5398
Carla Remy, Saïda Danoun, Mathieu Delample, Cameron Morris, Véronique Gilard, Stéphane Balayssac

Omega-3 fatty acid supplements, such as fish oil and plant-based oils, have gained popularity because of their potential health benefits. However, the quality and composition of these supplements can vary widely, particularly in terms of the two main forms of omega-3 fatty acids: triacylglycerols (TAGs) and ethyl esters (EEs). TAGs are the natural form found in fish oil but are prone to oxidation, whereas EEs are more stable but less well absorbed by the body. Differentiating between these forms is crucial for assessing the efficacy and tolerance of omega-3 supplements. This article describes a novel approach to differentiate between TAG and EE forms of omega-3 fatty acids in dietary supplements, utilizing a 60-MHz benchtop nuclear magnetic resonance (NMR) spectrometer. The proposed method using 1H and 1H-1H COSY NMR provides a quick and accurate approach to screen the forms of omega-3 fatty acids and evaluate their ratios. The presence of diacylglycerol (DAGs) in some supplements was also highlighted by this method and adds some information about the process used (i.e., esterification/enrichment). The affordability and user-friendliness of benchtop NMR equipment make this method feasible for food processing companies or quality control laboratories. In this study, 24 oil supplements were analyzed using NMR analysis in order to demonstrate the potential of this method for the differentiation of TAG and EE forms in omega-3 supplements.

鱼油和植物油等Omega-3脂肪酸补充剂因其潜在的健康益处而广受欢迎。然而,这些补充剂的质量和成分可能差异很大,特别是在两种主要形式的ω-3脂肪酸方面:三酰基甘油(TAGs)和乙酯(EE)。TAG是鱼油中的天然形式,但容易被氧化,而EEs更稳定,但不太容易被身体吸收。区分这些形式对于评估ω-3补充剂的疗效和耐受性至关重要。本文描述了一种利用60 MHz台式核磁共振(NMR)光谱仪区分膳食补充剂中ω-3脂肪酸TAG和EE形式的新方法。所提出的使用1H和1H-1H COSY NMR的方法提供了一种快速准确的方法来筛选ω-3脂肪酸的形式并评估其比率。该方法还强调了一些补充剂中二酰基甘油(DAG)的存在,并添加了有关所用过程(即酯化/富集)的一些信息。台式核磁共振设备的经济性和用户友好性使这种方法对于食品加工公司或质量控制实验室来说是可行的。在这项研究中,使用NMR分析对24种油补充剂进行了分析,以证明该方法在ω-3补充剂中分化TAG和EE形式的潜力。
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引用次数: 0
Reaction monitoring via benchtop nuclear magnetic resonance spectroscopy: A practical comparison of on-line stopped-flow and continuous-flow sampling methods 通过台式核磁共振波谱进行反应监测:在线停流和连续流采样方法的实际比较。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-09-22 DOI: 10.1002/mrc.5395
Tristan Maschmeyer, David J. Russell, José G. Napolitano, Jason E. Hein

The ability for nuclear magnetic resonance (NMR) spectroscopy to provide quantitative, structurally rich information makes this spectroscopic technique an attractive reaction monitoring tool. The practicality of NMR for this type of analysis has only increased in the recent years with the influx of commercially available benchtop NMR instruments and compatible flow systems. In this study, we aim to compare 19F NMR reaction profiles acquired under both on-line continuous-flow and stopped-flow sampling methods, with modern benchtop NMR instrumentation, and two reaction systems: a homogeneous imination reaction and a biphasic activation of a carboxylic acid to acyl fluoride. Reaction trends with higher data density can be acquired with on-line continuous-flow analyses, and this work highlights that representative reaction trends can be acquired without any correction when monitoring resonances with a shorter spin–lattice relaxation time (T1), and with the used flow conditions. On-line stopped-flow analyses resulted in representative reaction trends in all cases, including the monitoring of resonances with a long T1, without the need of any correction factors. The benefit of easier data analysis, however, comes with the cost of time, as the fresh reaction solution must be flowed into the NMR system, halted, and time must be provided for spins to become polarized in the instrument's external magnetic field prior to spectral measurement. Results for one of the reactions were additionally compared with the use of a high-field NMR.

核磁共振(NMR)光谱提供定量、结构丰富的信息的能力使这种光谱技术成为一种有吸引力的反应监测工具。近年来,随着商用台式NMR仪器和兼容的流动系统的涌入,NMR在这类分析中的实用性才有所提高。在这项研究中,我们的目的是比较在在线连续流和停流采样方法下获得的19F NMR反应谱,使用现代台式NMR仪器,以及两种反应系统:均相激发光反应和羧酸向酰氟的双相活化。通过在线连续流动分析可以获得具有更高数据密度的反应趋势,这项工作强调,当用更短的自旋晶格弛豫时间(T1)和所用的流动条件监测共振时,可以在没有任何校正的情况下获得代表性的反应趋势。在线停流分析在所有情况下都产生了具有代表性的反应趋势,包括在不需要任何校正因子的情况下监测具有长T1的共振。然而,更容易的数据分析带来的好处是时间成本,因为新鲜的反应溶液必须流入NMR系统,停止,并且在光谱测量之前,必须为自旋在仪器的外部磁场中极化提供时间。另外将其中一个反应的结果与使用高场NMR进行比较。
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引用次数: 0
J-filter: An experiment to simplify and isolate specific signals in 1H NMR spectra of complex mixtures based on scalar coupling constants J-filter:基于标量耦合常数简化和分离复杂混合物1H NMR光谱中特定信号的实验
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-09-19 DOI: 10.1002/mrc.5396
Karen V. Góñez, Juan Suárez García, F. Javier Sardina, Yolanda Pazos, Ángela Saá, Manuel Martín−Pastor

One-dimensional selective NMR experiments relying on a J-filter element are proposed to isolate specific signals in crowded 1H spectral regions. The J-filter allows the edition or filtering of signals in a region of interest of the spectrum by exploiting the specific values of their 1H-1H coupling constants and certain parameters of protons coupled to them that appear in less congested parts of the spectrum (chemical shifts and coupling constants). The new experiments permitted the isolation of specific peaks of phytosterol components in a sample obtained from a liquid nutraceutical recommended for lowering blood cholesterol levels in regions with complete overlap in the 1H spectrum.

提出了依赖于J滤波器元件的一维选择性NMR实验来分离拥挤的1H光谱区域中的特定信号。J滤波器允许通过利用其1H-1H耦合常数的特定值和与之耦合的质子的某些参数(化学位移和耦合常数)来编辑或过滤光谱的感兴趣区域中的信号,这些参数出现在光谱的不太拥挤的部分中。新的实验允许在1H光谱完全重叠的区域分离从液体营养品中获得的样品中的植物甾醇组分的特定峰,该液体营养品被推荐用于降低血液胆固醇水平。
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引用次数: 0
Quantitative NMR using water as internal calibrant 定量核磁共振使用水作为内校准
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-09-19 DOI: 10.1002/mrc.5394
Bosong Xiang

A new quantitative nuclear magnetic resonance (qNMR) method, called qNMRw, using water as the internal calibrant has been developed. Its principles, procedures, calculations, and test results are presented here. It is shown to avoid the difficulties created by moisture present in other reference materials. High precision and accuracy can be achieved with qNMRw. The method can be used for analyzing technical materials, herbicide formulation products, and other types of chemical samples. It can also be used to measure the purity and concentration of materials to be used as quantitation calibrants.

开发了一种新的定量核磁共振(qNMR)方法,称为qNMRw,使用水作为内标物。这里介绍了它的原理、程序、计算和测试结果。它被证明可以避免其他参考材料中存在的水分所造成的困难。使用qNMRw可以实现高精度和高精度。该方法可用于分析技术材料、除草剂配方产品和其他类型的化学样品。它还可用于测量用作定量校准品的材料的纯度和浓度。
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引用次数: 0
Charting the solid-state NMR signals of polysaccharides: A database-driven roadmap 绘制多糖的固态NMR信号图:数据库驱动的路线图。
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-09-19 DOI: 10.1002/mrc.5397
Wancheng Zhao, Debkumar Debnath, Isha Gautam, Liyanage D. Fernando, Tuo Wang

Solid-state nuclear magnetic resonance (ssNMR) measurements of intact cell walls and cellular samples often generate spectra that are difficult to interpret due to the presence of many coexisting glycans and the structural polymorphism observed in native conditions. To overcome this analytical challenge, we present a statistical approach for analyzing carbohydrate signals using high-resolution ssNMR data indexed in a carbohydrate database. We generate simulated spectra to demonstrate the chemical shift dispersion and compare this with experimental data to facilitate the identification of important fungal and plant polysaccharides, such as chitin and glucans in fungi and cellulose, hemicellulose, and pectic polymers in plants. We also demonstrate that chemically distinct carbohydrates from different organisms may produce almost identical signals, highlighting the need for high-resolution spectra and validation of resonance assignments. Our study provides a means to differentiate the characteristic signals of major carbohydrates and allows us to summarize currently undetected polysaccharides in plants and fungi, which may inspire future investigations.

完整细胞壁和细胞样品的固态核磁共振(ssNMR)测量通常产生难以解释的光谱,这是由于存在许多共存的聚糖和在天然条件下观察到的结构多态性。为了克服这一分析挑战,我们提出了一种使用碳水化合物数据库中索引的高分辨率ssNMR数据分析碳水化合物信号的统计方法。我们生成模拟光谱来证明化学位移分散,并将其与实验数据进行比较,以便于鉴定重要的真菌和植物多糖,如真菌中的几丁质和葡聚糖,以及植物中的纤维素、半纤维素和果胶聚合物。我们还证明,来自不同生物体的化学性质不同的碳水化合物可能会产生几乎相同的信号,这突出了对高分辨率光谱和共振分配验证的需求。我们的研究提供了一种区分主要碳水化合物特征信号的方法,并使我们能够总结目前在植物和真菌中未被发现的多糖,这可能会启发未来的研究。
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引用次数: 0
Pure shift FESTA: An ultra-high resolution NMR tool for the analysis of complex fluorine-containing spin systems 纯移FESTA:用于分析复杂含氟自旋系统的超高分辨率核磁共振工具
IF 2 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2023-09-09 DOI: 10.1002/mrc.5393
Coral Mycroft, Marshall J. Smith, Mathias Nilsson, Gareth A. Morris, Laura Castañar

NMR measurements of molecules containing sparse fluorine atoms are becoming increasingly common due to their prevalence in medicinal chemistry. However, the presence of both homonuclear and heteronuclear scalar couplings severely complicates their analysis by NMR. In complex systems, FESTA, a heteronuclear spectral editing method, allows simplified 1H NMR spectra to be obtained containing only 1H signals from the same spin system as a chosen 19F. Despite spectral simplification, signal overlap due to the presence of scalar couplings is often a problem in FESTA spectra. Here, we report a new experiment that combines FESTA and pure shift methods to provide fully decoupled ultra-high resolution FESTA spectra showing a single signal for each 1H chemical environment. The utility of the method is demonstrated for the analysis of two complex fluorine-containing mixtures of pharmaceutical and biochemical interest.

含有稀疏氟原子的分子的核磁共振测量由于其在药物化学中的流行而变得越来越普遍。然而,同核和异核标量耦合的存在严重复杂化了它们的核磁共振分析。在复杂系统中,FESTA是一种异核谱编辑方法,它可以获得简化的1H NMR谱,其中只包含与选定的19F相同自旋系统的1H信号。尽管频谱简化,信号重叠由于标量耦合的存在往往是一个问题,在FESTA光谱。在这里,我们报告了一个新的实验,结合FESTA和纯移位方法,提供完全解耦的超高分辨率FESTA光谱,显示每个1H化学环境的单个信号。该方法的实用性证明了两种复杂的含氟混合物的药物和生化兴趣的分析。
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引用次数: 0
期刊
Magnetic Resonance in Chemistry
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