Accelerated Nuclear Magnetic Resonance Spectroscopy with Deep Learning

Nuclear magnetic resonance (NMR) spectroscopy serves as an indispensable tool in chemistry and biology but often suffers from long experimental times. We present a proof-of-concept of the application of deep learning and neural networks for high-quality, reliable, and very fast NMR spectra reconstruction from limited experimental data. We show that the neural network training can be achieved using solely synthetic NMR signals, which lifts the prohibiting demand for a large volume of realistic training data usually required for a deep learning approach.     

Accelerated Nuclear Magnetic Resonance Spectroscopy with Deep Learning

Nuclear magnetic resonance (NMR) spectroscopy serves as an indispensable tool in chemistry and biology but often suffers from long experimental times. We present a proof‐of‐concept of the application of deep learning and neural networks for high‐quality, reliable, and very fast NMR spectra reconstruction from limited experimental data. We show that the neural network training can be achieved using solely synthetic NMR signals, which lifts the prohibiting demand for a large volume of realistic training data usually required for a deep learning approach.     

Review and Prospect: Deep Learning in Nuclear Magnetic Resonance Spectroscopy

Since the concept of deep learning (DL) was formally proposed in 2006, it has had a major impact on academic research and industry. Nowadays, DL provides an unprecedented way to analyze and process data with demonstrated great results in computer vision, medical imaging, natural language processing, and so forth. Herein, applications of DL in NMR spectroscopy are summarized, and a perspective for DL as an entirely new approach that is likely to transform NMR spectroscopy into a much more efficient and powerful technique in chemistry and life sciences is outlined.     

Nuclear Magnetic Resonance in Solid-State Chemistry

Various problems of solid-state chemistry can be solved by spectroscopic investigation of the nuclear magnetic resonance (NMR and NQR methods). This progress report presents a survey of the nature of the interactions in the crystal that underlie such measurements, of the observations in the spectrum, and of the information obtainable from it. The field of application of the methods covers both static and dynamic properties of solids.     

Fourier Transform Nuclear Magnetic Resonance Spectroscopy of Commercial Polysiloxanes

Abstract

Multinuclear Fourier transform nmr spectroscopy is shown to be a potentially useful technique for the evaluation of commercial polysiloxanes. H, ²⁹Si: and ¹³C nmr spectra are reported of the precursor solutions for RTV silicones. The ¹³C show the increased presence of an unidentified material in unacceptable lots of one of the two precursor solutions.     

Methods and Applications of Nuclear Magnetic Double Resonance

In double resonance spectra, transitions between energy levels of a nuclear spin system are measured in the presence of two (or more) oscillating magnetic fields. Experiments of this nature form the basis of what is nowadays one of the most important techniques of NMR spectroscopy. Depending on the method selected, they can be used to unravel complex spectra, to measure hidden or weak resonances, or to determine the relative signs of coupling constants, as well as in stereochemical or kinetic studies. This wide and steadily growing range of applications of double resonance is described with the aid of specifilc examples.     

核磁共振技术(NMR)在组合化学中的应用

对科学产生最大影响的分析方法是核磁共振技术(NMR),它被广泛用于许多领域.本文结合作者的研究结果评述了NMR在组合化学中的应用,着重于NMR在固相合成的应用、液态NMR和NMR在高通量筛选中的应用.     

活泼氢的核磁共振氢谱

核磁共振氢谱是有机化合物结构表征中最常使用的波谱方法之一,提供了有机化合物质子的化学位移、积分面积和耦合裂分等信息。常见的活泼氢是与氧、氮和硫共价相连的氢原子,存在着快速交换机制,与碳上的氢有显著的差异。在不同条件下活泼氢化学位移不固定、峰形多变并且耦合裂分情况复杂。本文探讨了如何通过核磁共振氢谱解析活泼氢,培养学生对谱图进行观察、分析以及结构推导的能力。     

核磁共振扩散序谱的研究及应用进展

核磁共振(NMR)是确定分子结构最常用的分析方法之一,扩散序谱(DOSY)拓展了核磁共振波谱分析复杂混合物的能力。DOSY可以通过测量混合物的自扩散系数,"虚拟分离"多组分系统中的各化学实体。而自扩散系数反映了分子的有效大小和形状,因此DOSY也能提供分子尺寸、分子量、分子间相互作用及聚集状态的具体信息。该文综述了DOSY实验的基本原理、脉冲序列发展及相关研究领域的应用进展。首先简述了脉冲场梯度、脉冲序列的发展及应用特点,然后详细介绍了DOSY在鉴别混合物组分、测量分子尺寸、分子量分布、表征分子间作用力等方面的研究进展。通过实例展示了DOSY在化学、药学、食品、生物等领域的广泛应用。     

Billion‐Fold Enhancement in Sensitivity of Nuclear Magnetic Resonance Spectroscopy for Magnesium Ions in Solution

β‐nuclear magnetic resonance (NMR) spectroscopy is highly sensitive compared to conventional NMR spectroscopy, and may be applied for several elements across the periodic table. β‐NMR has previously been successfully applied in the fields of nuclear and solid‐state physics. In this work, β‐NMR is applied, for the first time, to record an NMR spectrum for a species in solution. ³¹Mg β‐NMR spectra are measured for as few as 10⁷ magnesium ions in ionic liquid (EMIM‐Ac) within minutes, as a prototypical test case. Resonances are observed at 3882.9 and 3887.2 kHz in an external field of 0.3 T. The key achievement of the current work is to demonstrate that β‐NMR is applicable for the analysis of species in solution, and thus represents a novel spectroscopic technique for use in general chemistry and potentially in biochemistry.     

On‐Line Monitoring of Chemical Reactions by using Bench‐Top Nuclear Magnetic Resonance Spectroscopy

Real‐time nuclear magnetic resonance (NMR) spectroscopy measurements carried out with a bench‐top system installed next to the reactor inside the fume hood of the chemistry laboratory are presented. To test the system for on‐line monitoring, a transfer hydrogenation reaction was studied by continuously pumping the reaction mixture from the reactor to the magnet and back in a closed loop. In addition to improving the time resolution provided by standard sampling methods, the use of such a flow setup eliminates the need for sample preparation. Owing to the progress in terms of field homogeneity and sensitivity now available with compact NMR spectrometers, small molecules dissolved at concentrations on the order of 1 mmol L^?1 can be characterized in single‐scan measurements with 1 Hz resolution. Owing to the reduced field strength of compact low‐field systems compared to that of conventional high‐field magnets, the overlap in the spectrum of different NMR signals is a typical situation. The data processing required to obtain concentrations in the presence of signal overlap are discussed in detail, methods such as plain integration and line‐fitting approaches are compared, and the accuracy of each method is determined. The kinetic rates measured for different catalytic concentrations show good agreement with those obtained with gas chromatography as a reference analytical method. Finally, as the measurements are performed under continuous flow conditions, the experimental setup and the flow parameters are optimized to maximize time resolution and signal‐to‐noise ratio.     

脂肪胺聚氧乙基醚结构的核磁共振波谱表征

从工业和合成产品脂肪胺聚氧乙基醚中用TLC和快速色谱(FC)分离精制得到6个脂肪胺聚氧乙基醚模型化合物，用^1H、^13C、gCOSY，gHSQC和gHMBC等核磁共振波谱和质谱表征了其结构，完成了^1H和^13C NMR谱带的归属，为本系列化合物的结构和EO分布鉴定提供了依据，并给出了计算本系列化合物叔胺值的方法。考察了酸性条件对脂肪胺聚氧乙基醚化合物相关基团化学位移的影响。     

核磁共振波谱法测定聚环戊烯橡胶的微观结构

采用核磁共振波谱法对聚环戊烯橡胶进行一维氢谱和碳谱分析,结合二维核磁HSQC(Heteronuclear Single Quantum Coherence)方法,对聚环戊烯橡胶顺反异构体核磁谱峰进行归属。建立了聚环戊烯橡胶顺反异构体含量计算公式,根据该公式计算得到聚环戊烯橡胶顺反异构体含量。将本方法定量结果与红外法定量结果进行比对,结果显示,核磁共振波谱法更适合于聚环戊烯橡胶顺反异构体定量分析。     

Analysis of Cyclocitral Mixtures by Nuclear Magnetic Resonance Spectroscopy

Abstract

Adequately separated signals in the nuclear megnetic resonance spectra of mixtures of cyclocitrals were assigned to the individual components. This assignment allowed direct integration of the signals of interst and calculation of the percentages of α-cyclocitral, β-cyclocitral, para-cymene, and 1-acetyl-4, 4-dimethyl-1-cyclohexene. The rapidity and nondestructive nature of the nuclear magnetic resonance analysis are superior to the fractional crystallization of the semi-carbazones and gas chromatography techniques previously utilized.     

Cos-7细胞胞内pH的31 P核磁共振测定

生物细胞内pH的测定对于细胞内代谢、游离离子及离子通道的研究有重要的意义,而且一些酶的活性也与细胞内pH密切相关。猴的肾细胞cos-7细胞常用于外源基因的转染表达,研究这一细胞株细胞内的pH,可为基因转染提供可靠的依据。本文采用^31P核磁共振对cos-7细胞胞内的pH进行了分析测定。