Fast 2D NMR Research Articles

NMR methods for the analysis of mixtures.

NMR spectroscopy is a powerful approach for the analysis of mixtures. Its usefulness arises in large part from the vast landscape of methods, and corresponding pulse sequences, that have been and are being designed to tackle the specific properties of mixtures of small molecules. This feature article describes a selection of methods that aim to address the complexity, the low concentrations, and the changing nature that mixtures can display. These notably include pure-shift and diffusion NMR methods, hyperpolarisation methods, and fast 2D NMR methods such as ultrafast 2D NMR and non-uniform sampling. Examples or applications are also described, in fields such as reaction monitoring and metabolomics, to illustrate the relevance and limitations of different methods.

Comparison of Regular, Pure Shift, and Fast 2D NMR Experiments for Determination of the Geographical Origin of Walnuts

1H NMR spectroscopy, in combination with chemometric methods, was used to analyze the methanol/acetonitrile (1:1) extract of walnut (Juglans Regia L.) regarding the geographical origin of 128 authentic samples from different countries (France, Germany, China) and harvest years (2016–2019). Due to the large number of different metabolites within the acetonitrile/methanol extract, the one-dimensional (1D) 1H NOESY (nuclear Overhauser effect spectroscopy) spectra suffer from strongly overlapping signals. The identification of specific metabolites and statistical analysis are complicated. The use of pure shift 1H NMR spectra such as PSYCHE (pure shift yielded by chirp excitation) or two-dimensional ASAP-HSQC (acceleration by sharing adjacent polarization-heteronuclear single quantum correlation) spectra for multivariate analysis to determine the geographical origin of foods may be a promising method. Different types of NMR spectra (1D 1H NOESY, PSYCHE, and ASAP-HSQC) were acquired for each of the 128 walnut samples and the results of the statistical analysis were compared. A support vector machine classifier was applied for differentiation of samples from Germany/China, France/Germany, and France/China. The models obtained by conduction of a repeated nested cross-validation showed accuracies from 58.9% (±1.3%) to 95.9% (±0.8%). The potential of the 1H-13C HSQC as a 2D NMR experiment for metabolomics studies was shown.

Microstructure determination of ethylene-styrene-1-hexene terpolymers with fast 2D NMR by nonuniform sampling

A series of poly(ethylene-styrene-hexene) samples with relatively low glass-transition temperatures (Tg = −38 ‒28 °C) were synthesized using Me2Si(Me4Cp)(N-t-Bu)TiCl2/MMAO system. For the first time, nonuniform sampling with 2D-1H/13C HSQC and HMBC experimentsis employed to determine the microstructure of these complicated terpolymers. The signals hiddenin the specta overlaps are clearly discriminated, and the assignments of new peaksfrom novel sequences are successfully achieved with about 50% of conventional experiment time. The distributionsof 11 triads are quantatively presented. The results demonstrate that 2D NMR with nonuniform sampling is superior to the traditional uniform sampling approaches in terms of resolution, experiment time, signal-to-noise ratio and structural information gathered, and this approach represents a fast way for microstructure determination of complicated synthetic polymers.

High-throughput authentication of edible oils with benchtop Ultrafast 2D NMR

We report the use of an Ultrafast 2D NMR approach applied on a benchtop NMR system (43 MHz) for the authentication of edible oils. Our results demonstrate that a profiling strategy based on fast 2D NMR spectra recorded in 2.4 min is more efficient than the standard 1D experiments to classify oils from different botanical origins, since 1D spectra on the same samples suffer from strong peak overlaps. Six edible oils with different botanical origins (olive, hazelnut, sesame, rapeseed, corn and sunflower) have been clearly discriminated by PCA analysis. Furthermore, we show how this approach combined with a PLS model can detect adulteration processes such as the addition of hazelnut oil into olive oil, a common fraud in food industry.

Absolute quantification of metabolites in tomato fruit extracts by fast 2D NMR

Quantitative NMR metabolomics is a powerful tool to have access to valuable information on metabolism. Unfortunately, the quantitative analysis of metabolic samples is often hampered by peak overlap. Two-dimensional (2D) spectroscopy offers a promising alternative and quantitative results can be obtained provided that a calibration approach is employed. However, the duration of 2D NMR experiments is barely compatible with the metabolomic study of a large number of samples. This drawback can be circumvented by relying on “ultrafast” experiments capable of recording 2D spectra in a single-scan. While such experiments are not sensitive enough to match the concentrations of metabolic samples, a compromise can be reached by hybrid strategies capable of recording 2D NMR spectra of extracts in a few minutes only. The purpose of this study is to demonstrate that these multi-scan single-shot experiments can be successfully applied to the absolute quantification of major metabolites in plant extracts. Fast COSY experiments are recorded in 5 min on tomato fruit pericarp extracts at different stages of development. The concentration of eight major metabolites is determined with a trueness better than 10 % and a technical repeatability of a few percent. The experiments performed at two magnetic fields lead to similar quantitative results, in coherence with the metabolism of tomato fruit. The results show that fast 2D NMR methods form a promising tool for fast targeted metabolomics, and open promising perspective towards the automated and high-throughput quantitative analysis of large groups of plant and other samples for metabolomics and for the modelling of metabolism.

Analytical Currents: Counting rare tumor cells in vivo | Nano-optode sensors are brighter than QDs and biocompatible | Optical microcavities for detecting single molecules | Protein folding by fast 2D NMR spectroscopy | Separation by solid-supported bilayer electrophoresis | Raman microspectroscopy of mitochondria

ADVERTISEMENT RETURN TO ISSUEPREVNEWSNEXTAnalytical Currents: Counting rare tumor cells in vivo | Nano-optode sensors are brighter than QDs and biocompatible | Optical microcavities for detecting single molecules | Protein folding by fast 2D NMR spectroscopy | Separation by solid-supported bilayer electrophoresis | Raman microspectroscopy of mitochondriaCite this: Anal. Chem. 2007, 79, 17, 6427–6429Publication Date (Web):September 1, 2007Publication History Published online1 September 2007Published inissue 1 September 2007https://doi.org/10.1021/ac071953jRIGHTS & PERMISSIONSArticle Views369Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (352 KB) Get e-AlertsSUBJECTS:Cells,Protein folding,Quantum dots,Sensors,Vesicles Get e-Alerts

Structure Elucidation of Secalosides A and B by NMR Spectroscopy

The constitution of secalosides A and B was elucidated through NMR spectroscopy using fast 2D-NMR experiments with pulsed-field gradients for coherence selection. Secalosides A and B are epimers at center C-3‘ of aglycon I and have the constitution shown as 1. The presence of a saccharose unit was confirmed independently by mild basic hydrolysis and enzymatic quantification. The relative configuration of the stereogenic centers of aglycon II could be deduced from ROESY data. Assignments of the two epimers to the R- and S- configurations at C-3‘ in aglycon I, as well as the absolute configuration of aglycon II remain to be determined.