Using indirect covariance processing for structure elucidation of small molecules in cases of spectral crowding

Aspers, Ruud L. E. G.; Geutjes, Pepijn E. T. J.; Honing, Maarten; Jaeger, Martin

doi:10.1002/mrc.2766

Cited by 19 publications

(10 citation statements)

References 66 publications

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“…Where there is sufficient signal-to-noise ratio, either conventional or covariance [17,18] heteronuclear correlation methods are other possibilities, whereas in extreme cases using covariance processing to combine heteronuclear and pure shift homonuclear correlation would be particularly powerful. Almost all common 2D NMR experiments can be adapted to use such decoupling methods.…”

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confidence: 99%

“…The choice of method will, as noted above, depend on the sample concentration and instrument sensitivity available. Where there is sufficient signal-to-noise ratio, either conventional or covariance [17,18] heteronuclear correlation methods are other possibilities, whereas in extreme cases using covariance processing to combine heteronuclear and pure shift homonuclear correlation would be particularly powerful.…”

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confidence: 99%

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Decoupling Two‐Dimensional NMR Spectroscopy in Both Dimensions: Pure Shift NOESY and COSY

et al. 2012

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Spectral assignment is a crucial step in the analysis of chemical structure by NMR spectroscopy, but is often limited by signal overlap. If the multiplet structure caused by spinspin coupling is suppressed, spectral resolution can be greatly increased, and the process of assignment correspondingly simplified. Collapsing a multiplet to a single "pure shift" peak can be achieved using a variety of methods, as has been demonstrated in 1D NMR spectroscopy, and in one dimension of several different homonuclear 2D experiments. [1][2][3][4][5][6][7][8][9][10] Recently, it has been shown that applying covariance processing to a TOCSY dataset decoupled in one dimension gives a fully decoupled 2D spectrum. [11] Previous routes to fully decoupled 2D spectra have used pattern recognition postprocessing applied to conventional, fully coupled 2D data. [12][13][14] The considerably increased resolution in, and simplicity of, fully decoupled 2D spectra makes them particularly attractive for automated structure elucidation.Here we compare two different decoupling methods, illustrating the very general nature, and potential for resolution gain, of pure shift covariance NMR spectroscopy, by applying different single decoupling methods to the NOESY and nQF-COSY experiments, producing doubly pure shift 2D spectra by covariance processing. Using pure shift acquisition for one spectral dimension greatly improves resolution, collapsing multiplet structure to singlets, whereas the use of covariance processing gives a further gain in interpretability by condensing the correlation information into 2D singlets.Methods for achieving broadband homonuclear decoupling in 2D NMR spectroscopy include the Zangger-Sterk (ZS) experiment and its adaptations; [1][2][3][4] the Pell-Keeler (PK) 458 projection of phase-sensitive 2D-J data; [5] the "BIRD" (bilinear rotation decoupling) family of sequence elements; [6,7] and the "constant time" (CT) approach. [8][9][10] All such methods trade sensitivity for resolution, to a greater or lesser extent. The first three methods are appropriate for experiments that generate in-phase cross-peaks, whereas CT

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Decoupling Two‐Dimensional NMR Spectroscopy in Both Dimensions: Pure Shift NOESY and COSY

et al. 2012

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“…Covariance processing is another option but is occasionally prone to artifact. [21][22][23][24][25] Despite all these measures, often the desired separation of peaks is not achieved. Pure-shift based experiments such as 2D 1 H-1 H F 1 -PSYCHE-TOCSY that replaces the broad multiplets by singlets in the indirect ( F 1 ) dimension have the potential to resolve the spectral complexity.…”

Section: Introductionmentioning

confidence: 99%

Identification of metabolites in coriander seeds (Coriandrum Sativum L.) aided by ultrahigh resolution total correlation NMR spectroscopy

Verma

Parihar

Baishya

2019

Magnetic Reson in Chemistry

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NMR is a fast method for obtaining a holistic snapshot of the metabolome and also offers quantitative information without separating the compounds present in a complex mixture. Identification of the metabolites present in a plant extract sample is a crucial step for all plant metabolomics studies. In the present work, we used various two dimensional (2D) NMR methods such as J‐resolved NMR, total correlation spectroscopy (TOCSY), and heteronuclear single quantum coherence sensitivity enhanced NMR spectroscopy for the identification of 36 common metabolites present in Coriandrum sativum L. seed extract. The identified metabolites belong to the following classes: organic acids, amino acids, and carbohydrates. 1H NMR spectra of such complex mixtures in general display tremendous signal overlap due to the presence of a large number of metabolites with closely resonating multiplet signals. This signal overlapping leads to ambiguity in an assignment, and hence, identification of metabolites becomes tedious or impossible in many cases. Therefore, the utility of pure‐shift proton spectrum along the indirect (F1) dimension of the F1‐PSYCHE‐TOCSY spectrum is demonstrated for overcoming ambiguity in assignment of metabolites in crowded spectral regions from Coriandrum sativum L. seed extract sample. Because pure‐shift NMR methods yield ultrahigh resolution spectrum (i.e., a singlet peak per chemical site) along one or more dimensions, such spectra provide better identification of metabolites compared with regular 2D TOCSY where signal overlap and peak distortions lead to ambiguity in the assignment. Nine metabolites were unambiguously assigned by pure‐shift F1‐PSYCHE‐TOCSY spectrum, which was unresolved in regular TOCSY spectrum.

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“…Out of the manifold of variations to combine raw and Fourier transformed data, a variety of covariance-transformed spectral representations have been introduced and their applications have been demonstrated: Among those used in NMR spectroscopy, the most often used or described were direct covariance, indirect covariance, doubly indirect covariance, unsymmetrical indirect covariance, generalized indirect covariance, which replaced the previous one, multidimensional covariance in form of Triple-Rank Covariance and 4D Covariance [2,[26][27][28][29]. Furthermore, the family of Statistical Correlation Spectroscopy (STOCSY) has been introduced, and its usefulness is demonstrated in many applications [22,[30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Homo- and Hetero-Covariance NMR Spectroscopy and Applications to Process Analytical Technology

Jaeger¹,

Legner²

2017

Spectroscopic Analyses - Developments and Applications

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Covariance processing of data and spectra has established itself among the computerbased NMR spectroscopy methodologies to increase sensitivity and resolution and to facilitate spectral analysis. While homo-correlations yield two-dimensional (2D) diagonally symmetric or antisymmetric spectra, hetero-covariance transformations allow to transfer NMR chemical shift information to other spectroscopic techniques, such as near infra-red or Raman. This is visualized as a 2D correlation map, provided a common indirect or perturbation domain, such as time, concentration change, and pressure. Covariance spectra can be generated as synchronous or asynchronous maps. The synchronous map relates the signals of species, e.g., educts and products. The asynchronous spectrum allows to derive the sequential order in which such species occur relative to each other. After a theoretical introduction into covariance NMR, its application in process analytical technology is discussed for wine fermentation, a radical polymerization reaction, a continuous process ethanol production using immobilized yeast, and a Knoevenagel condensation in a microreaction system. The covariance approach is extended toward two perturbation variables and quantitative relationships through PARAFAC kernel analysis and is illustrated for the preparation of polylactic acid nanocomposites. The advantages and added values of using synchronous and asynchronous spectra to gain process knowledge and control are demonstrated.

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Using indirect covariance processing for structure elucidation of small molecules in cases of spectral crowding

Cited by 19 publications

References 66 publications

Decoupling Two‐Dimensional NMR Spectroscopy in Both Dimensions: Pure Shift NOESY and COSY

Decoupling Two‐Dimensional NMR Spectroscopy in Both Dimensions: Pure Shift NOESY and COSY

Identification of metabolites in coriander seeds (Coriandrum Sativum L.) aided by ultrahigh resolution total correlation NMR spectroscopy

Homo- and Hetero-Covariance NMR Spectroscopy and Applications to Process Analytical Technology

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