1H-Detected IPAP DEPT-INADEQUATE and IPAP RINEPT-INADEQUATE for the measurement of long-range carbon–carbon coupling constants

Jin, Lan; Kövér, Katalin E.; Lenoir, Marc; Uhrı́n, Dušan

doi:10.1016/j.jmr.2007.10.016

Cited by 17 publications

(13 citation statements)

References 39 publications

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“…They are attainable by e.g. 1 H-detected IPAP DEPT-INADEQUATE experiments 37 , albeit at long acquisition times with high concentrations of compounds. Alternatively, isotopologues, 13 C-labeled at the anomeric carbon and at the glycosyloxylated carbon atom, 14 i.e., the carbon at the linkage position of a glycosidic linkage, efficiently results in six transglycosidic J couplings, viz., 3 J H1',Cn , 3 J C1',Hn , 3 J C2',Cn , 3 J C1',C(n−1) , 3 J C1',C(n+1) , and 2 J C1',Cn , where n is the substitution position, although this requires synthesis of the site-specifically labeled oligosaccharide.…”

Section: Resultsmentioning

confidence: 99%

“…The five trisaccharides were previously analyzed to different extents using molecular mechanics conformational searches, Monte Carlo or molecular dynamics simulations in conjunction with NMR spectroscopy experiments. 21–26 However, further improvements in understanding the conformational properties of these saccharides can be attained due to the advent of improved force fields for carbohydrates, 27–33 computational enhanced sampling techniques 34–36 and novel NMR experiments 37, 38 in conjunction with further developed Karplus-type relationships 39 that allow for interpretation of transglycosidic heteronuclear 3 J CH coupling constants and of homonuclear 3 J CC couplings. To this end, site-specifically 13 C-labeled versions of compound 3 were synthesized, namely isotopologues having carbon-13 atoms at C1 or C2 of the glucopyranosyl residues thereby facilitating determination of long-range n J CC across the glycosidic linkages related to both the ϕ and ψ torsion angles.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Delineating the conformational flexibility of trisaccharides from NMR spectroscopy experiments and computer simulations

Yang

d’Ortoli

Säwén

et al. 2016

Phys. Chem. Chem. Phys.

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The conformation of saccharides in solution is challenging to characterize in the context of a single well-defined three-dimensional structure. Instead, they are better represented by an ensemble of conformations associated with their structural diversity and flexibility. In this study, we delineate the conformational heterogeneity of five trisaccharides via a combination of experimental and computational techniques. Experimental NMR measurements target conformationally sensitive parameters, including J couplings and effective distances around the glycosidic linkages, while the computational simulations apply the well-calibrated additive CHARMM carbohydrate force field in combination with efficient enhanced sampling molecular dynamics simulation methods. Analysis of conformational heterogeneity is performed based on sampling of discreet states as defined by dihedral angles, on root-mean-square differences of Cartesian coordinates and on the extent of volume sampled. Conformational clustering, based on the glycosidic linkage dihedral angles, shows that accounting for the full range of sampled conformations is required to reproduce the experimental data, emphasizing the utility of the molecular simulations in obtaining an atomic detailed description of the conformational properties of the saccharides. Results show the presence of differential conformational preferences as a function of primary sequence and glycosidic linkage types. Significant differences in conformational ensembles associated with the anomeric configuration of a single glycosidic linkage reinforce the impact of such changes on the conformational properties of carbohydrates. The present structural insights of the studied trisaccharides represent a foundation for understanding the range of conformations adopted in larger oligosaccharides and how these molecules encode their conformational heterogeneity into the monosaccharide sequence.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Delineating the conformational flexibility of trisaccharides from NMR spectroscopy experiments and computer simulations

Yang

d’Ortoli

Säwén

et al. 2016

Phys. Chem. Chem. Phys.

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“…The INADEQUATE experiment1–4 is potentially a very powerful experiment for structure determination in organic molecules 5–13. It can explicitly map out the carbon–carbon connectivity of a molecule, using the scalar coupling between two 13 C nuclei.…”

Section: Introductionmentioning

confidence: 99%

Problems, artifacts and solutions in the INADEQUATE NMR experiment

Bain

Hughes

Anand

et al. 2010

Magnetic Reson in Chemistry

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The INADEQUATE experiment can provide unequalled, detailed information about the carbon skeleton of an organic molecule. However, it also has the reputation of requiring unreasonable amounts of sample. Modern spectrometers and probes have mitigated this problem, and it is now possible to get good structural data on a few milligrams of a typical organic small molecule. In this paper, we analyze the experiment step by step in some detail, to show how each part of the sequence can both contribute to maximum overall sensitivity and can lead to artifacts. We illustrate these methods on three molecules: 1-octanol, the steroid 17α-ethynylestradiol and the isoquinoline alkaloid β-hydrastine. In particular, we show that not only is the standard experiment powerful, but also a version tuned to small couplings can contribute vital structural information on long-range connectivities. If the delay in the spin echo is long, pairs of carbons with small couplings can create significant double-quantum coherence and show correlations in the spectrum. These are two-and three-bond correlations in a carbon chain or through a heteroatom in the molecule. All these mean that INADEQUATE can play a viable and important role in routine organic structure determination.

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“…in a form of INADEQUATE composite refocusing (CR) and most notably by hydrogen detection . These new sequences were modified for detection of magnitudes of carbon–carbon coupling constants, but none of them is able to detect the signs of these couplings. Of the modern methods, only sign labeled polarization transfer (SLAP) pulse sequence is capable of broadband detection of signed carbon–carbon couplings in samples with natural 13 C abundance.…”

Section: Introductionmentioning

confidence: 99%

HCSE method for detection of small carbon–carbon couplings and their signs, comparison with SLAP pulse sequence

Blechta

Schraml

2013

Magnetic Reson in Chemistry

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Performance of homonuclear coupling sign edited (HCSE) experiment applied to detection of signed carbon-carbon couplings is discussed using a set of already measured samples of nine monosubstituted benzenes. It is shown that coupling sign detection is insensitive to the settings of carbon-carbon polarization transfer delays. The HCSE spectra of ten from the total of 43 measured carbon-carbon couplings were considerably influenced by relaxations and proton-proton strong couplings. These effects are quantitatively discussed. The results of HCSE and SLAP experiments are compared. It is shown that the two methods may complement each other in detection of signed carbon-carbon couplings.

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1H-Detected IPAP DEPT-INADEQUATE and IPAP RINEPT-INADEQUATE for the measurement of long-range carbon–carbon coupling constants

Cited by 17 publications

References 39 publications

Delineating the conformational flexibility of trisaccharides from NMR spectroscopy experiments and computer simulations

Delineating the conformational flexibility of trisaccharides from NMR spectroscopy experiments and computer simulations

Problems, artifacts and solutions in the INADEQUATE NMR experiment

HCSE method for detection of small carbon–carbon couplings and their signs, comparison with SLAP pulse sequence

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