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Suppressing one-bond homonuclear 13C,13C scalar couplings in the J-HMBC NMR experiment: application to 13C site-specifically labeled oligosaccharides
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2014 (English)In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 52, no 3, 82-86 p.Article in journal (Refereed) Published
Abstract [en]

Site-specific C-13 isotope labeling is a useful approach that allows for the measurement of homonuclear C-13,C-13 coupling constants. For three site-specifically labeled oligosaccharides, it is demonstrated that using the J-HMBC experiment for measuring heteronuclear long-range coupling constants is problematical for the carbons adjacent to the spin label. By incorporating either a selective inversion pulse or a constant-time element in the pulse sequence, the interference from one-bond C-13,C-13 scalar couplings is suppressed, allowing the coupling constants of interest to be measured without complications. Experimental spectra are compared with spectra of a nonlabeled compound as well as with simulated spectra. The work extends the use of the J-HMBC experiments to site-specifically labeled molecules, thereby increasing the number of coupling constants that can be obtained from a single preparation of a molecule.

Place, publisher, year, edition, pages
2014. Vol. 52, no 3, 82-86 p.
Keyword [en]
NMR, 1H, 13C, J-HMBC, oligosaccharide, heteronuclear long-range coupling constants, site-specific labeling
National Category
Chemical Sciences Physical Chemistry Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-101733DOI: 10.1002/mrc.4038ISI: 000330951600003OAI: oai:DiVA.org:su-101733DiVA: diva2:705666
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

AuthorCount:3;

Available from: 2014-03-17 Created: 2014-03-14 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Conformations of Flexible Oligosaccharides: Molecular Simulations and NMR spectroscopy
Open this publication in new window or tab >>Conformations of Flexible Oligosaccharides: Molecular Simulations and NMR spectroscopy
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The conformational preferences of several oligosaccharides are investigated herein using a combination of NMR spectroscopy and molecular dynamics (MD) simulations, focusing on the torsion angles associated with the glycosidic linkages.

Strategies for obtaining usable J-HMBC spectra for carbons with an adjacent 13C label are described. By employing a selective pulse or a constant time modification, spectra free from interferences are obtained for site-specifically 13C labeled oligosaccharides.

Intermolecular hydrogen bonding in sucrose is investigated using MD simulations performed at different concentrations. One of the most frequent intermolecular hydrogen bonds in the simulations, O3f∙∙∙HO3g, was detected using the HSQC-TOCSY NMR experiment.

Based on MD simulations and NMR spectroscopy, the conformational ensemble for a trisaccharide segment of the LeaLex hexasaccharide is proposed to feature conformational exchange between conformations with positive and negative values for the ψ3 torsion angle in the β-D-GlcpNAc-(1→3)-β-D-Galp linkage.

Using MD simulations, the conformation of the N-acetyl group is shown to influence the glycosidic conformation at a nearby linkage in two oligosaccharides.

Short (1→6)-linked oligosaccharides are shown to exhibit conformational exchange at the ω and ψ torsion angles. Notably, the former torsion angle populates states with ψ ≈ ±90°. Conformationally sensitive homo- and heteronuclear coupling constants are determined using various NMR experiments. The experimental data, including effective distances from NOESY obtained for two of the compounds, is used to improve the representation of the ω torsion angle in the CHARMM36 force field.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2013. 78 p.
Keyword
Carbohydrates, Oligosaccharide, Conformation, NMR spectroscopy, MD simulations
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-95480 (URN)978-91-7447-808-2 (ISBN)
Public defence
2013-12-13, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 5: Accepted. Paper 6: Manuscript.

Available from: 2013-11-21 Created: 2013-10-29 Last updated: 2015-10-06Bibliographically approved

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