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Conformation and Dynamics at a Flexible Glycosidic Linkage Revealed by NMR Spectroscopy and Molecular Dynamics Simulations: Analysis of β-ʟ-Fucp-(1→6)-α-ᴅ-Glcp-OMe in Water Solution
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.
2013 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, no 47, 14709-14722 p.Article in journal (Refereed) Published
Abstract [en]

The intrinsic flexibility of carbohydrates facilitates different 3D structures in response to altered environments. At glycosidic (1 -> 46)-linkages, three torsion angles are variable, and herein the conformation and dynamics of beta-1.-Fucp-(1 -> 6)-alpha-D-Glcp-OMe are investigated using a combination of NMR spectroscopy and molecular dynamics (MD) simulations. The disaccharide shows evidence of conformational averaging for the psi and co torsion angles, best explained by a four-state conformational distribution. Notably, there is a significant population of conformations having psi = 85 degrees (clinal) in addition to those having psi = 180 degrees (anfiperiplanar). Moderate differences in C-13 R-1 relaxation rates are found to be best explained by axially symmetric tumbling in combination with minor differences in librational motion for the two residues, whereas the isomerization motions are occurring too slowly to significantly to the observed relaxation rates. The MD simulation was found to give a reasonably good agreement with experiment, especially with respect to diffusive properties, among which the rotational anisotropy, D parallel to/D parallel to, is found to be 2.35. The force field employed showed too narrow omega torsion angles in the gauche trans and gauche gauche states as well as overestimating the population of the gauche trans conformer. This information can subsequently be used in directing parameter developments and emphasizes the need for refinement of force fields for (1 -> 6)-linked carbohydrates.

Place, publisher, year, edition, pages
2013. Vol. 117, no 47, 14709-14722 p.
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-100876DOI: 10.1021/jp409985hISI: 000330160100013OAI: oai:DiVA.org:su-100876DiVA: diva2:697467
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

AuthorCount:3;

Available from: 2014-02-18 Created: 2014-02-17 Last updated: 2017-12-06Bibliographically 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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