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Conformational analysis of β-linked glucobiosides based on hetero- and homonuclear couplings across the glycosidic linkage
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2008 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Journal of physical chemistry, ISSN 0022-3654, Vol. 112, no 14, 4447-4453 p.Article in journal (Refereed) Published
Abstract [en]

Four β-linked glucobioses selectively 13C labeled at C1‘ or C2‘ have been prepared. The inter-residue coupling constants, JCH, and JCC, have been determined and related to the solution conformations of the disaccharides using Karplus-type relationships. Relying only on the experimental coupling constants, glycosidic linkage conformation in methyl α-sophoroside (methyl 2-O-β-d-glucopyranosyl-α-d-glucopyranoside), methyl α-laminarabioside (methyl 3-O-β-d-glucopyranosyl-α-d-glucopyranoside), and methyl α-cellobioside (methyl 4-O-β-d-glucopyranosyl-α-d-glucopyranoside) were found to be close to those observed in the solid state (39° < H < 41°, −24° < ψH < −36°). The laminarabioside and cellobioside were found to have conformations that accommodate an intramolecular hydrogen bond to O5‘ that is observed in the solid state. In all compounds, the exocyclic hydroxymethyl groups retain a conformation close to that observed in unsubstituted glucose (gt/gg 1:1). Methyl α-gentiobioside (methyl 6-O-β-d-glucopyranosyl-α-d-glucopyranoside) shows greater flexibility at the ψ-torsion than the other disaccharides, but the population distribution around the C5−C6 bond is essentially unaffected by substitution. None of the O2‘ hydroxyl groups of the β-d-glucopyranosyl residues in any of the disaccharides appear to be involved in inter-residue hydrogen bonding since 1JCH, 1JCC, and 2JCH values sensitive to C2‘−O2‘ rotamer distribution remain close to those observed in methyl β-d-glucopyranoside.

Place, publisher, year, edition, pages
2008. Vol. 112, no 14, 4447-4453 p.
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-24631DOI: 10.1021/jp710977kISI: 000254659900041OAI: oai:DiVA.org:su-24631DiVA: diva2:197973
Note
Part of urn:nbn:se:su:diva-7283Available from: 2008-01-10 Created: 2008-01-09 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Structural Studies of O-antigen polysaccharides, Synthesis of 13C-labelled Oligosaccharides and Conformational Analysis thereof, using NMR Spectroscopy
Open this publication in new window or tab >>Structural Studies of O-antigen polysaccharides, Synthesis of 13C-labelled Oligosaccharides and Conformational Analysis thereof, using NMR Spectroscopy
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In order to understand biological processes, to treat and diagnose diseases, find appropriate vaccines and to prevent the outbreak of epidemics, it is essential to obtain more knowledge about carbohydrate structures. This thesis deals with structure and conformation of carbohydrates, analysed by NMR spectroscopy and MD simulations.In the first two papers, the structures of O-antigen polysaccharides (PS) from two different E. coli bacteria were determined using NMR spectroscopy. The O-antigenic PS from E. coli O152 (paper I) consists of branched pentasaccharide repeating units, built up of three different carbohydrate residues and a phosphodiester, whilst the repeating unit of the O-antigen from E. coli O176 (paper II) is built up of a linear tetrasaccharide consisting of two different monosaccharides.

In papers III and IV, the conformational analysis of different disaccharides is described. Conformational analysis was performed using NMR spectroscopy and MD simulations (paper IV). In paper III four different glucobiosides were studied using coupling constants and Karplus-type relationships. By use of specific 13C isotopically labelled derivatives, additional coupling constants were obtained and the number of possible torsion angles was reduced by half. In paper IV, we examine the conformations of two disaccharides that are part of an epitope of malignant cells. From NOE and T-ROE experiments, short proton-proton distances around the glycosidic linkage were estimated. Furthermore, interpretation of the extracted coupling constants using Kaplus relationships gave the values of the torsion angles. As in paper III, isotopically labelled compounds were synthesised in order to enhance the sensitivity of the analysis. Finally, MD simulations were performed and the results were compared with results from NMR data.

Place, publisher, year, edition, pages
Stockholm: Institutionen för organisk kemi, 2008. 67 p.
Keyword
NMR spectroscopy, conformation, Escherichia coli, lipopolysaccharide, O-antigen, carbohydrates, structure, isotopic labelling
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-7283 (URN)978-91-7155-560-1 (ISBN)
Public defence
2008-02-08, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
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Supervisors
Available from: 2008-01-10 Created: 2008-01-09Bibliographically approved

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