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Structural determination of the O-antigenic polysaccharide from the verocytotoxin-producing Escherichia coli O176
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2008 (English)In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 343, no 4, 805-809 p.Article in journal (Refereed) Published
Abstract [en]

The structure of the O-antigen polysaccharide (PS) from Escherichia coli O176 has been determined. Component analysis together with H-1 and C-13 NMR spectroscopy was employed to elucidate the structure. Inter-residue correlations were determined by H-1,H-1 NOESY and H-1, C-13 heteronuclear multiple-bond correlation experiments. The PS is composed of tetrasaccharide repeating units with the following structure: -> 4)-alpha-D-Manp-(1 -> 2)-alpha-D-Manp-(1 -> 2)-beta-D-Manp-(1 -> 3)-alpha-D-GalpNAc-(-> Cross-peaks of low intensity from alpha-linked mannopyranosyl residues were present in the H-1, H-1 TOCSY NMR spectra and further analysis of these showed that they originate from the terminal part of the polysaccharide. Consequently, the biological repeating unit has a 3-substituted N-acetyl-D-galactosamine residue at its reducing end. The repeating unit of the E coli O176 O-antigen is similar to those from E coli 017 and 077, thereby explaining the reported cross-reactivities between the strains, and identical to that of Salmonella cerro (O:6, 14, 18).

Place, publisher, year, edition, pages
2008. Vol. 343, no 4, 805-809 p.
Keyword [en]
Escherichia coli, Salmonella cerro, Lipopolysaccharide, NMR, Biological repeating unit
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-24630DOI: 10.1016/j.carres.2008.01.003ISI: 000254720800026OAI: oai:DiVA.org:su-24630DiVA: diva2:197972
Available 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
Opponent
Supervisors
Available from: 2008-01-10 Created: 2008-01-09Bibliographically approved

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