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Conformational Preferences of the O-Antigen Polysaccharides of Escherichia coli O5ac and O5ab Using NMR Spectroscopy and Molecular Modeling
Stockholm University, Faculty of Science, Department of Organic Chemistry.
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2013 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, no 7, p. 2215-2224Article in journal (Refereed) Published
Abstract [en]

Escherichia coli serogroup O5 comprises two different subgroups (O5ab and O5ac), which are indiscernible from the point of view of standard immunological serotyping. The structural similarities between the O-antigen polysaccharides (PSs) of these two strains are remarkable, with the only difference being the glycosidic linkage connecting the biological tetrasaccharide repeating units. In the present study, a combination of NMR spectroscopy and molecular modeling methods were used to elucidate the conformational preferences of these two PSs. The NMR study was based on the analysis of intra- and inter-residue proton-proton distances using NOE build-up curves. Molecular models of the repeating units and their extension to polysaccharides were obtained, taking into account the conformational flexibility as assessed by the force field applied and a genetic algorithm. The agreements between experimentally measured and calculated distances could only be obtained by considering an averaging of several low energy conformations observed in the molecular models.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2013. Vol. 14, no 7, p. 2215-2224
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-92630DOI: 10.1021/bm400354yISI: 000321793700011OAI: oai:DiVA.org:su-92630DiVA, id: diva2:641748
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationEU, FP7, Seventh Framework Programme
Note

AuthorCount:5;

Available from: 2013-08-19 Created: 2013-08-14 Last updated: 2022-02-24Bibliographically approved
In thesis
1. NMR spectroscopy in structural and conformational analysis of bacterial polysaccharides
Open this publication in new window or tab >>NMR spectroscopy in structural and conformational analysis of bacterial polysaccharides
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Carbohydrates constitute one of the three major classes of biomolecules found in all living cells and, unlike nucleic acids and proteins, their polymeric structures are not based on a template. The structural diversity of these molecules confers them an enormous capacity to encode information in biological systems, acting as efficient mediators in the interaction of the cell with the environment. In order to understand the roles of glycans in biological processes it is of key importance to have a detailed understanding of their structures and conformational preferences, and NMR spectroscopy is one of most powerful techniques for the study of these molecules in solution.

This thesis is focused on the structural and conformational analysis of lipopolysaccharides from Gram-negative bacteria. In the first two projects (Chapter 2 and 3) the structural analyses of the biological repeating units of the O-antigen polysaccharides from E. coli O174ab and O115 are described; in both cases a combination of NMR spectroscopy and gas chromatography techniques were used. Special emphasis was made in the characterization of the O-acetylation patterns observed in the native O-antigen polysaccharide from E. coli O115. Chapter 4 describes the development of a new methodology for the determination of the absolute configuration of monosaccharide components of glycans. This methodology was used in the structural elucidation of the O-antigen PS of E. coli O155 (Chapter 5) that was carried out in a semi-automated manner using the program CASPER and unassigned NMR data. The conformational preferences of O-antigen PS of E. coli O5ac and O5ab are analyzed in Chapter 6, using a combination of NMR spectroscopy and molecular modeling methods. In Chapter 7 the structural analysis is focused on the core region of the LPS, and the structures of the deacylated lipooligosaccharides of three rough mutants of B. melitesis are reported. In several of the aforementioned chapters, the biosynthetic aspects behind the assembly of the respective PSs were examined on the bases of genetic information available in the NCBI and ECODAB databases.  Finally, in Chapter 8, different NMR pulse sequences available for the study of proteins and nucleic acids were evaluated and optimized for the structural analysis of 13C uniformly-labeled oligo- and polysaccharides.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2013. p. 83
Keywords
Nuclear Magnetic Resonance, carbohydrates, O-antigen polysaccharide
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-93833 (URN)978-91-7447-758-0 (ISBN)
Public defence
2013-10-18, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 215536
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 6: Manuscript. Paper 7: Manuscript.

Available from: 2013-09-26 Created: 2013-09-17 Last updated: 2022-02-24Bibliographically approved

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