title: Conformational preferences of the O-antigen polysaccharides of Escherichia coli O5ac and O5ab using NMR spectroscopy and molecular modeling.
abstract: 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.
authors.affiliation: Centre de Recherches sur les Macromolécules Végétales-CNRS, affiliated with Université Grenoble and ICMG, BP 53 X, 38041 Grenoble Cedex, France.
authors.forename: Anita
authors.initials: A
authors.lastname: Sarkar
authors.forename: Carolina
authors.initials: C
authors.lastname: Fontana
authors.forename: Anne
authors.initials: A
authors.lastname: Imberty
authors.forename: Serge
authors.initials: S
authors.lastname: Pérez
authors.forename: Göran
authors.initials: G
authors.lastname: Widmalm
mesh_terms: D000465:Algorithms; D002236:Carbohydrate Conformation; D004926:Escherichia coli / Q000276:immunology*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D019081:O Antigens / Q000737:chemistry*
chemical_list: D019081:O Antigens