title: Molecular dynamics simulations of the Salmonella typhi Vi antigenic polysaccharide and effects of the introduction of a zwitterionic motif.
abstract: A series of hexasaccharides corresponding to the Vi capsular polysaccharide, a polymer of α-(1→4)-galacturonic acid, and analogs containing a zwitterionic motif with various degrees of acetylation at positions 3 have been modeled. When submitted to molecular dynamics simulations in a water box, all the structures visited only two quite restricted regions of the φ/ψ conformational space both corresponding to extended geometries without any tendency towards supercoiling. The most stable conformation showed a clockwise helix arrangement of substituents on the molecular surface whereas the opposite arrangement was observed for the other conformation. The flexibility of the system and the hydrophobic character of the molecular surface are modulated by the 3-O-acetyl groups that confer rigidity to the system. In the zwitterionic analogs, the introduction of positive charges in the place of the acetamido groups alters the hydrophobicity that can be regained by methylation of the amino groups. The needed molecular flexibility can be obtained by the complete deacetylation at positions 3.
authors.affiliation: Dipartimento di Chimica, Università di Pavia, Via Taramelli 12, 27100 Pavia, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Legnani
authors.forename: Federica
authors.initials: F
authors.lastname: Compostella
authors.forename: Giovanni
authors.initials: G
authors.lastname: Grazioso
authors.forename: Franca Marinone
authors.initials: FM
authors.lastname: Albini
authors.forename: Lucio
authors.initials: L
authors.lastname: Toma
mesh_terms: D020816:Amino Acid Motifs; D000942:Antigens, Bacterial / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D011134:Polysaccharides / Q000737:chemistry*; D012485:Salmonella typhi
chemical_list: D000942:Antigens, Bacterial; D011134:Polysaccharides