Foschiatti Michela, Hearshaw Meredith, Cescutti Paola, Ravenscroft Neil, Rizzo R
Department of Life Sciences, University of Trieste, Bldg C11, Via Licio Giorgieri 1, 34127 Trieste, Italy.
Carbohydr Res. 2009 May 12;344(7):940-3. doi: 10.1016/j.carres.2009.02.027. Epub 2009 Mar 4.
The effect of different cations on the conformational and morphological properties of the capsular polysaccharide produced by Neisseria meningitidis group A was investigated. Circular dichroism studies showed that the presence of Na(+), NH4+ or Ca(2+) ions induced different local conformations of the polysaccharide chain through interactions with the phosphodiester group bridging the saccharide residues in the polymer chain. Atomic force microscopy experiments confirmed that the morphology of the polysaccharide chains was different depending on the nature of the counterion. Ammonium ions were associated with the presence of single polymer chains in an elongated conformation, whereas sodium ions favored the folding of the chains into a globular conformation. The addition of calcium ions produced the aggregation of a limited number of globular polysaccharide chains to form a 'toroidal-like' structure.
