Abstract
► Capsular polysaccharides for vaccines – physical properties crucial. ► 10 serotypes of Streptococcus pneumoniae: heterogeneity and conformation. ► Independent methods, AUC and light scattering, viscosity, chromatography. ► Unimodal distributions with wide range of average molecular weights. ► HYDFIT and other analyses show semi-flexible, persistence lengths 4–9nm.
Capsular polysaccharides from ten different serotypes of Streptococcus pneumoniae have been studied with regards their hydrodynamic properties in solution, namely their sedimentation coefficient and molar mass distributions, solution conformations and flexibilities (persistence lengths Lp), important properties for the construction of polysaccharide and glycoconjugate vaccines. Sedimentation and molar mass distributions (obtained by sedimentation velocity and equilibrium analysis in the analytical ultracentrifuge supported by size exclusion chromatography coupled to multi-angle light scattering measurements) were generally unimodal, with weight (mass) average molar masses ranging from 100×103 to 1300×103g/mol. Estimates of chain flexibilities from three different procedures applied to intrinsic viscosity, sedimentation coefficient and molar mass data, showed that the polysaccharides from all the serotypes studied had semi-flexible structures in solution with persistence lengths in the range from ∼4 to 9nm.