Structural elucidation of the capsular polysaccharide expressed by Escherichia coli O20:K83:H26 by high resolution NMR spectroscopy

Capsular Arabinomannans from Mycobacterium avium with Morphotype-specific Structural Differences but Identical Biological Activity

The capsules of two colony morphotypes of Mycobacterium avium strain 2151 were investigated, i.e. the virulent smooth-transparent (SmT1) and the nonvirulent smooth-opaque (SmO) types. From both morphotypes we separated a nonacylated arabinomannan (AM) from an acylated polysaccharide fraction by affinity chromatography, of which the AMs were structurally characterized. The AMs from the virulent morphotype, in contrast to that from the nonvirulent form, possessed a larger mannan chain and a shorter arabinan chain. Incubation of murine bone marrow-derived macrophages and human dendritic cells showed that the acylated polysaccharide fractions were potent inducers of tumor necrosis factor-alpha, interleukin-12, and interleukin-10 compared with nonacylated AMs, which led to only a marginal cytokine release. Further in vitro experiments showed that both the acylated polysaccharide fractions and the nonacylated AMs were able to induce in vitro anti-tumor cytotoxicity of human peripheral blood mononuclear cells. Thus, morphotype-specific structural differences in the capsular AMs of M. avium do not correlate with biological activity; however, their acylation is a prerequisite for effective stimulation of murine macrophages and human dendritic cells.

High-field NMR as a technique for the determination of polysaccharide structures

NMR spectroscopy has played a developing role in the study of polysaccharide structures for over 30 years. Many new bacterial polysaccharide repeat unit structures have recently been published as a result of the application of modern NMR techniques. NMR can also be used to elucidate the structures of both regular and heterogeneous polysaccharides from fungal and plant sources, as well as complex glycosaminoglycans of animal origin. In addition to covalent structure, conformation and dynamics of polysaccharides are susceptible to NMR analysis, both in solution and in the solid state. Improvements in NMR technology with potential applications to polysaccharide studies hold promise for the future.

Structural elucidation of the capsular polysaccharide produced by Escherichia coli O20 : K84 : H26

The primary structure of the acidic capsular antigen produced by E. coli K84 was shown by glycose and methylation analysis, and by 1D and 2D 1H and 13C NMR studies of the polysaccharide and an oligosaccharide produced by lithium-ethylenediamine degradation of the polysaccharide, to be comprised of linear hexasaccharide repeating units of the following structure: -->4)alpha-D-GaI pA-(1-->3)-alpha-D-Man p-(1-->4)-beta-D-GIc p-(1-->3)-alpha- D-Glc pNAc-(1-->2)-beta-D-Man p-(1-->3)-beta-D-Man pNAc-(1-->.