A further 20 monosaccharide and oligosaccharide intermediates of Vibrio cholera antigens, for the preparation of a hexasaccharide-protein conjugate have been analyzed by high-resolution one-dimensional (1D) 1H and 1D 13C NMR at 500 MHz and 126 MHz, respectively. Validation of the chemical structures was based on integration of the 1D 1H NMR spectra, and on counting of carbon resonances in the 13C spectra, especially in the well-separated spectral regions of the C=O, aromatic C, C-1, C-N, and C-CH3 moieties. The NMR spectra were also used to assess the purity of the synthetic preparations, for example, determination of the extent of completion of hydrogenolytic removal of benzyl protecting groups by measurement of the content of aromatic groups. NMR spectra measured at 500 MHz have been provided for the identification of six polysaccharide fragments isolated from the lipopolysaccharide of Shigella flexneri type 2a, and seven polysaccharide fractions prepared from a mutant version of this bacterium. Comparison of the integrals of the polysaccharide H-1 and rhamnose methyl signals facilitated detection of core polysaccharide in the samples. The techniques provide complex fingerprint spectra that can be compared with literature data to verify identity. A new preparation of the capsular polysaccharide of Haemophilus influenzae type a has been investigated by 1D 1H and 13C NMR and found to have excellent purity, and close agreement with the spectra of previous preparations in this laboratory. These spectra had been analyzed several years ago by two-dimensional NMR methods to give sets of 1H-1H and C-1,H-1 coupling constants for the D-glucose residue and 13C-31P coupling constants for the D-glucose and D-ribitol components of the polysaccharide. Also obtained, were complete assignments of the 1H and 13C NMR signals of the beta-D-glucopyranosyl and D-ribitol residues, which are joined by a phosphoric diester linkage between O-4 of the D-glucose and O-5 of the D-ribitol.
| Kubler-Kielb, Joanna; Vinogradov, Evgeny; Mocca, Christopher et al. (2010) Immunochemical studies of Shigella flexneri 2a and 6, and Shigella dysenteriae type 1 O-specific polysaccharide-core fragments and their protein conjugates as vaccine candidates. Carbohydr Res 345:1600-8 |
