Complete NMR structural elucidation of the capsular polysaccharide adjuvant from Klebsiella I-714
Adam, O.; Riviére, M.; Vercellone, A.; Monsan, P.F.; Puzo, G.
European Journal of Biochemistry 241(2): 602-610
ISSN/ISBN: 0014-2956 PMID: 8917462 DOI: 10.1111/j.1432-1033.1996.00602.x
The capsular polysaccharide (CPS) produced by the non-pathogenic Klebsiella strain I-714, selected for its immunomodulating activity, has been purified and almost completely detoxified in a previous study (Adam, O., Vercellone, A., Paul, F., Monsan, R F. and Puzo, G. (1995) Anal. Biochem. 225, 321-3271. The present report concerns the structural elucidation of this CPS by several one-dimensional and two-dimensional 1H-NMR and 13C-NMR experiments performed on the native molecule. It was found to be a high molecular-mass branched polymer constituted by a hexasaccharide repeating unit of following structure: 4)-alpha-L-Rhap-(1 fwdarw 3)-beta-D-Galp-(1 fwdarw 2)-alpha-L-Rhap-(1 fwdarw 4)-beta-D-GlcpA-(1 fwdarw )-(-alpha-L-Rhap-(1 fwdarw 2)-)-alpha-D-Galp-(1. The presence of two glycosidic substitutions on the Galp residue resulted in a strong overlapping of its proton signals, preventing direct assignment of both proton and carbon resonances. However, assignment could be achieved using the two-bond and three-bond 1H-13C heteronuclear coupling observed in the 1H-13C heteronuclear multiple-bond correlation (HMBC) spectrum.