H. Masoud et al., STRUCTURAL ELUCIDATION OF THE BACKBONE OLIGOSACCHARIDE FROM THE LIPOPOLYSACCHARIDE OF MORAXELLA-CATARRHALIS SEROTYPE-A, Canadian journal of chemistry, 72(6), 1994, pp. 1466-1477
The cell-surface lipopolysaccharide produced by Moraxella catarrhalis
serotype A is composed of a hydrophobic lipid A moiety and an oligosac
charide, but lacks high-molecular-weight O-polysaccharide chains. The
oligosaccharide component is composed of D-glucose, D-galactose, D-glu
cosamine, and 3-deoxy-D-manno-octulosonic acid. The carbohydrate backb
one was obtained from the lipopolysaccharide by employing a reaction s
equence involving deacylation, dephosphorylation, and reduction of the
reducing D-glucosamine terminus of the lipid A moiety. Structural ana
lysis of the backbone oligosaccharide employed a combination of microa
nalytical methods and nuclear magnetic resonance spectroscopy. Homo- a
nd hetero-nuclear chemical shift correlation techniques and nuclear Ov
erhauser enhancement (NOE) experiments led to the unambiguous assignme
nt of the H-1 and C-13 resonances associated with each of the componen
t glycosyl residues and established their sequence within the backbone
oligosaccharide as shown, [GRAPHICS] This lipopolysaccharide was foun
d to consist of a highly branched, D-glucose-containing inner-core reg
ion which possesses a unique and unusual solution conformation. This w
as established by measurement of transglycosidic NOEs and three-bond H
-1-C-13 coupling constants, in conjunction with molecular modeling. A
D-galactose-containing disaccharide identified as a terminal group of
the lipopolysaccharide was structurally identical to antigenic epitope
s expressed by certain mammalian epithelial cells and may be related t
o the virulence potential of this human pathogen.