Mild alkaline degradation of the lipopolysaccharide of Escherichia coli O80 afforded a polysaccharide, which was studied by sugar analysis, selective cleavage of glycosidic linkages, and (1)H and (13)C NMR spectroscopy. Solvolysis of the polysaccharide with CF3CO2H cleaved the linkages of α-Fuc and β-linked GlcNAc and GalNAc residues to give two disaccharides. The following structure of the hexasaccharide repeating unit of the O-polysaccharide was established: The polysaccharide repeat also contains a minor O-acetyl group but its position was not determined. The O-antigen gene cluster of E. coli O80 between the conserved galF and gnd genes was analyzed and found to be consistent with the O-polysaccharide structure established.

O-antigen, Escherichia coli, O-polysaccharide, bacterial polysaccharide structure, O-antigen gene cluster

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3	bDGlcpA	104.1	74.0	76.6	72.9	77.0	?
2	Ac	175.9	23.2-23.5
	bDGlcpN	96.0	56.8	84.2	69.9	76.8	62.0


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3	bDGlcpA	4.47	3.34	3.50	3.51	3.74	-
2	Ac	-	2.02-2.03
	bDGlcpN	4.72	3.82	3.72	3.54	3.48	3.78-3.89


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3	bDGlcpA	104.1/4.47	74.0/3.34	76.6/3.50	72.9/3.51	77.0/3.74	
2	Ac		23.2-23.5/2.02-2.03
	bDGlcpN	96.0/4.72	56.8/3.82	84.2/3.72	69.9/3.54	76.8/3.48	62.0/3.78-3.89

The spectrum also has 1 signal at unknown position (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

CC(=O)N[C@H]1[C@H](O)O[C@H](CO)[C@@H](O)[C@@H]1O[C@@H]1O[C@H](C(=O)O)[C@@H](O)[C@H](O)[C@H]1O

397.333 g/mol (C₁₄H₂₃NO₁₂)