The chemical structure of the core oligosaccharide of the lipopolysaccharide isolated from Escherichia coli rough mutant F653, representing the enterobacterial R3 core type, was investigated by quantitative and methylation analyses, nuclear magnetic resonance spectroscopy, gas-liquid chromatography/mass spectrometry, and determined as

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All sugars are present as α-pyranosides but the anomeric configurations of the 3-deoxy-D-manno-octulopyranosonic acid (Kdo) residues could not be determined. The third Kdo and the heptose-linked GlcN residue are present in nonstoichiometric amounts; the GlcN residues may be, at least partially, N-acetylated.