Structure of the acidic polysaccharide chain of the lipopolysaccharide of Shewanella alga 48055

A lipopolysaccharide (LPS) with an acidic polysaccharide chain was isolated from the bacterium Shewanella alga strain 48055 and cleaved selectively at the glycosidic linkage of N-acetylneuraminic acid to give a tetrasaccharide. Studies of the tetrasaccharide and the O-deacylated LPS by 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, NOESY, rotating-frame NOE spectroscopy (ROESY), and H-detected 1H,13C heteronuclear multiple-quantum coherence (HMQC) experiments, revealed the following structure of the polysaccharide repeating unit: →3)-β-d-GalpA6GroN-(1⃗3)-β-d-GlcpNAc-(1⃗3)-α-d-GalpA6GroN-(1⃗4)-α-Neup5Ac-(2⃗ where GroN is an amidically linked residue of 2-amino-1,3-propanediol (2-amino-2-deoxyglycerol). A similar structure, but with 2-acetamido-2,6-dideoxy-d-glucose instead of 2-acetamido-2-deoxy-d-glucose, has been reported previously for the polysaccharide chain of a non-O1 Vibrio cholerae H11 LPS [E.V. Vinogradov, O. Holst, J.E. Thomas-Oates, K.W. Broady, and H. Brade, Eur. J. Biochem., 210 (1992) 491–498].