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Carbohydr Res. 2018 Jul 30;465:1-3. doi: 10.1016/j.carres.2018.05.006. Epub 2018 May 19.

Structural studies on the O-polysaccharide of Escherichia coli O57.

Author information

1
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47, Leninsky Prosp., 119991 Moscow, Russian Federation; Higher Chemical College of the Russian Academy of Sciences, D. I. Mendeleev University of Chemical Technology of Russia, Moscow, Russian Federation.
2
Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin 300457, PR China.
3
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47, Leninsky Prosp., 119991 Moscow, Russian Federation.
4
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47, Leninsky Prosp., 119991 Moscow, Russian Federation. Electronic address: andreivperepelov@gmail.com.

Abstract

Mild acid hydrolysis of the lipopolysaccharide of Escherichia coli O57 afforded an O-polysaccharide, which was isolated by gel permeation chromatography (GPC) and studied by sugar analysis, Smith degradation and solvolysis with trifluoroacetic acid, along with 2D 1H and 13C NMR spectroscopy. The O-polysaccharide was found to contain d-Glc, d-Gal, d-GalA, d-GlcNAc, and l-FucNAc, as well as O-acetyl groups. Smith degradation of the O-deacetylated polysaccharide destroyed side-branch β-Glсp and α-GalpA to give a modified linear polysaccharide. Solvolysis cleaved selectively the linkage of α-l-FucpNAc to give a pentasaccharide corresponding to the O-polysaccharide repeat. A comparison of the NMR spectra of the initial and O-deacetylated polysaccharides showed that α-GalpA is non-stoichiometrically O-acetylated at position either 2 (∼30%) or 3 (∼40%). The following structure of the O-polysaccharide was established, which is unique among known bacterial polysaccharide structures.

KEYWORDS:

Bacterial polysaccharide structure; CF(3)CO(2)H solvolysis; Escherichia coli; O-antigen; O-polysaccharide

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