Structure of the O-polysaccharide of Providencia alcalifaciens O25 containing an amide of D-galacturonic acid with N^ε-[(R)-1-carboxyethyl]-L-lysine

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N. A. Kocharova¹, O. G. Ovchinnikova^1*, M. Bialczak-Kokot², A. S. Shashkov¹, Y. A. Knirel¹, and A. Rozalski²

¹Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky pr. 47, 119991 Moscow, Russia; fax: (499) 137-6148; E-mail: olga.ovchinnikova@gmail.com

²Department of Immunobiology of Bacteria, Institute of Microbiology, Biotechnology, and Immunology, University of Lodz, PL 90-237 Lodz, Poland

^* To whom correspondence should be addressed.

Received January 18, 2011; Revision received February 3, 2011

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An acidic O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Providencia alcalifaciens O25 followed by gel-permeation and anion-exchange chromatography. The O-polysaccharide was studied by sugar and methylation analyses along with ¹H and ¹³C NMR spectroscopy, including two-dimensional correlation ¹H,¹³C HMBC, and ¹H,¹H ROESY experiments both in D₂O and, to detect correlations for NH protons, in a 9 : 1 H₂O/D₂O mixture. An amino acid was isolated from the polysaccharide by acid hydrolysis and identified as N^ε-[(R)-1-carboxyethyl]-L-lysine (“alaninolysine”, 2S,8R-alaLys) by determination of the specific optical rotation and ¹³C NMR spectroscopy, using the authentic synthetic diastereomers 2S,8R-alaLys and 2S,8S-alaLys for comparison. The structure of the branched tetrasaccharide repeating unit of the O-polysaccharide was established.

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KEY WORDS: Providencia alcalifaciens, O-antigen, lipopolysaccharide, bacterial polysaccharide structure, opine, N^ε-[(R)-1-carboxyethyl]-L-lysine

DOI: 10.1134/S0006297911060125

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