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

N. A. Kocharova1, O. G. Ovchinnikova1*, 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
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 Nε-[(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.
KEY WORDS: Providencia alcalifaciens, O-antigen, lipopolysaccharide, bacterial polysaccharide structure, opine, Nε-[(R)-1-carboxyethyl]-L-lysine

DOI: 10.1134/S0006297911060125