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1. (Article ID: 1051)
 
Niggemann J, Kamerling JP, Vliegenthart JFG
Application of β-1,4-galactosyltransferase in the synthesis of complex branched-chain oligosaccharide mimics of fragments of the capsular polysaccharide of Streptococcus pneumoniae type 14
Journal of the Chemical Society, Perkin Transactions 1 (18) (1998) 3011-3020
 

The chemoenzymic synthesis is described of b-D-Galp-(1-4)-b-D-Glcp-(1-6)-[b-D-Galp-(1-4)]-b-DGlcpNAc-(1-O[CH2]3O-4)-b-D-Glcp-(1-OCH2CH=CH2) 32 and b-D-Galp-(1-4)-b-D-GlcpNAc-(1-O[CH2]3O-4)-b-D-Glcp-(1-6)-[b-D-Galp-(1-4)]-b-D-GlcpNAc-(1-O[CH2]3O-4)-b-D-Glcp-(1-OCH2-CH=CH2) 33, representing hexa- and octasaccharide mimics of fragments of the Streptococcus pneumoniae type 14 polysaccharide. In a chemical approach the intermediate linear oligosaccharide mimics 30 and 31 were synthesized, wherein both terminal and non-terminal N-acetyl-b-D-glucosamine residues were not yet galactosylated. The alkyl-bridged derivatives were found to be good acceptor substrates for bovine milk b-1,4-galactosyltransferase. Reaction of the anomeric allyl functions with cysteamine under UV-irradiation gave the corresponding 3-(2-aminoethylthio)propyl glycosides 34 and 35, suitable for further coupling of the oligosaccharide mimics to protein carriers.

synthesis, Streptococcus pneumoniae, capsular polysaccharide

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2. (Article ID: 1369)
 
Baxa U, Steinbacher S, Miller S, Weintraub A, Huber R, Seckler R
Interactions of phage P22 tails with their cellular receptor, Salmonella O-antigen polysaccharide
Biophysical Journal 71 (1996) 2040-2048
 

Bacteriophage P22 binds to its cell surface receptor, the repetitive O-antigen structure in Salmonella lipopolysaccharide, by its six homotrimeric tailspikes. Receptor binding by soluble tailspikes and the receptor-inactivating endorhamnosidase activity of the tailspike protein were studied using octa- and dodecasaccharides comprising two and three O-antigen repeats of Salmonella enteritidis and Salmonella typhimurium lipopolysaccharides. Wild-type tailspike protein and three mutants (D392N, D395N, and E359Q) with defective endorhamnosidase activity were used. Oligosaccharide binding to all three subunits, measured by a tryptophan fluorescence quench or by fluorescence depolarization of a coumarin label attached to the reducing end of the dodecasaccharide, occurs independently. At 10 degrees C, the binding affinities of all four proteins to oligosaccharides from both bacterial strains are identical within experimental error, and the binding constants for octa- and dodecasaccharides are 1 x 10(6) M(-1) and 2 x 10(6) M(-1), proving that two O-antigen repeats are sufficient for lipopolysaccharide recognition by the tailspike. Equilibration with the oligosaccharides occurs rapidly, but the endorhamnosidase produces only one cleavage every 100 s at 10 degrees C or about 2 min(-1) at the bacterial growth temperature. Thus, movement of virions in the lipopolysaccharide layer before DNA injection may involve the release and rebinding of individual tailspikes rather than hydrolysis of the O-antigen.

polysaccharide, O-antigen, O antigen, Salmonella, interaction, cellular, receptor, phage

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