Structure of the biological repeating unit of the O-antigen of Pseudomonas aeruginosa immunotype 4 containing both 2-acetamido-2,6-dideoxy-d-glucose and 2-acetamido-2,6-dideoxy-d-galactose

A phosphorylated core-lipid A backbone oligosaccharide that carries a disaccharide remainder of the first O-antigen repeating unit was derived by strong alkaline degradation following mild hydrazinolysis of the lipopolysaccharide of Pseudomonas aeruginosa immunotype 4 (serogroup O-1). The structure of the oligosaccharide was determined using ESI MS and NMR spectroscopy and it was demonstrated that 2-acetamido-2,6-dideoxy-d-glucose is the first monosaccharide of the O-polysaccharide that is linked to the LPS core. These data define the structure of the biological repeating unit of the O-antigen.