Elucidation of the structure of the lipopolysaccharide core and the linkage between the core and the O-antigen in Pseudomonas aeruginosa immunotype 5 using strong alkaline degradation of the lipopolysaccharide

The products of the strong alkaline degradation of the lipopolysaccharide (LPS) of Pseudomonas aeruginosa immunotype 5 were separated by anion-exchange HPLC and studied by electrospray ionization mass spectrometry and NMR spectroscopy.It was found that two major products have the same inner core region and lipid A carbohydrate backbone but different outer core regions.The difference is in the position of a rhamnose residue,which is substituted with either an additional glucose residue or a disaccharide remainder of the degraded O-polysaccharide.The site and the configuration of the linkage between the O-polysaccharide and the core were determined and,together with published data,the structure of the so-called biological repeating unit of the O-antigen was defined.The glycosidic linkage of the 2-acetamido-2,6-dideoxy D-glucose (N-acetyl-D-quinovosamine) residue is when it links the O-polysaccharide to the core and when it connects the interior repeating units of the O-polysaccharide to each other.