Phosphate localization in carbohydrates - a study on enterobacterial lipopolysaccharides.

The localization of the phosphate substituents in the core oligosaccharide of the lipopolysaccharides of Enterobacteriaceae has been reported for Salmonella minnesota and Escherichia coli B only. In these cases the localizations were done by a beta-elimination reaction in mild alkaline solution after periodate oxidation. We report now on a method generally applicable on carbohydrates. The localization of phosphate groups and the extent of substitution with phosphate residues in carbohydrates can be determined by the following reaction sequence: methylation, dephosphorylation, and reetherification (labelling) with C2H3J or C2H5J followed by derivatizing to partially methylated alditol acetates and analysis by combined gas liquid chromatography/mass spectrometry. The results presented here are obtained by application of this method to isolated core oligosaccharides of lipopolysaccharides from E. coli C23.1, E. coli C71, E. coli F2515, and P. mirabilis R4/O 28. Phosphate is localized at C-4 of the chain heptoses in the lipopolysaccharides of E. coli C and E. coli R4, and at C-7 of the branching heptose in the lipopolysaccharide of P. mirabilis R4/O 28.