Structural Studies on the Heptose Region of Salmonella Lipopolysaccharides

Degradation studies performed on the original or dephosphorylated core oligosaccharides derived from lipopolysaccharides of Salmonella Ra, Rb, and RcP+ mutants revealed the presence of a branched heptose trisaccharide, −3(HepIII‐1,7‐)‐HepII‐1,3‐HepI–. The branching heptose III is linked to position 7 of heptose II. Heptose II is also substituted (at either position 2, 4, or 6) by a phosphate group. Other previously identified substituents of the heptose units are a pyrophosphoryl‐ethanolamine group linked to position 4 of heptose I and the hexose oligosaccharide of the core linked to position 3 of heptose II. The degree of substitution of the heptose main chain with heptose III varies in different lipopolysaccharides from 20 to 90%. A lipopolysaccharide of chemotype RcP− was analyzed and found not to contain the third heptose unit.