Chemical structure of the core region of Escherichia coli J-5 lipopolysaccharide.

The lipopolysaccharide of Escherichia coli J-5 was sequentially de-O-acylated, dephosphorylated, reduced, de-N-acylated, and N-acetylated. The products were separated by high-performance anion-exchange chromatography into a nonasaccharide (1), two octasaccharides (2, 3), and a heptasaccharide (4). Compositional analysis, methylation analysis, and NMR spectroscopy revealed the structures of the products as: alpha-D-GlcpNAc-(1-7)-L-alpha-D-Hepp-(1-7)-[alpha-D-Glcp-(1-3)-]-L -alpha-D- Hepp-(1-3)-R1, (1) L-alpha-D-Hepp-(1-7)-[alpha-D-Glcp-(1-3)-]-L-alpha-D-Hepp-(1 -3)-R1, (2) alpha-D-GlcpNAc-(1-7)-L-alpha-D-Hepp-(1-7)-[alpha-D-Glcp-(1-3)-]-L -alpha-D- Hepp-(1-3)-R2, (3) alpha-D-Glcp-(1-3)-L-alpha-D-Hepp-(1-3)-R1, (4) in which 1R is L-alpha-D-Hepp-(1-5)-[alpha-Kdop-(2-4)-]-alpha-Kdop-(2 -6)- beta-D-GlcpNAc-(1-6)-D-GlcN-Acol, and 2R is L-alpha-D-Hepp-(1-5)-alpha-Kdop-(2-6)-beta-D-GlcpNAc-(1-6 )-D- GlcNAcol (LD-Hep, L-glycero-D-manno-heptose; Kdo, 3-deoxy-D-manno-octulopyranosonic acid; GlcNAcol, 2-acetamido-2-deoxy-glucitol). Fast-atom-bombardment mass spectrometry of de-O-acylated and dephosphorylated lipopolysaccharide showed that the isolated oligosaccharides represented the complete carbohydrate moiety of the lipopolysaccharide, and indicated that the non-reducing terminal D-GlcN residue in lipopolysaccharide was present as the free base.