Lipopolysaccharides, abbreviated as LPS, are large glycolipid molecules. They consist of three structural domains: Lipid A, the core oligosaccharide and the O-antigen. Lipid A is the hydrophobic portion of the molecule; it is an acetylated β-1'-6-linked glucosamine disaccharide that forms the outer leaflet of the outer membrane. Mature Lipid A is predominantly hexacylated. The core oligosaccharide is a non-repeating oligosaccharide segment linked to the glucosamine in Lipid A. Its core structure typically comprises 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo), a heptosaccharide and various hexosaccharides; these sugars may be modified by phosphate groups and other substituents (such as phosphoethanolamine). The O-antigen is an extended polysaccharide segment attached to the core oligosaccharide, consisting of repeating oligosaccharide chains comprising two to eight sugars [1].
