Immunochemical studies on free lipid A from Proteus mirabilis 1959.

The chemical composition and serological activity of free lipid A from Proteus were studied. Only two fatty acids: myristic acid and 3-hydroxymyristic acid were detected. When calculated for glucosamine disaccharide unit, 2 moles of ester-linked and 1 mole of amide-linked fatty acid are present. Amino group of glucosaminyl residue is substituted by 3-hydroxymyristic acid. The occurence of an uncommon (4-aminoarabinose) substituent, attached outside the backbone, was noticed. The results of serological investigation indicate the great similarity between antigenic determinants of Proteus lipid A and Salmonella-type of lipid.