Composition of lipid A in the S and R forms of Shigella dysenteriae serovar 1

A chemical analysis was performed of lipid A, isolated by acid hydrolysis of the lipopolysaccharide from the S and R forms of Shigella dysenteriae serovar 1. Differences in the moiety of both lipids and sugars were compared. The lipid portion consisted of a homologous series of fatty acids ranging from C12:0 to C18:0 (predominant homologues, C12:0, C14:0 and C16:0) and the homologous series of 3-hydroxy acids ranging from C12:0 to C16:0 (predominant homologue, 3-OH-C14:0). The major sugar portion consisted of D-glucosamine. The toxicity of lipid A in mice (LD50) ranged between 300-400 micrograms/mouse, and values from the Limulus amebocyte lysate assay were recorded as titres of 10(-5) to 10(-6) mg/ml.