Lipid A, the lipid component of bacterial lipopolysaccharides: relation of chemical structure to biological activity.

TLDR: The conclusion is reached that the highly ordered and compact lipid A structure confers stability to the outer membrane, renders it less permeable to lipophilic molecules and by providing a proper fluidity stabilizes the conformation of biologically active membrane proteins.

Abstract: Lipopolysaccharides are integral components of the outer membrane of Gram-negative bacteria and they participate in various membrane functions essential for bacterial growth and survival. Lipopolysaccharides also represent the endotoxins of Gram-negative bacteria and possibly play a role for the pathogenesis and manifestations of bacterial infections. These biological activities are mediated mainly by the lipid component of lipopolysaccharides, termed lipid A. Chemically, lipid A consists of a β1,6-linkedD-glucosamine disaccharide which carries substituted phosphoryl groups and a range ofD-3-hydroxy andD-3-acyloxyacyl residues, the latter being arranged in a hexagonal dense packing.