The cationic polypeptide polymyxin B, has been demonstrated to form a stable molecular
complex with the lipid A region of bacterial lipopolysaccharides. The interaction between
polymyxin B and LPS appears to be stoichiometric, with several lines of evidence
suggesting that one molecule of polymyxin B binds one monomer unit of LPS. The formation
of LPS-polymyxin B complexes results in the generation of higher mol. wt aggregates with
decreased isopynic density.