Structure-activity relationships of bacterial outer-membrane permeabilizers based on polymyxin B heptapeptides.

ABSTRACT

A series of cationic cyclic heptapeptides based on polymyxin B have been synthesized for use as permeabilizers of the outer membrane of Gram-negative bacteria. Only analogs with the Dab(2)-d-Phe(3)-Leu(4)-Xxx(5) sequence (Xxx = Dab or Orn) showed a synergistic bactericidal effect when combined with conventional antibiotics, indicating that the Dab(2) residue plays a critical role in permeation of the outer membrane of Gram-negative bacteria.