Interaction of polymyxin B and A deacilated derivative with monolayers of bacterial lipids

Polymyxin B (PxB) is a polycationic peptide antibiotic produced by gram-positive bacteria Bacillus polymyxia, and is highly selective against gram-negative organisms. In the present work we have studied the interaction of PxB and PxB-nonapeptide (NF'), with lipid monolayers of a lipidic extract from Escherichia coli, a bacteria susceptible to PxB. Kinetics of insertion of both peptides at different surface pressures are compared. Also, the effect of peptides on the phase behaviour of the monolayers is determined from the compression isotherms.