[Comparative effect of polymyxin B on lipid bilayer membranes with different lipid composition]

The aim of the work was to characterize the role of negatively charged lipids (cardiolipin and lauric acid) in the increase of ionic permeability of the membrane under the action of polymyxin B. Cardiolipin or lauric acid were added into membrane-forming solution in concentration close to that in the membrane of bacterial cell. It resulted in modification of membranes by these lipids. The obtained membranes had a higher ionic permeability in the presence of polymyxin B. However the comparison of different effects can lead to the conclusion that free fatty acid are responsible for the major part of the effect. It is concluded that the character of damage of the bilayer by polymyxin is diverse: polymyxin B forms ionic canals with lauric acid, whereas there is unspecific destruction of BLM by the polymyxin interacting with cardiolipin.