Polymyxin B and Ca2+ induce conductivity fluctuations in bilayer lipid membranes from dipalmitoylphosphatidic acid

Polymyxin B in micromolar concentrations induces current fluctuations in li quid crystalline bilayer lipid membranes from dipalmitoylphosphatidic acid identified as ion channels. The appearance of ion channels correlates with phase separation of the lipid in the presence of peptide polycations detect ed by differential scanning calorimetry. Ca2+ also induces the formation of ion channels in liquid crystalline bilayer lipid membranes from dipalmitoy lphosphatidic acid followed by the phase transition of the phospholipid. Th e capacitive current, which indicates the possibility of structural transfo rmations of bilayer - non-bilayer type (hexagonal phase II), precedes the f ormation of Ca2+-induced channels in bilayer lipid membranes from dipalmito ylphosphatidic acid.