Fig. 4.

Mode of action of membrane-active host defense peptides: boundaries of the schematic phase diagram of amphipathic peptide/phospholipid aggregates are given as a function of the concentration of membrane-associated peptide and the composition of the membrane from mixtures of cylindrical (phosphatidylserine, phosphatidylcholine) and truncated inverted cone lipids (cardiolipin, phosphatidylethanolamine); modified from Bechinger (2009). Membrane association of the cationic peptides is strongly increased in the presence of anionic phospholipids such as PS or cardiolipin. In the presence of cholesterol, an abundant membrane component in mammalian cells, the bilayer will be stabilized, i.e. the phase region of stable bilayers will be enhanced. Some molecular mechanisms of bilayer perturbation are schematically shown (for details see Section 4.1).