Real-time monitoring of melittin-induced pore and tubule formation from supported lipid bilayers and its physiological relevance

The temporal evolution of effects of antimicrobial peptide melittin on supported phospholipid bilayers (SPBs) containing negatively charged phospholipids was monitored by ellipsometry and laser scanning microscopy together with measurements of lipid mobility by Z-scan fluorescence correlation spectroscopy. Under all conditions used in our study, we observed reproducibly two effects. The first one is formation of pores in the SPB, which occupy approximately 40% of the bilayer. The formation of pores was accompanied by a decrease in lateral diffusion coefficient of the lipids to approximately 60% of its initial value. The second, simultaneous, effect is the formation of tubules of approximately 30 nm radius and length of the order of 10 μm. Flushing of the sample with excess of buffer removes most of the tubules, but it does not affect the pores. Further experiments performed under various conditions demonstrated reproducibility of both phenomena.