Lipid-dependent pore formation by antimicrobial peptides arenicin-2 and melittin demonstrated by their proton transfer activity.

This work presents a comparative study of proton transfer activity (PTA) of two cationic (+6) antimicrobial peptides, β-structural arenicin-2 and α-helical melittin. A new approach was proposed for the detection of passive proton transfer by using proteoliposomes containing bacteriorhodopsin, which creates a small light-induced electrochemical proton gradient ∆ΔpH. Addition of several nanomoles of the peptides lowers ∆ΔpH that is proximately indicative of the pore formation.

Conformation of gramicidin A in Triton X-100 micelles from CD and FTIR data: a clean example of antiparallel double β5.6 helix formation.

The linear peptide gramicidin A (gA) forms prototypical ion channels specific for monovalent cations and has been extensively used to study the organization and dynamics of membrane channels. This polymorphic peptide can adopt two different types of structures, the helical dimer β6.3 ('channel state') and the double helical structure with two intertwined monomers.

Molecular mechanism of action of β-hairpin antimicrobial peptide arenicin: oligomeric structure in dodecylphosphocholine micelles and pore formation in planar lipid bilayers.

The membrane-active, cationic, β-hairpin peptide, arenicin, isolated from marine polychaeta Arenicola marina exhibits a broad spectrum of antimicrobial activity. The peptide in aqueous solution adopts the significantly twisted β-hairpin conformation without pronounced amphipathicity. To assess the mechanism of arenicin action, the spatial structure and backbone dynamics of the peptide in membrane-mimicking media and its pore-forming activity in planar lipid bilayers were studied.

[ESR study of the interaction of cytotoxin II with model membranes].

Cytotoxin II from the venom of the Central-Asian cobra Naja oxiana spin-labeled at Lys35 (SLCT II) was studied by ESR spectroscopy in aqueous solution and upon interaction with phospholipid vesicles from egg phosphatidylcholine or its mixture with dimyristoylphosphatidylglycerol (molar ratio 9:1). The distribution of SLCT II between the aqueous and lipid phases depended on the toxin and lipid concentrations and on the solution ionic strength. It was analyzed using the modified Gouy-Chapman equation that takes into account different charges of the cytotoxin in solution and in membrane.