Structural and conductivity properties of lipid-coated melittin peptide nanowires molded at air-water interface

[Display omitted] •Lipid phase acts as an inductor of melittin nanowires in lipid/peptide mixtures.•Melittin nanowires coated by lipids form amyloid-like structures.•Coated melittin nanowires showed a distinctive lateral conductivity. The studies of the interaction of bioactive natural short peptide molecules with lipids are increasing in different fields including bio-electronics. In biological context, for the melittin peptide, it is important to understand its mechanism of action on cell membranes since its lytic activity was linked to its pharmaceutical action in some antiviral lipidic formulations for external use. By using Langmuir monolayers, we show the molding effect and the conformational assembly of DSPC lipids to coat melittin peptide (termed as coated nanowires) into the lipid domains. This peculiar lipid/peptide assembly was studied by using three florescent probes: laurdan, DiC18 and thioflavin-T using confocal microscopy. We have also employed atomic force microscopy to identify the isolated core of the coated nanowires transferred into mica support after extracting them from the lipid domains due to a pull-out effect generated by water. We have also developed an ad-hoc Langmuir trough to measure monolayer lateral conductivity. With this approach, we found a distinctive lateral conductivity property of these nanowires at the air-water interface. We propose that this particular lipid:peptide arrangement could self-trigger on biological membranes promoted by the lipid physical state and, in turn, it could be a transient step of the disrupting mechanism of melittin peptide at the membrane. This may explain the properties of this peptide such as cellular toxicity and antimicrobial properties. In addition, we claim the potential possibility of the coated nanowires to develop bio-sensor nano-electronic devices such as water-gate bio-organic transistors, highlighting the role of the environmental conditions imposed by the interfacial water covered by defined lipids.