An atomic force microscopy study of the interactions between indolicidin and supported planar bilayers

Area of Science:

• Biophysics
• Membrane Biophysics
• Antimicrobial Peptides

Background:

• Indolicidin is a tryptophan-rich antimicrobial peptide.
• Understanding peptide-membrane interactions is crucial for antimicrobial drug development.

Purpose of the Study:

• To investigate the real-time interaction of indolicidin with model lipid membranes.
• To elucidate the mechanism of indolicidin's antimicrobial action at the membrane level.

Main Methods:

• In situ atomic force microscopy (AFM) on supported planar bilayers.
• Dye leakage experiments using phosphatidylcholine vesicles.

Main Results:

• Indolicidin induced shrinking and thinning of lipid bilayers.
• Effects were dependent on membrane composition and physical properties.
• Indolicidin fluidised membranes, leading to dye release (calcein leakage).
• Interaction was most pronounced at gel-fluid domain boundaries.

Conclusions:

• Indolicidin's mode of action involves a stepwise interaction with lipid membranes.
• Membrane fluidisation and dye release occur, but pore formation is not supported by the data.