Indolicidin is a relative small 13-residue antimicrobial peptide that exhibits activity against Gram-positive and Gram-negative bacteria, as well as fungi. The basis for its antimicrobial action is believed to be membrane disruption. Indolicidin in a useful model peptide because it is non-structured, and has both hydrophobic properties due to the tryptophan residue and is charged due to its alkaline residues, resulting in interactions with a broad range of lipids.<br/>We have investigated how Indolicidin interact with lipid vesicles and the surface of lipid bilayers consisting of different lipids (with altering charge density) using different techniques including Small Angle X-ray scattering (SAXS), Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), Nano- Differential Scanning Calorimetry (DSC) and Dynamic Light Scattering (DLS).<br/>SAXS experiments has shown that Indolicidin interacts with a model cell membrane causing a change in the contrast of the bilayer. Based on analysis of the results we can see that the peptide does not seem to affect the structure of the bilayer significantly, but situates in the interface between the lipid head group and the tail in the outer leaflet in the bilayer.<br/>This is further supported by DSC where a shift and broadening of the melting lipid temperature upon addition of the peptide is observed. This indicates an associated disordering of the packing of the lipid tails in the bilayer of the vesicles. QCM-D experiments further confirms the disruption of the bilayer but also suggest removal of lipids upon flushing peptide solution over the bilayer surface.

Indolicidin as a model antimicrobial peptide: investigating their interactions with lipid vesicles and supported bilayers

255th National Meeting (2018)

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