Question

How to separate them if the antimicrobial peptides and liposomes are combined？

Answer 1

By the use or application of small angle X-ray & neutron scattering (SAXS/SANS) detailed theoretical modelling we have elucidated the structure of the antimicrobial peptide, indolicidin, and the interaction with model lipid membranes of different anionic lipid compositions mimicking typical charge densities found in the cytoplasmic membrane of bacteria.

Firstly we show that indolicidin displays a predominantly disordered, random chain conformation in solution with a small fraction (≈1%) of fiber-like nanostructures that are not dissolved at higher temperatures. The peptide is shown to strongly interact with the membranes at all charge densities without significantly perturbing the lipid bilayer structure. Instead, the results show that indolicidin inserts into the outer leaflet of the lipid vesicles causing a reduced local order of the lipid packing. This result is supported by an observed change in the melting point of the lipids upon addition of the peptide, as seen by differential scanning calorimetry experiments.

The peptide does not affect the thickness of the membrane physiologically relevant concentrations & using contrast variation SANS we can show that the peptide does not affect the random lateral distribution of anionic lipids in the membrane.

These results infers that the structural aspects of the mode of action of antimicrobial peptides can be elucidated in detail using SAS techniques with liposomes as model systems