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Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P197
The interaction of antimicrobial peptides with model membranes investigated
by small angle X-ray scattering
Sebastian Linser 1 , Sergio S. Funari 2 , Regine Willumeit 1
1 GKSS Research Center, Max-Planck-Str. 1, 21502 Geesthacht, Germany –
2 Hasylab@DESY, Notkestr. 85, 22603 Hamburg, Germany
The uprising resistance of pathogenic bacteria is a severe problem in health care. To
develop new antibiotic treatment, naturally occurring antimicrobial peptides and synthetic
derivates might become potent agents. These peptides have a direct physical
impact on the membranes of their target cells and display selectivity for bacteria and
fungi in contrast to mammalian cells. In our work we tested the antibacterial activity
of the synthetic peptide NK-CS and derivatives thereof against E. coli (Gram negative)
and S. carnosus (Gram positive) bacteria as well as the hemolytic properties against
human erythrocytes to determine the selectivity of the peptides. In parallel we investigated
the interaction of the peptides with different model membranes, mimicking
bacterial and human membranes, by small angle X-ray scattering (SAXS). The combination
of these techniques gives an indication of the structure-function relationship
of this peptide-lipid-system.
Among the tested peptide, NK-CS was found to be the most potent antimicrobial peptide,
while all derivatives showed less antibacterial selectivity and activity. Structural
characterization of the interaction between the peptides and different model membranes
revealed that the peptides showed no influence on phosphatidylcholine lipids,
representing the membrane of erythrocytes, but for all tested peptides the inverse
hexagonal phase transition of phosphatidylethanolamine lipids, standing for the main
component of the bacterial membrane of E. coli, was significantly altered in a specific
manner which can be correlated with the activity of the peptides. This phase transition
temperature was increased by the peptides promoting a positive curvature of the
membranes eventually leading to the disruption of the model membranes.