Speaker
Ms
Josefine Eilsø Nielsen
(University of Oslo)
Description
Antibiotic resistance is one of the biggest threats to global health, according to the world health organization. Antimicrobial peptides (AMPs) is a group of molecules that are a natural part of the human immune system, shown to have effect against a broad spectrum of pathogens including both gram positive and gram negative bacteria.1 AMPs seem to be able to evade much of the bacterial resistance mechanisms, and are therefore promising candidates for future antibiotics. Instead of blocking specific biochemical pathways as most available antibiotic agents today, AMPs act physically on the cytoplasmic membrane itself. The precise microscopic mechanism for the perturbation of the membrane is not fully clear but several theories has been suggested including membrane deformation and pore forming which could lead to changes in the lipid dynamics, lateral and transversal composition and proton/ion transfer.2
Here we have used state of the art neutron and x-ray scattering techniques to investigate the microscopic mechanism of action of antimicrobial peptides with biomembranes as models for human and bacterial cell membranes. SAXS measurements on a model peptide, Indolicidin together with DMPC-DMPG-DMPE-PEG vesicles (with increasing amount of negatively charged DMPG) has shown that Indolicidin interacts with the model cell membrane causing a change in the contrast of the bilayer. Based on analysis of the results it seems that the peptide is situated at the interface between the lipid head group and the tail in the outer leaflet in the bilayer without significantly perturbing the structure of the bilayer. 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. Preliminary SANS results do not indicate change in the lateral distribution of lipids which has been suggested as a possible mechanism on3).
When combining the results from scattering methods, together with other complimentary techniques, we gain profound biophysical understanding of these systems. This knowledge can be used in the development of new antibiotics for the future based on antimicrobial peptides designed specifically for the task.
1. Fjell, C. D.; Hiss, J. A.; Hancock, R. E. W.; Schneider, G., Nat. Rev. Drug Discov. 2011, 11 (1), 37-51.
2. Nguyen, L. T.; Haney, E. F.; Vogel, H. J., Trends in biotechnology 2011, 29 (9), 464-472.
3. Epand, R. M.; Epand, R. F., Biochimica et Biophysica Acta (BBA)-Biomembranes 2009, 1788 (1), 289-294.
Primary author
Ms
Josefine Eilsø Nielsen
(University of Oslo)
Co-authors
Prof.
Håvard Jenssen
(Roskilde University)
Prof.
Marité Cárdenas
(Malmö University)
Prof.
Reidar Lund
(Department of Chemistry, University of Oslo)
Dr
Tania Kjellerup Lind
(Malmö University)
Ms
Victoria Ariel Bjørnestad
(University of Oslo)
