Related Experiment Video
Updated: Aug 15, 2026
Automated Lipid Bilayer Membrane Formation Using a Polydimethylsiloxane Thin Film
Published on: July 10, 2016
Membrane thinning due to antimicrobial peptide binding: an atomic force microscopy study of MSI-78 in lipid bilayers
Almut Mecke1, Dong-Kuk Lee, Ayyalusamy Ramamoorthy
1University of Michigan, Ann Arbor, Michigan, USA.
Abstract:
The interaction of an antimicrobial peptide, MSI-78, with phospholipid bilayers has been investigated using atomic force microscopy, circular dichroism, and nuclear magnetic resonance (NMR). Binding of amphipathic peptide helices with their helical axis parallel to the membrane surface leads to membrane thinning. Atomic force microscopy of supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers in the presence of MSI-78 provides images of the membrane thinning process at a high spatial resolution. This data reveals that the membrane thickness is not reduced uniformly over the entire bilayer area. Instead, peptide binding leads to the formation of distinct domains where the bilayer thickness is reduced by 1.1 +/- 0.2 nm. The data is interpreted using a previously published geometric model for the structure of the peptide-lipid domains. In this model, the peptides reside at the hydrophilic-hydrophobic boundary in the lipid headgroup region, which leads to an increased distance between lipid headgroups. This picture is consistent with concentration-dependent 31P and 2H NMR spectra of MSI-78 in mechanically aligned DMPC bilayers. Furthermore, 2H NMR experiments on DMPC-d54 multilamellar vesicles indicate that the acyl chains of DMPC are highly disordered in the presence of the peptide as is to be expected for the proposed structure of the peptide-lipid assembly.
Insights
Antimicrobial peptide MSI-78 causes distinct thinning domains in phospholipid bilayers, altering membrane structure. This interaction, visualized by atomic force microscopy and confirmed by NMR, reveals peptide localization within lipid headgroups.
Area of Science:
- Biophysics
- Membrane Biology
- Antimicrobial Peptides
Background:
- Antimicrobial peptides (AMPs) are crucial for innate immunity.
- Understanding their interaction with cell membranes is key to developing new therapies.
- MSI-78 is an amphipathic antimicrobial peptide.
Purpose of the Study:
- To investigate the structural consequences of MSI-78 binding to phospholipid bilayers.
- To elucidate the mechanism of membrane thinning induced by MSI-78.
- To correlate biophysical observations with a geometric model of peptide-lipid interactions.
Main Methods:
- Atomic Force Microscopy (AFM) for high-resolution imaging of supported bilayers.
- Circular Dichroism (CD) spectroscopy to assess peptide secondary structure.
- Nuclear Magnetic Resonance (NMR) spectroscopy (31P and 2H) to probe lipid and peptide dynamics and organization.
Main Results:
- AFM revealed non-uniform membrane thinning, forming distinct domains with reduced thickness (1.1 +/- 0.2 nm).
- NMR data confirmed peptide localization at the lipid headgroup interface, increasing headgroup spacing.
- 2H NMR indicated increased disorder in lipid acyl chains upon MSI-78 binding.
Conclusions:
- MSI-78 induces localized membrane thinning by forming specific peptide-lipid domains.
- The peptide's amphipathic helical structure drives its insertion at the membrane's hydrophilic-hydrophobic boundary.
- These findings support a model of peptide-induced membrane restructuring relevant to antimicrobial activity.
More Related Videos
08:58Atomic Force Microscopy Cantilever-Based Nanoindentation: Mechanical Property Measurements at the Nanoscale in Air and Fluid
Published on: December 2, 2022
10:02Neutron Spin Echo Spectroscopy as a Unique Probe for Lipid Membrane Dynamics and Membrane-Protein Interactions
Published on: May 27, 2021
