Related Experiment Video
Updated: Jun 21, 2026
Modeling Ligands into Maps Derived from Electron Cryomicroscopy
Published on: July 19, 2024
Characterization of antibiotic peptide pores using cryo-EM and comparison to neutron scattering
Mikyung Han1, Yuan Mei, Htet Khant
1Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.
Abstract:
Magainin, a 23-residue antibiotic peptide, interacts directly with the lipid bilayer leading to cell lysis in a strongly concentration-dependent fashion. Utilizing cryo-electron microscopy, we have directly observed magainin interacting with synthetic DMPC/DMPG membranes. Visual examination shows that visibly unperturbed vesicles are often found adjacent to vesicles that are lysed or porous, demonstrating that magainin disruption is a highly stochastic process. Quantitatively, power spectra of large numbers of porous vesicles can be averaged together to produce the equivalent of an electron scattering curve, which can be related to theory, simulation, and published neutron scattering experiments. We demonstrate that magainin-induced pores in lipid vesicles have a mean diameter of approximately 80 A, compatible with earlier reported results in multilayer stacks. In addition to establishing a connection between experiments in multilayer stacks and vesicles, this also demonstrates that computed power spectra from windowed-out regions of cryo-EM images can be compared to neutron scattering data in a meaningful way, even though the pores of interest cannot yet be individually identified in images. Cryo-EM offers direct imaging of systems in configurations closely related to in vivo conditions, whereas neutron scattering has a greater variety of mechanisms for specific contrast variation via D2O and deuterated lipids. Combined, the two mechanisms support each other, and provide a clearer picture of such 'soft' systems than either could provide alone.
Insights
Magainin antibiotic peptides disrupt lipid membranes stochastically. Cryo-electron microscopy revealed magainin-induced pores in vesicles, averaging 80 angstroms, aiding understanding of membrane interactions.
Area of Science:
- Biophysics
- Membrane Biology
- Microscopy
Background:
- Magainin is a 23-residue antibiotic peptide known to interact with lipid bilayers.
- This interaction leads to cell lysis in a concentration-dependent manner.
- The precise mechanism of magainin-induced membrane disruption remains under investigation.
Purpose of the Study:
- To directly visualize and quantify magainin's interaction with synthetic lipid membranes using cryo-electron microscopy (cryo-EM).
- To characterize the size and nature of magainin-induced pores in lipid vesicles.
- To correlate cryo-EM findings with neutron scattering data and theoretical models.
Main Methods:
- Utilized cryo-electron microscopy (cryo-EM) to observe magainin interacting with dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DMPC/DMPG) membranes.
- Analyzed power spectra from cryo-EM images of porous vesicles to generate scattering curves.
- Compared computed power spectra with published neutron scattering data and theoretical models.
Main Results:
- Direct visualization confirmed magainin's interaction with lipid bilayers, showing both unperturbed and lysed vesicles, indicating a stochastic disruption process.
- Averaged power spectra from porous vesicles yielded scattering curves comparable to theoretical and neutron scattering data.
- Magainin-induced pores in lipid vesicles were quantified with a mean diameter of approximately 80 angstroms.
Conclusions:
- Cryo-electron microscopy provides direct imaging of magainin-membrane interactions under near-physiological conditions.
- The study establishes a quantitative link between vesicle and multilayer stack experiments.
- Combining cryo-EM with neutron scattering offers a comprehensive approach to studying soft matter systems like lipid membranes.
