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Updated: Aug 14, 2026
Synthesis of Compound Giant Unilamellar Vesicles: A Biomimetic Model of Nucleate Cells
Published on: July 3, 2025
Single giant unilamellar vesicle method reveals effect of antimicrobial peptide magainin 2 on membrane permeability
Yukihiro Tamba1, Masahito Yamazaki
1Materials Science, Graduate School of Science and Engineering, Shizuoka University, Shizuoka 422-8529, Japan.
Abstract:
It is thought that magainin 2, an antimicrobial peptide, acts by binding to lipid membranes. Recent studies using a suspension of large unilamellar vesicles (LUVs) indicate that magainin 2 causes gradual leakage from LUVs containing negatively charged lipids. However, the details of the characteristics of the membrane permeability and the mechanism of pore formation remain unclear. In this report, we investigated the interaction of magainin 2 with single giant unilamellar vesicles (GUVs) composed of a dioleoylphosphatidylcholine and dioleoylphosphatidylglycerol mixture (50% DOPG/50% DOPC GUVs) containing the fluorescent dye, calcein, by phase contrast, fluorescence microscopy using the single GUV method. Low concentrations (3-10 microM) of magainin 2 caused the rapid leakage of calcein from single GUVs but did not disrupt the liposomes or change the membrane structure, showing directly that magainin 2 forms membrane pores through which calcein leaked. The rapid leakage of calcein from a GUV started stochastically, and once it began, the complete leakage occurred rapidly (6-60 s). The fraction of completely leaked GUV, P(L), increased with time and also with an increase in magainin 2 concentration. Shape changes in these GUVs occurred prior to the pore formation and also at lower concentrations of magainin 2, which could not induce the pore formation. Their analysis indicates that binding of magainin 2 to the external monolayer of the GUV increases its membrane area, thereby raising its surface pressure. The addition of lysophosphatidylcholine into the external monolayer of GUVs increased P(L). On the basis of these results, we propose the two-state transition model for the pore formation.
Insights
Magainin 2, an antimicrobial peptide, rapidly forms pores in lipid membranes, causing calcein leakage from giant unilamellar vesicles. This pore formation is linked to membrane area changes and surface pressure, suggesting a two-state transition model.
Area of Science:
- Biophysics
- Membrane Biology
- Antimicrobial Peptides
Background:
- Antimicrobial peptides like magainin 2 are thought to interact with lipid membranes.
- Previous studies with large unilamellar vesicles (LUVs) suggested gradual leakage from negatively charged lipids.
- The precise mechanism of magainin 2-induced membrane permeability and pore formation remained unclear.
Purpose of the Study:
- To investigate the interaction of magainin 2 with single giant unilamellar vesicles (GUVs).
- To elucidate the characteristics of membrane permeability and the mechanism of pore formation induced by magainin 2.
- To propose a model for magainin 2-induced pore formation.
Main Methods:
- Utilized single giant unilamellar vesicles (GUVs) composed of a 50% dioleoylphosphatidylglycerol/50% dioleoylphosphatidylcholine mixture containing the fluorescent dye calcein.
- Employed phase contrast and fluorescence microscopy to observe magainin 2 interactions with GUVs.
- Analyzed GUV leakage, membrane structure, and shape changes in response to varying magainin 2 concentrations.
Main Results:
- Low concentrations (3-10 microM) of magainin 2 induced rapid calcein leakage from single GUVs without disrupting membrane structure.
- Pore formation led to complete calcein leakage within 6-60 seconds, with the fraction of leaked GUVs increasing with time and magainin 2 concentration.
- GUV shape changes preceded pore formation, suggesting magainin 2 binding increases membrane area and surface pressure.
Conclusions:
- Magainin 2 directly forms membrane pores, leading to rapid leakage of encapsulated molecules.
- GUV shape changes and increased surface pressure are critical factors preceding magainin 2-induced pore formation.
- A two-state transition model is proposed to explain the mechanism of magainin 2 pore formation in lipid bilayers.
