Interactions of surfactin with membrane models

Area of Science:

• Biochemistry
• Biophysics
• Materials Science

Background:

• Surfactin is a potent biosurfactant produced by Bacillus subtilis.
• It exhibits various biological activities and has a cyclic lipopeptide structure.
• Understanding its interaction with lipid membranes is crucial for its applications.

Purpose of the Study:

• To investigate the interaction of ionized surfactin with lipid vesicles and monolayers.
• To elucidate the role of calcium ions in surfactin-lipid interactions.
• To determine the miscibility and penetration behavior of surfactin in phospholipid membranes.

Main Methods:

• Circular dichroism (CD) spectroscopy to monitor surfactin-lecithin vesicle interactions.
• Surface pressure measurements of mixed surfactin/phospholipid monolayers.
• Compression isotherms to analyze penetration and miscibility.

Main Results:

• Surfactin penetration into lipid monolayers is influenced by phospholipid charge and acyl chain length.
• Electrostatic repulsion significantly reduces surfactin penetration in DMPA monolayers.
• Calcium ions enhance surfactin penetration, especially with acidic and long-chain zwitterionic phospholipids.
• Surfactin demonstrates complete miscibility with phospholipids in mixed monolayers.
• Surfactin insertion into lipid membranes is driven by hydrophobic interactions and induces conformational changes.

Conclusions:

• Surfactin spontaneously penetrates lipid membranes through hydrophobic interactions.
• The penetration process is modulated by electrostatic forces and calcium ions.
• Surfactin's interaction with membranes is dependent on lipid composition and physicochemical conditions.
• The findings provide insights into surfactin's membrane-disrupting mechanisms and potential applications.