A Classical Molecular Dynamics Simulation Study of Interfacial and Bulk Solution Aggregation Properties of...

Area of Science:

• Biochemistry
• Surface Chemistry
• Computational Chemistry

Background:

• Rhamnolipids are biodegradable biosurfactants produced by *Pseudomonas aeruginosa*.
• They exhibit significant surface activity, making them valuable in various applications.
• Understanding their aggregation behavior is crucial for optimizing their use.

Purpose of the Study:

• Investigate the structural and aggregation properties of nonionic dirhamnolipid.
• Compare dirhamnolipid behavior at the air-water interface and in bulk water with monorhamnolipid.
• Analyze the impact of the second rhamnose group and alkyl chain length on aggregation.

Main Methods:

• Molecular dynamics simulations were employed.
• Simulations were conducted at the air-water interface and in bulk water.
• Structural analysis and comparison with monorhamnolipid data were performed.

Main Results:

• Dirhamnolipid showed no significant change in aggregation at the air-water interface compared to monorhamnolipid.
• Increased molecular weight led to a larger surface area per monomer for dirhamnolipid.
• In bulk water, dirhamnolipid formed smaller micelles (∼N22) than monorhamnolipid (∼N40).
• Enhanced hydrophobicity in dirhamnolipid balanced the hydrophilic component, supporting micelle formation with longer alkyl chains.

Conclusions:

• The second rhamnose group in dirhamnolipid influences bulk water aggregation but not interfacial behavior.
• Hydrophobicity plays a key role in dirhamnolipid micelle formation, especially with longer alkyl chains.
• Dirhamnolipids offer tunable properties for potential applications based on their aggregation characteristics.