Intercalant Aggregation Promotes Nanoscopic Depletion in Droplet Interface Bilayers

Area of Science:

• Membrane biophysics
• Lipid bilayer dynamics
• Molecular interactions

Background:

• Free volume in lipid bilayers is critical for membrane properties like fluidity and permeability.
• Hydrophobic molecules within bilayers affect free volume, and their solidification can lead to bilayer thinning.
• Understanding these interactions is key to modulating membrane functions.

Purpose of the Study:

• To investigate the inclusion and exclusion behaviors of various hydrocarbon intercalants within lipid bilayers.
• To quantify the impact of these intercalants on bilayer thickness.
• To elucidate the relationship between intercalant properties and their effect on membrane structure.

Main Methods:

• Quantification of lipid bilayer thickness.
• Analysis of hydrocarbon intercalant behavior (inclusion/exclusion).
• Investigating the effects of molecular size, chain length, and crystallizability.

Main Results:

• Long-chain squalane was expelled due to excluded volume effects.
• Smaller intercalants (n-decane, p-xylene, tetralin) were incorporated, increasing bilayer thickness.
• Crystallizable intercalants (naphthalene, durene) were excluded, causing bilayer thinning via depletion forces.

Conclusions:

• Bilayer thickness and free volume are modulated by the inclusion or exclusion of hydrophobic molecules.
• The crystallizability and size of intercalants dictate their behavior within the bilayer.
• Findings advance fundamental understanding of biological membranes and inform synthetic membrane design.