Surfactant-Mediated Structural Modulations to Planar, Amphiphilic Multilamellar Stacks

Area of Science:

• Biochemistry and Biophysics
• Materials Science
• Self-Assembly

Background:

• The hydrophobic effect drives amphiphilic self-assembly into lamellar and micellar structures, crucial for biological processes.
• Understanding lipid-surfactant interactions is vital for biochemical technologies like membrane protein isolation and purification.

Purpose of the Study:

• To investigate the structural organization of mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and two zwitterionic surfactants (DDAPS and O-Lyso-PC).
• To explore how water vapor hydration influences the formation and properties of these mixed mesophases.

Main Methods:

• X-ray diffraction measurements to analyze structural organization.
• Microscopy techniques including brightfield optical, wide-field fluorescence, and atomic force microscopy (AFM) for morphological and topographical analysis.
• Assembly of lipid-surfactant mixtures via water vapor hydration.

Main Results:

• Multilamellar mesophases formed across a broad range of POPC:surfactant ratios, exceeding classical limits without significant disruption.
• Increased surfactant concentration generally decreased lamellar spacing (D) and headgroup-to-headgroup distance (Dhh), with variable water layer thickness (Dw).
• AFM revealed homogeneous multilamellar stacks with consistent bilayer thickness and rupture force, irrespective of surfactant concentration.

Conclusions:

• Specific chemical interactions between surfactants and POPC, including headgroup hydration and tail mismatch, dictate the structural properties of mixed mesophases.
• These findings demonstrate the formation of unique mixed mesophases with tunable structural trends, impacting dissolution pathways of lipid mesophases.
• The study highlights how surfactant-lipid interactions can modulate mesophase morphology, offering insights into biochemical separation and reconstitution processes.