Frustrated phase transformations in supported, interdigitating lipid bilayers.

Area of Science:

• Lipid bilayer thermodynamics and phase transitions
• Surface confinement effects on lipid organization

Background:

• Monofluorinated phospholipids (F-DPPC) undergo a fluid to gel phase transition in free bilayers.
• This transition involves acyl tail ordering, increased molecular area, and decreased bilayer thickness.
• Confinement near a solid surface introduces constraints on lipid reorganization.

Purpose of the Study:

• To investigate the effects of surface confinement on the F-DPPC phase transition.
• To understand how planar topography and constant surface area influence lipid reorganization.
• To characterize the resulting phase behavior and coexistence.

Main Methods:

• Utilizing lipid bilayer models with controlled surface confinement.
• Observing phase transitions under topographical and area constraints.
• Analyzing lipid organization and phase coexistence using biophysical techniques.

Main Results:

• Surface confinement limits the formation of the energetically favored interdigitated gel phase.
• Non-interdigitated lipids experience increased lateral tension due to area constraints.
• This leads to elevated transition temperatures, supercooling, and vitrification.
• An unusual phase coexistence of two distinct gel phases is observed.

Conclusions:

• Frustrated phase transitions in confined lipid bilayers couple dynamics and thermodynamics.
• Surface constraints alter lipid phase behavior, leading to novel states.
• Understanding these confined systems is crucial for biomembrane and material science applications.