Freezing of stressed bilayers and vesicles

Area of Science:

• Biophysics
• Materials Science
• Computational Chemistry

Background:

• Lipid bilayers exhibit complex phase behaviors crucial for cellular function.
• Understanding phase transition decoupling and anomalous freezing in vesicles is key to membrane biophysics.

Purpose of the Study:

• To develop a theoretical framework explaining phase transition decoupling in lipid bilayers.
• To investigate the causes of anomalous freezing in lipid vesicles.
• To predict and validate novel physical phenomena in lipid systems.

Main Methods:

• Development of a minimalistic theoretical framework.
• Application of the framework to lipid vesicles.
• Coarse-grained molecular dynamics simulations.

Main Results:

• Phase transition decoupling in lipid bilayers is caused by nonuniform stress from asymmetric lipid distribution.
• Anomalous freezing in vesicles arises from stress asymmetry due to lipid tail extension upon freezing.
• A previously unknown dependence of surface tension on temperature was predicted and observed.

Conclusions:

• Stress asymmetry is a unifying mechanism for phase transition decoupling and anomalous vesicle freezing.
• The findings suggest potential relevance for thermosensitive protein gating mechanisms.