A self-consistent chain model for the phase transitions in lipid bilayer membranes

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Lipid bilayer membranes are crucial for cellular function.
• Understanding their mechanical and thermodynamic properties is essential for various biological and technological applications.
• Existing models often lack detailed molecular conformational descriptions.

Purpose of the Study:

• To develop a comprehensive mechanical model for lipid bilayer membranes.
• To describe the internal conformations of lipid molecules using an isomeric bond-rotation scheme.
• To represent thermodynamic properties using a density matrix incorporating intermolecular interactions.

Main Methods:

• Utilized an isomeric bond-rotation scheme to model lipid molecule conformations.
• Employed a density matrix to represent thermodynamic properties.
• Incorporated Kihara potential for interchain interactions and considered Coulomb interactions and lateral pressure.
• Calculations performed for DMPC, DPPC, and DSPC lipid molecules.

Main Results:

• The model accurately predicted the gel-to-liquid crystalline phase transition temperature and latent heat.
• Successfully reproduced temperature dependencies of intermolecular distance, gauche bonds, order parameter, membrane volume, thermal expansion coefficients, and birefringence.
• Demonstrated good agreement with experimental data for DMPC, DPPC, and DSPC.

Conclusions:

• The developed mechanical model provides a robust framework for understanding lipid bilayer membrane behavior.
• The model's ability to match diverse experimental data validates its predictive power.
• This approach offers insights into molecular-level contributions to macroscopic membrane properties.