Density functional theory study of mesophase formation in model lipid systems

Area of Science:

• Soft Matter Physics
• Computational Chemistry
• Materials Science

Background:

• Phospholipids exhibit mesophases crucial for applications like drug delivery.
• Understanding phospholipid phase behavior is key for designing advanced materials.
• Coarse-grained models offer efficient simulations of complex phospholipid systems.

Purpose of the Study:

• Investigate structural properties and phase behavior of coarse-grained phospholipid models.
• Apply Percus-Yevick (PY) integral equation theory and density functional theory (DFT) to phospholipid systems.
• Elucidate the role of density, temperature, and dipolar head group strength in mesophase formation.

Main Methods:

• Utilized a coarse-grained phospholipid model with a dipolar Gay-Berne potential.
• Employed Percus-Yevick integral equation theory to calculate pair correlation functions.
• Applied classical density functional theory (DFT) to determine liquid crystalline phase transitions.
• Validated theoretical predictions against molecular dynamics simulations.

Main Results:

• Enhanced dipolar interactions stabilize ordered phases (nematic, smectic A) at low densities and high temperatures.
• Observed increased orientational and translational order parameters with stronger dipolar interactions.
• Detected heightened compressibility in the smectic phase.
• Generated phase diagrams illustrating the influence of head group strength.

Conclusions:

• Dipolar interactions significantly influence phospholipid mesophase stability.
• PY theory and DFT provide valuable insights into phospholipid phase behavior.
• Theoretical predictions show qualitative agreement with molecular dynamics simulations, despite density underestimation.