Computer simulation of short-range repulsion between supported phospholipid membranes.

Area of Science:

• Biophysics
• Computational Chemistry
• Materials Science

Background:

• Understanding intermembrane forces is crucial for biological systems and biomaterials.
• Phospholipid bilayers, like 1,2-dilauroyl-DL-phosphatidylethanolamine (DLPE), are fundamental components of cell membranes.
• Accurate modeling of water-lipid interactions is essential for simulating membrane behavior.

Purpose of the Study:

• To calculate water-mediated pressure between supported DLPE membranes using Monte Carlo simulations.
• To analyze the contributions of hydration, electrostatic, dispersion, and steric forces to intermembrane pressure.
• To assess the impact of force field parameters on simulated hydration and pressure.

Main Methods:

• Grand canonical Monte Carlo simulations were employed.
• A united-atom AMBER-based force field for DLPE and a TIP4P model for water were used.
• Interactions were analyzed by partitioning total pressure into hydration and direct interaction components.

Main Results:

• The chosen force field exaggerates membrane water affinity, leading to overestimated hydration and intermembrane pressure.
• Hydration and pressure are highly sensitive to the strength of water-lipid interactions.
• Damping water-lipid interactions by 10%-20% significantly altered the relative contributions of individual pressure components.

Conclusions:

• Current force fields may overestimate water-lipid interactions in DLPE membrane simulations.
• Precise parameterization of water-lipid interactions is critical for accurate predictions of intermembrane forces.
• Further refinement of force fields is needed for reliable biomembrane simulations.