Solute diffusion in lipid bilayer membranes: an atomic level study by molecular dynamics simulation

Area of Science:

• Biophysics
• Computational Chemistry
• Membrane Science

Background:

• Understanding solute transport across lipid bilayers is crucial for pharmacology and cell biology.
• Previous studies relied on macroscopic models, lacking atomic-level detail.
• Lipid bilayers form the fundamental structure of cell membranes, controlling molecular passage.

Purpose of the Study:

• To elucidate the atomic-level mechanism of solute diffusion through phospholipid bilayers.
• To compare simulation results with experimental data for small solute diffusion.
• To investigate the influence of solutes on bilayer structure and dynamics.

Main Methods:

• Conducted nearly 4 nanoseconds of all-atom molecular dynamics simulations.
• Utilized a dimyristoylphosphatidylcholine (DMPC) bilayer model with benzene solutes.
• Analyzed solute motion, diffusion rates, and interactions with bilayer components.

Main Results:

• Simulations show benzene molecules exhibit isotropic motion and free rotation at room temperature.
• Translational diffusion rates vary within the bilayer, being faster in the center than near headgroups.
• Observed a
• hopping
• diffusion mechanism with jumps up to 8 Å in 5 ps.
• Bilayer thickness remained unaffected, but hydrocarbon chain ordering showed slight perturbations.

Conclusions:

• Solute diffusion in lipid bilayers follows a
• hopping
• mechanism, akin to gas diffusion in polymers.
• Lipid bilayers are not homogeneous hydrocarbon phases; their structure influences solute transport.
• Findings provide atomic-level insights into membrane permeability and solute interactions.