Nonintercalating nanosubstrates create asymmetry between bilayer leaflets

Area of Science:

• Biophysics
• Materials Science
• Computational Chemistry

Background:

• Lipid bilayer properties are sensitive to environmental factors.
• Understanding membrane-substrate interactions is crucial for cell biology and drug delivery.

Purpose of the Study:

• To investigate the effects of nanoscopic substrates on lipid bilayer physical properties.
• To explore the role of surface hydroxyl density in substrate-bilayer interactions.
• To characterize the asymmetry induced in lipid bilayers by finite nanoscopic supports.

Main Methods:

• Molecular dynamics simulations of palmitoyl-oleoyl phosphatidylcholine bilayers.
• Exposure to model nanosized substrates with varying surface hydroxyl densities.
• Analysis of lipid bilayer properties including fluctuations, charge density, diffusion, and order parameters.

Main Results:

• A surface hydroxyl density of 10% was sufficient to juxtapose bilayers to substrates.
• Substrates induced asymmetry between bilayer leaflets in transverse lipid fluctuations, charge density profiles, and lipid diffusion rates.
• Lipid cross-sectional areas, component volumes, and order parameters were minimally affected.

Conclusions:

• Nanoscopic substrate interactions create significant leaflet asymmetry, exceeding that seen with infinite supports.
• The proximity to finite nanoscopic supports leads to stronger support-bilayer electrostatic coupling.
• Membrane interactions with nanoscopic contact points are complex and not a simple interpolation, with implications for biological systems like cytoskeleton-membrane interactions.