Anomalous Diffusion of Polyelectrolyte Segments on Supported Charged Lipid Bilayers

Area of Science:

• Polymer physics
• Surface science
• Computational biophysics

Background:

• Anomalous diffusion is crucial for understanding polymer dynamics on surfaces.
• Heterogeneous surfaces with dynamic adsorption sites present complex diffusion behaviors.
• Supported lipid bilayers offer a biologically relevant platform for studying polymer-surface interactions.

Purpose of the Study:

• To develop and apply mesoscale models for anomalous polymer diffusion on heterogeneous surfaces.
• To investigate the diffusion of polymer chains on supported lipid bilayers with varying charge densities.
• To compare simulation results with experimental observations of DNA-membrane interactions.

Main Methods:

• Mesoscale modeling using the "bead-spring" and oxDNA models.
• Brownian dynamics simulations on supported lipid bilayer membranes.
• Systematic variation of charged lipid molar fractions to tune surface heterogeneity.

Main Results:

• "Bead-spring" polymer chains demonstrated sub-diffusion on charged lipid bilayers, consistent with experimental data for short DNA segments.
• Non-Gaussian diffusion behaviors were not observed for the simulated DNA segments.
• A short double-stranded DNA (17 base pairs) simulated with the oxDNA model exhibited normal diffusion on cationic lipid bilayers.

Conclusions:

• The "bead-spring" model effectively captures sub-diffusion dynamics of polymers on charged lipid bilayers.
• Short DNA chains experience less heterogeneous energy landscapes, leading to normal diffusion, unlike longer chains.
• Simulation results highlight the influence of chain length and surface charge distribution on diffusion mechanisms.