(698h) Simulations of the Diffusive Behavior of DNA Adsorbed on Charged Lipid Bilayers

The diffusivity and conformation of DNA adsorbed on positively charged lipid bilayers measured in experiments were found greatly deviating from theoretical predictions. The unexpected phenomena include sub-diffusion and drastic change of DNA diffusivity and conformations. Moreover, they are especially profound when the charge density of lipid bilayers is high and the ionic strength of the solution is low. To understand the observations, we used Brownian dynamics to simulate the behavior of DNA adsorbed on charged lipid bilayers. Three different scenarios were simulated: fixed lipid bilayers with a uniform charge distribution, fixed lipid bilayers with a fixed but nonuniform charge distribution and flowable lipid bilayers with lipids diffusing freely in the bilayers. From the simulation results, we found that the normal diffusion of the adsorbed DNA results from the diffusive motion of the lipids while the sub-diffusion is caused by the presence of the fixed charges in the lipid bilayers. By changing the lipid charge density and the solution ionic strength, we also found in simulations that the drastic change of DNA diffusivity and conformation observed in experiments is also due to the presence of the fixed charges in the lipid bilayers.