Binding, Unbinding and Aggregation of Crescent-Shaped Nanoparticles on Tubular Lipid Membranes*

The binding of crescent-shaped nanoparticles (NPs) on nanoscale tubular lipid membranes is investigated through systematic coarse-grained molecular dynamics simulations of an implicit-solvent model. We consider NPs that adhere to the outer surface of the tubule through their concave side. The binding/unbinding transition is highly first-order, with the binding energy, E_b, being higher than that of the unbinding energy, E_u. The energy barrier between the bound and unbound states increases with increasing the NP's arclength L_np or curvature mismatch μ=R_c/R_np, where R_c and R_np are the radii of curvature of the tubule and the NP, respectively. Moreover, the binding and unbinding threshold energies increase with increasing L_np or μ. NPs lie perpendicularly to the tubule's axis for μ > 1. However, for μ smaller than a specic arclength-dependent mismatch μ*<1 , the NPs are tilted with respect to the tubule's axis, with the tilt angle that increases with decreasing μ. We also investigated theaggregation of the NPs on the tubule as a function of L_np and μ, and found that the particles self-assemble into chains for high L_np and μ>1, while for μ^*<μ<1, the NPS are distributed uniformely. The NPs also aggregate into chains for μ<μ^*.