Au Nanoparticles in Lipid Bilayers: A Comparison between Atomistic and Coarse-Grained Models

The computational study of the interaction between charged, ligand-protected metal nanoparticles and model lipid membranes has been recently addressed at both atomistic and coarse-grained levels. Here we compare the performance of three versions of the coarse-grained Martini force field at describing the nanoparticle-membrane interaction. The three coarse-grained models differ in terms of treatment of long-range electrostatic interactions and water polarizability. The NP-membrane interaction consists of the transition from a metastable NP-membrane complex, in which the NP is only partially embedded in the membrane, to a configuration in which the NP is anchored to both membrane leaflets. All three of the coarse-grained models provide a description of the metastable NP-membrane complex that is consistent with that obtained using an atomistic force field. As for the anchoring transition, the polarizable-water Martini correctly describes the molecular mechanisms and the energetics of the transition. The standard version of the Martini model, instead, underestimates the free-energy barriers for anchoring and does not completely capture the membrane deformations involved in the transition process.