Surface Coating Structure and Its Interaction with Cytochrome c in EG₆-Coated Nanoparticles Varies with Surface Curvature

The composition, orientation, and conformation of proteins in biomolecular coronas acquired by nanoparticles in biological media contribute to how they are identified by a cell. While numerous studies have investigated protein composition in biomolecular coronas, relatively little detail is known about how the nanoparticle surface influences the orientation and conformation of the proteins associated with them. We previously showed that the peripheral membrane protein cytochrome c adopts preferred poses relative to negatively charged 3-mercaptopropionic acid (MPA)-gold nanoparticles (AuNPs). Here, we employ molecular dynamics simulations and complementary experiments to establish that cytochrome c also assumes preferred poses upon association with nanoparticles functionalized with an uncharged ligand, specifically ω-(1-mercaptounde-11-cyl)hexa(ethylene glycol) (EG₆). We find that the display of the EG₆ ligands is sensitive to the curvature of the surface - and, consequently, the effective diameter of the nearly spherical nanoparticle core - which in turn affects the preferred poses of cytochrome c.