(16d) Reorientation of Cytochrome c on Silica Nanoparticles Induced By pH

An ability to control the orientation of proteins on nanoparticles has a direct impact on the properties of functional materials including purification of antibodies and modulating enzymatic activity. Thus, designing next generation of biocompatible nanomaterials requires a better understanding of the interfacial bio-nano interactions. We investigate the interaction between a model protein, cytochrome c, and silica nanoparticles over a wide range of pH by combining small-angle neutron scattering, adsorption measurements, and molecular dynamics simulations. We show that at pH < 4 the protein adsorbs with a head-on configuration, but with increasing pH, a reorientation of the protein to a side-on orientation takes place. Here, we will discuss the role of interfacial electrostatic interactions on governing the local orientation of cytochrome c on silica nanoparticles.