Plasmon resonance based analysis of a single protein conjugated Au nanoshell

The authors perform a numerical calculation of a gold nanoshell, having either a silica core or a hollow one, interacting with incident electromagnetic radiation and aggregated with a single protein on its surface, by using the discrete dipole approximation. The protein model accounts for a tertiary structure that may contain internal cavities, while the entire structure is placed either in vacuum or a uniform host medium. The authors further analyze the near field pattern by a spherical harmonic transform. Our results identify the interactions that account for the observed extinction peak and wavelength shift in related optical experiments. The theoretical basis provided in this work may be used not only to identify a single protein conjugated nanoparticle, but also to determine the cavity content of the protein by its refractive index properties, determined from optical measurements.