Structural-functional analysis of engineered protein-nanoparticle assemblies using graphene microelectrodes.

The characterization of protein-nanoparticle assemblies in solution remains a challenge. We demonstrate a technique based on a graphene microelectrode for structural-functional analysis of model systems composed of nanoparticles enclosed in open-pore and closed-pore ferritin molecules. The method readily resolves the difference in accessibility of the enclosed nanoparticle for charge transfer and offers the prospect for quantitative analysis of pore-mediated transport, while shedding light on the spatial orientation of the protein subunits on the nanoparticle surface, faster and with higher sensitivity than conventional catalysis methods.

Thermophilic Ferritin 24mer Assembly and Nanoparticle Encapsulation Modulated by Interdimer Electrostatic Repulsion.

Protein cage self-assembly enables encapsulation and sequestration of small molecules, macromolecules, and nanomaterials for many applications in bionanotechnology. Notably, wild-type thermophilic ferritin from Archaeoglobus fulgidus (AfFtn) exists as a stable dimer of four-helix bundle proteins at a low ionic strength, and the protein forms a hollow assembly of 24 protomers at a high ionic strength (∼800 mM NaCl). This assembly process can also be initiated by highly charged gold nanoparticles (AuNPs) in solution, leading to encapsulation.