Solid-state Protein-based Reversible Biased-induced Tunneling Current Switch.
A sample type protein monolayer, that can be a stepping stone to practical devices, can behave as an electrically-driven switch. This feat is achieved using a redox protein, Cytochrome C, with its heme shielded from direct contact with the solid-state electrodes. Ab initio DFT calculations, carried out on the whole CytC-on-Au structure, show that coupling of the heme, the origin of the protein frontier orbitals, to the electrodes is sufficiently weak to prevent Fermi level pinning. Thus, external bias can bring these orbitals in and out of resonance with the electrode. Using a CytochromeC mutant for direct protein-S-Au bonding, ~80% of the Au-CytC-Au junctions show at 0.5V bias a clear conductance peak, consistent with resonant tunneling. The ON-OFF change persists up to room temperature, demonstrating reversible, bias-controlled switching of a protein ensemble, which, with its built-in redundancy, provides a realistic path to protein-bioelectronics.