Triggering Amino Acid Detection by Atomistic Resolved Tunneling Current Signals in Graphene Nanoribbon Devices for Peptide Sequencing

The transversal tunneling current flowing across a narrow nanogap is employed for amino acids recognition in polypeptides during their translocation across the nanogap. An ideal device, consisting of a nanogap in graphene nanoribbons, is considered for this purpose to exploit the ideal atomistic resolution of 2D electrodes. Using the non equilibrium Green function scheme, based on the density functional theory, we have studied the trigger signal that can be collected from the backbone of some template peptides showing that this signal is practically independent on the polarity of the AAs considered. Both X (Asn, Ala, Asp) homo peptides and Gly-X etero peptides have been considered showing that the major role is played by the electrons injected through the CαH group and the partially resonant peptide bonds. Due to the smaller overall transversal size in relation to the graphene nanoribbon width, the X side chain is only partially involved in the electron injection for Gly-X etero peptides, but no role is played by the polar ends. These results encourage the search of unique triggering signals related to the passage of each residue during translocation by atomic resolved tunneling currents.