Vibration assisted electron tunneling through nano-gaps in graphene nano-ribbons for amino-acid and peptide bond recognition

Aerolysin nanopore-based identification of proteinogenic amino acids using a bipolar peptide probe

Nanopore technology has attracted extensive attention due to its rapid, highly sensitive, and label-free performance. In this study, we aimed to identify proteinogenic amino acids using a wild-type aerolysin nanopore. Specifically, bipolar peptide probes were synthesised by linking four aspartic acid residues to the N-terminal and five arginine residues to the C-terminal of individual amino acids. With the help of the bipolar peptide carrier, 9 proteinogenic amino acids were reliably recognised based on current blockade and dwell time using an aerolysin nanopore. Furthermore, by changing the charge of the peptide probe, two of the five unrecognized amino acids above mentioned were identified. These findings promoted the application of aerolysin nanopores in proteinogenic amino acid recognition.

Ab Initio Properties of Hybrid Cove-Edged Graphene Nanoribbons as Metallic Electrodes for Peptide Sequencing via Transverse Tunneling Current

Recently synthesized metallic cove-edged graphene nanoribbons are considered for use as one-dimensional (1D) electrodes for ideal atomistically resolved recognition of amino acids. To this purpose a narrow nanogap device is considered, and the transversal tunneling current flowing across it is calculated during the translocation of a model Gly homopeptide using the nonequilibrium Green function scheme, based on density functional theory. We show that the signal collected from the metallic spin states is characterized by a double peak per residue in analogy with the results obtained with 1D graphene nanoribbon template electrodes. The presented results pave the way for experimentally feasible atomistically resolved tunneling current recognition using metallic edge engineered graphene electrodes obtained by bottom-up fabrication strategies.

Gap Size Dependence of Atomistic-Resolved Peptide Bond Signals by Tunneling Current Across Nano-Gaps of Graphene Nano-Ribbons

According to the recent literature, it has been demonstrated that the atomistic scale recognition of amino acids and peptide-bonds in polypeptides and proteins is in principle possible by measuring the tunneling current flowing across a narrow nano-gap in graphene nano ribbons during the peptide translocation. In this paper, we concentrate on the tunneling current signal properties measured for nano-gaps of different sizes. Using the non equilibrium Green function method based on the density functional theory, we have studied the tunneling current for larger gap sizes that can be actually realized according to the present state of the art sub-nanometer nano-pore and nano-gap technology. Also in these cases the peptide bond can be still recognized, the obtained signal being well within the measurable range of the current. The signal shapes undergo a change from a double peak feature per peptide bond for narrow gaps to a structured single peak signal per peptide bond for wider gaps. The reason is related to the different orbital overlap range of the two contributions giving rise to the original double peak signal for narrow gaps.