Abstract
The transversal tunneling current flowing across a narrow nanogap is employed for amino acid 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 nonequilibrium 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 of the polarity of AAs considered. Both X (Asn, Ala, Asp, Ser) homopeptides and Gly–X heteropeptides have been considered, showing that the major role is played by the electrons injected through the CαH group and the partially resonant peptide bonds. Because of 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 heteropeptides, 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.
Highlights
IntroductionEngineering strategies to improve the signal are required.[14] A different strategy, already proposed for sensing biomolecules,[15] employs the measurement of the transversal tunneling current flowing between two nanoelectrodes during the protein translocation across a nanogap
To support the rising importance of proteomics, efficient and cheap protein sequencing techniques are required to address the huge protein population in the human body, 2 orders of magnitude larger than the human genome
We have studied the DFT−NEGF method for the elastic tunneling current flowing across a nanogap in narrow graphene nanoribbons (GNRs) during the translocation of some model peptides made of neutral polar (Asp, Asn) and apolar (Ala) amino acid (AA)
Summary
Engineering strategies to improve the signal are required.[14] A different strategy, already proposed for sensing biomolecules,[15] employs the measurement of the transversal tunneling current flowing between two nanoelectrodes during the protein translocation across a nanogap In this case the AA recognition can be attained by measuring the transversal tunneling current that should reflect the chemical and physical nature of the piece of molecule occupying the nanogap at a given time.[11,16,17] Both these schemes require controlled translocation dynamics of the protein (in its primary structure state) that is still an open technological issue, but the second one allows, in principle, the measurements of AA-related signals with atomistic resolution using the instrumental bandwidth currently available (see Section 2)
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