Abstract
Protein-based electronics is an emerging field which has attracted considerable attention over the past decade. Here, we present a theoretical study of the formation and electronic structure of a metal-protein-metal junction based on the blue-copper azurin from pseudomonas aeruginosa. We focus on the case in which the protein is adsorbed on a gold surface and is contacted, at the opposite side, to an STM (Scanning Tunneling Microscopy) tip by spontaneous attachment. This has been simulated through a combination of molecular dynamics and density functional theory. We find that the attachment to the tip induces structural changes in the protein which, however, do not affect the overall electronic properties of the protein. Indeed, only changes in certain residues are observed, whereas the electronic structure of the Cu-centered complex remains unaltered, as does the total density of states of the whole protein.
Highlights
In the emerging field of biomolecular electronics, proteins represent one of the most promising candidates to be incorporated as active elements in solid-state devices
In order to obtain an atomistic understanding of the dynamics of single-protein junctions in the blinking modality [14], we performed molecular dynamics (MD) simulations of a tip-azurin-surface junction as detailed in the methods section
Despite being anchored through its β-barrel laying flat over the surface, the azurin exhibits a pronounced mobility promoted by the soft/flexible random coil connecting the β-barrel to the α-helix giving rise to up/down motion of the latter
Summary
In the emerging field of biomolecular electronics, proteins represent one of the most promising candidates to be incorporated as active elements in solid-state devices. Their capability of catalyzing a large number of reactions together with their intrinsic possibilities in terms of chemical recognition and selectivity make them ideal to be employed as sensors [1]. An example is given by azurins, which are a class of redox metalloproteins involved in the denitrification processes, whose function is related to electron shuttling between cytochrome enzymes [5] For this reason, their electronic properties have been studied in depth [6,7,8,9,10,11,12,13]. Both sequential tunneling and fully-coherent tunneling have been proposed as plausible transport scenarios in the case of Biomolecules 2019, 9, 506; doi:10.3390/biom9090506 www.mdpi.com/journal/biomolecules
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