Electronic Conductance Resonance in Non-Redox-Active Proteins

Abstract

Bioelectronics research has mainly focused on redox-active proteins because of their role in biological charge transport. In these proteins, electronic conductance is a maximum when electrons are injected at the known redox potential of the protein. It has been shown recently that many non-redox-active proteins are good electronic conductors, though the mechanism of conduction is not yet understood. Here, we report single-molecule measurements of the conductance of three non-redox-active proteins, maintained under potential control in solution, as a function of electron injection energy. All three proteins show a conductance resonance at a potential ∼0.7 V removed from the nearest oxidation potential of their constituent amino acids. If this shift reflects a reduction of reorganization energy in the interior of the protein, it would account for the long-range conductance observed when carriers are injected into the interior of a protein.

Electric field stimulates production of highly conductive microbial OmcZ nanowires

“…In contrast, biological systems can construct nanomaterials at low-cost and high yield from the bottom-up 2 . Non-redox proteins are shown to be conductive in single-molecule measurements, with small electron decay with distance, provided charge is injected into the protein interior via good contact 3 . However, the conduction mechanism is unknown.…”

Distance and Potential Dependence of Charge Transport Through the P700 Reaction Center of Photosystem I

“…27,[39][40][41][42][43] These results confirm that protein conductance is larger than that of the surrounding electrolytic medium, both in metalloproteins [44][45][46] and interestingly in non-redox active proteins. 16,17 In addition, we observe that the apparent height of PSI complexes by ECSTM depends on the probe potential UP (Figure 3a). This effect allows using ECSTM imaging at different electrochemical potentials to study their conductance and charge transport properties.…”

“…61 Regarding protein-electrode interfaces, it has been proposed that charge exchange is modulated by electronic coupling between electrode Fermi level and the molecular orbitals of interfacing residues. 16,18,19,44,45,62,63 Remarkably, introducing Trp residues in 6-Alanine peptides increases their molecular conductance, lowering the effective barrier height and enhancing electronic coupling with gold electrodes. 64 In addition, cyclic voltammetry features of Az are abolished if the Trp residue mediating ETp with the electrode is mutated.…”

“…This charge exchange mechanism through a biased electrode, known as electron transport (ETp) can be achieved in ECSTM (break junction and blinking modes), conductive atomic force microscopy (C-AFM), liquid metal contacts, microfabricated gold nano wire set-ups 15 . A growing amount of evidence 14,[16][17][18] shows that ETp is a ubiquitous charge conduction mechanism through the protein matrix, and that it confers conductivities to redox and non-redox proteins outperforming molecular wires beyond 5 nm distances 19 . Although the physiological relevance of ETp through protein junctions is less studied than that of ET, understanding protein ETp is key to engineer protein-based electronic devices 14,20 .…”

Bioelectrochemistry and the Singularity Point “I Robot”?**

“…Another field of ET in proteins is the conducting proteins/peptides field. The first question that comes to mind is, can proteins be conducting or electron transferring? [26] since proteins are considered insulators. Are there any natural systems that have evolved to transfer electrons in long‐range processes?…”