A Solid‐State Protein Junction Serves as a Bias‐Induced Current Switch

Fereiro, Jerry A.; Kayser, Ben; Romero‐Muñiz, Carlos; Vilan, Ayelet; Долгих, Д. А.; Chertkova, Rita V.; Cuevas, Juan Carlos; Zotti, Linda A.; Pecht, Israel; Sheves, Mordechai

doi:10.1002/ange.201906032

Cited by 8 publications

(9 citation statements)

References 32 publications

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“…Intriguingly, the conduction mechanism changes qualitatively in the resonant regime where the protein valence-band edge is aligned with the Fermi energy as reported recently for cytochrome c ( 47 ) and earlier for azurin. 48 In this scenario, the electron transport is dominated by the familiar Fe d(t 2g )-heme orbitals that mediate electron hopping in solution, more specifically by linear combinations thereof with contributions of 2–3 hemes that bridge the space between the electrodes.…”

supporting

confidence: 74%

Coherent Electron Transport across a 3 nm Bioelectronic Junction Made of Multi-Heme Proteins

Futera

Ide

Kayser

et al. 2020

J. Phys. Chem. Lett.

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Multi-heme cytochromes (MHCs) are fascinating proteins used by bacterial organisms to shuttle electrons within, between, and out of their cells. When placed in solid-state electronic junctions, MHCs support temperature-independent currents over several nanometers that are 3 orders of magnitude higher compared to other redox proteins of similar size. To gain molecular-level insight into their astonishingly high conductivities, we combine experimental photoemission spectroscopy with DFT+Σ current–voltage calculations on a representative Gold-MHC-Gold junction. We find that conduction across the dry, 3 nm long protein occurs via off-resonant coherent tunneling, mediated by a large number of protein valence-band orbitals that are strongly delocalized over heme and protein residues. This picture is profoundly different from the electron hopping mechanism induced electrochemically or photochemically under aqueous conditions. Our results imply that the current output in solid-state junctions can be even further increased in resonance, for example, by applying a gate voltage, thus allowing a quantum jump for next-generation bionanoelectronic devices.

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supporting

confidence: 74%

Coherent Electron Transport across a 3 nm Bioelectronic Junction Made of Multi-Heme Proteins

Futera

Ide

Kayser

et al. 2020

J. Phys. Chem. Lett.

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“…Intriguingly, the conduction mechanism changes qualitatively in the resonant regime where the protein valence-band edge is aligned with the Fermi energy as reported recently for cytochrome c [56] and earlier for azurin [57]. In this scenario, the electron transport is dominated by the familiar Fe d(t 2g )-heme orbitals that mediate electron hopping in solution, more specifically by linear combinations thereof with contributions on 2-3 hemes that bridge the space between the electrodes.…”

Section: Discussionsupporting

confidence: 54%

Off-resonant coherent electron transport over three nanometers in multi-heme protein bioelectronic junctions

Futera,

Ide,

Kayser

et al. 2020

Preprint

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Multi-heme cytochromes (MHC) are fascinating proteins used by bacterial organisms to shuttle electrons within and between their cells. When placed in a solid state electronic junction, they support temperature-independent currents over several nanometers that are three orders of magnitude higher compared to other redox proteins of comparable size. To gain microscopic insight into their astonishingly high conductivities, we present herein the first current-voltage calculations of its kind, for a MHC sandwiched between two Au(111) electrodes, complemented by photo-emission spectroscopy experiments. We find that conduction proceeds via off-resonant coherent tunneling mediated by a large number of protein valence-band orbitals that are strongly delocalized over heme and protein residues, effectively "gating" the current between the two electrodes. This picture is profoundly different from the dominant electron hopping mechanism supported by the same protein in aqueous solution. Our results imply that current output in MHC junctions could be even further increased in the resonant regime, e.g. by application of a gate voltage, making these proteins extremely interesting for nextgeneration bionanoelectronic devices.Author contributions: Z.F. carried out the computer simulations, B.K., K.G. and I.P. performed the experimental I-V measurements, I.I. and H.I. performed the experimental UPS measurements, X.J. modelled the I-V curves,

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“…While this is also confirmed by naïve DFT calculations of porphyrins in the gas phase (SI Appendix, Computational Details), which show that the frontier molecular orbitals (FMOs) do not reside on the metal center of the porphyrin, we cannot rely on these calculations in our study, as the use of the BSA mat does not permit us to know the exact protein structure, the exact binding configuration of the porphyrins to the BSA, and, accordingly, the formation of any axial ligands to the metal center. The latter axial ligands, such as to histidine residues or water molecules, are crucial for the location of the molecular orbitals (39,44). Instead, the mentioned DFT calculations of Blumberger and coworkers (43), based on a known crystal structure of the protein, do show a molecular-orbitals delocalization of the valence band across several heme molecules and argue that this valence-band delocalization is responsible to efficient ETp involving a coherent transport mechanism.…”

Section: Discussionmentioning

confidence: 98%

The porphyrin ring rather than the metal ion dictates long-range electron transport across proteins suggesting coherence-assisted mechanism

Agam

Nandi

Kaushansky

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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The fundamental biological process of electron transfer (ET) takes place across proteins with common ET pathways of several nanometers. Recent discoveries push this limit and show long-range extracellular ET over several micrometers. Here, we aim in deciphering how protein-bound intramolecular cofactors can facilitate such long-range ET. In contrast to natural systems, our protein-based platform enables us to modulate important factors associated with ET in a facile manner, such as the type of the cofactor and its quantity within the protein. We choose here the biologically relevant protoporphyrin molecule as the electron mediator. Unlike natural systems having only Fe-containing protoporphyrins, i.e., heme, as electron mediators, we use here porphyrins with different metal centers, or lacking a metal center. We show that the metal redox center has no role in ET and that ET is mediated solely by the conjugated backbone of the molecule. We further discuss several ET mechanisms, accounting to our observations with possible contribution of coherent processes. Our findings contribute to our understanding of the participation of heme molecules in long-range biological ET.

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A Solid‐State Protein Junction Serves as a Bias‐Induced Current Switch

Cited by 8 publications

References 32 publications

Coherent Electron Transport across a 3 nm Bioelectronic Junction Made of Multi-Heme Proteins

Coherent Electron Transport across a 3 nm Bioelectronic Junction Made of Multi-Heme Proteins

Off-resonant coherent electron transport over three nanometers in multi-heme protein bioelectronic junctions

The porphyrin ring rather than the metal ion dictates long-range electron transport across proteins suggesting coherence-assisted mechanism

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