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Roldán-Piñero C, Romero-Muñiz C, Díez-Pérez I, Vilhena JG, Pérez R, Cuevas JC, Zotti LA. Efficient Electron Hopping Transport through Azurin-Based Junctions. J Phys Chem Lett 2023; 14:11242-11249. [PMID: 38059566 PMCID: PMC10726356 DOI: 10.1021/acs.jpclett.3c02702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 10/27/2023] [Accepted: 11/09/2023] [Indexed: 12/08/2023]
Abstract
We conducted a theoretical study of electron transport through junctions of the blue-copper azurin from Pseudomonas aeruginosa. We found that single-site hopping can lead to either higher or lower current values compared to fully coherent transport. This depends on the structural details of the junctions as well as the alignment of the protein orbitals. Moreover, we show how the asymmetry of the IV curves can be affected by the position of the tip in the junction and that, under specific conditions, such a hopping mechanism is consistent with a fairly low temperature dependence of the current. Finally, we show that increasing the number of hopping sites leads to higher hopping currents. Our findings, from fully quantum calculations, provide deep insight to help guide the interpretation of experimental IV curves on highly complex systems.
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Affiliation(s)
- Carlos Roldán-Piñero
- Departamento
de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Carlos Romero-Muñiz
- Departamento
de Física de la Materia Condensada, Universidad de Sevilla, PO Box 1065, 41080 Sevilla, Spain
| | - Ismael Díez-Pérez
- Department
of Chemistry, Faculty of Natural & Mathematical Sciences, King’s College London, Britannia House, 7 Trinity Street, London SE1 1DB, U.K.
| | - J. G. Vilhena
- Departamento
de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
| | - Rubén Pérez
- Departamento
de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
| | - Juan Carlos Cuevas
- Departamento
de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
| | - Linda A. Zotti
- Departamento
de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
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2
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Papp E, Vattay G, Romero-Muñiz C, Zotti LA, Fereiro JA, Sheves M, Cahen D. Experimental Data Confirm Carrier-Cascade Model for Solid-State Conductance across Proteins. J Phys Chem B 2023; 127:1728-1734. [PMID: 36790863 DOI: 10.1021/acs.jpcb.2c07946] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The finding that electronic conductance across ultrathin protein films between metallic electrodes remains nearly constant from room temperature to just a few degrees Kelvin has posed a challenge. We show that a model based on a generalized Landauer formula explains the nearly constant conductance and predicts an Arrhenius-like dependence for low temperatures. A critical aspect of the model is that the relevant activation energy for conductance is either the difference between the HOMO and HOMO-1 or the LUMO+1 and LUMO energies instead of the HOMO-LUMO gap of the proteins. Analysis of experimental data confirms the Arrhenius-like law and allows us to extract the activation energies. We then calculate the energy differences with advanced DFT methods for proteins used in the experiments. Our main result is that the experimental and theoretical activation energies for these three different proteins and three differently prepared solid-state junctions match nearly perfectly, implying the mechanism's validity.
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Affiliation(s)
- Eszter Papp
- Department of Physics of Complex Systems, Eötvös Loránd University, Egyetem tér 1-3., H-1053 Budapest, Hungary
| | - Gábor Vattay
- Department of Physics of Complex Systems, Eötvös Loránd University, Egyetem tér 1-3., H-1053 Budapest, Hungary
| | - Carlos Romero-Muñiz
- Departamento de Física Aplicada I, Universidad de Sevilla, E-41012 Seville, Spain
| | - Linda A Zotti
- Departamento de Física Teórica de la Materia Condensada and IFIMAC, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Jerry A Fereiro
- School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram - 695551 Kerala, India
| | - Mordechai Sheves
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, 76100 Rehovot, Israel
| | - David Cahen
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, 76100 Rehovot, Israel
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3
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Qiu X, Chiechi RC. Printable logic circuits comprising self-assembled protein complexes. Nat Commun 2022; 13:2312. [PMID: 35484124 PMCID: PMC9050843 DOI: 10.1038/s41467-022-30038-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 04/08/2022] [Indexed: 11/09/2022] Open
Abstract
This paper describes the fabrication of digital logic circuits comprising resistors and diodes made from protein complexes and wired together using printed liquid metal electrodes. These resistors and diodes exhibit temperature-independent charge-transport over a distance of approximately 10 nm and require no encapsulation or special handling. The function of the protein complexes is determined entirely by self-assembly. When induced to self-assembly into anisotropic monolayers, the collective action of the aligned dipole moments increases the electrical conductivity of the ensemble in one direction and decreases it in the other. When induced to self-assemble into isotropic monolayers, the dipole moments are randomized and the electrical conductivity is approximately equal in both directions. We demonstrate the robustness and utility of these all-protein logic circuits by constructing pulse modulators based on AND and OR logic gates that function nearly identically to simulated circuits. These results show that digital circuits with useful functionality can be derived from readily obtainable biomolecules using simple, straightforward fabrication techniques that exploit molecular self-assembly, realizing one of the primary goals of molecular electronics. Proteins are promising molecular materials for next-generation electronic devices. Here, the authors fabricated printable digital logic circuits comprising resistors and diodes from self-assembled photosystem I complexes that enable pulse modulation.
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Affiliation(s)
- Xinkai Qiu
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands. .,Optoelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK.
| | - Ryan C Chiechi
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands. .,Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, United States.
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4
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Kontkanen OV, Biriukov D, Futera Z. Reorganization Free Energy of Copper Proteins in Solution, in Vacuum, and on Metal Surfaces. J Chem Phys 2022; 156:175101. [DOI: 10.1063/5.0085141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Metalloproteins, known to efficiently transfer electronic charge in biological systems, recently found their utilization in nanobiotechnological devices where the protein is placed into direct contact with metal surfaces. The feasibility of oxidation/reduction of the protein redox sites is affected by the reorganization free energies, one of the key parameters determining the transfer rates. While their values have been measured and computed for proteins in their native environments, i.e., in aqueous solution, the reorganization free energies of dry proteins or proteins adsorbed to metal surfaces remain unknown. Here, we investigate the redox properties of blue copper protein azurin, a prototypical redox-active metalloprotein previously probed by various experimental techniques both in solution and on metal/vacuum interfaces. We used a hybrid QM/MM computational technique based on DFT to explore protein dynamics, flexibility, and corresponding reorganization free energies in aqueous solution, vacuum, and on vacuum gold interfaces. Somewhat surprisingly, the reorganization free energy only slightly decreases when azurin is dried because the loss of the hydration shell leads to larger flexibility of the protein near its redox site. At the vacuum gold surfaces, the energetics of the structure relaxation depends on the adsorption geometry, however, significant reduction of the reorganization free energy was not observed. These findings have important consequences for the charge transport mechanism in vacuum devices, showing that the free energy barriers for protein oxidation remain significant even under ultra-high vacuum conditions.
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Affiliation(s)
| | - Denys Biriukov
- Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences, Czech Republic
| | - Zdenek Futera
- University of South Bohemia in Ceske Budejovice Faculty of Science, Czech Republic
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5
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Bím D, Alexandrova AN. Electrostatic regulation of blue copper sites. Chem Sci 2021; 12:11406-11413. [PMID: 34667549 PMCID: PMC8447924 DOI: 10.1039/d1sc02233d] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 07/26/2021] [Indexed: 01/06/2023] Open
Abstract
In the last 50 years, the blue copper proteins became central targets of investigation. Extensive experiments focused on the Cu coordination to probe the effect of local perturbations on its properties. We found that local electric fields, generated by charged residues evolutionarily placed throughout the protein edifice, mainly second sphere, but also more remotely, constitute an additional significant factor regulating blue copper proteins. These fields are not random, but exhibit a highly specific directionality, negative with respect to the and vectors in the Cu first shell. The field magnitude contributes to fine-tuning of the geometric and electronic properties of Cu sites in individual blue copper proteins. Specifically, the local electric fields evidently control the Cu–SMet bond distance, Cu(ii)–SCys bond covalency, and the energies of the frontier molecular orbitals, which, in turn, govern the Cu(ii/i) reduction potential and the relative absorption intensities at 450 nm and 600 nm. Intramolecular electric fields in blue copper proteins are oriented in a fixed way to modulate properties of their copper sites: they control the first-shell copper interactions to influence geometric, spectroscopic, and redox behavior.![]()
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Affiliation(s)
- Daniel Bím
- Department of Chemistry and Biochemistry, University of California, Los Angeles 607 Charles E. Young Drive East Los Angeles CA 90095-1569 USA
| | - Anastassia N Alexandrova
- Department of Chemistry and Biochemistry, University of California, Los Angeles 607 Charles E. Young Drive East Los Angeles CA 90095-1569 USA .,California NanoSystems Institute, University of California, Los Angeles 570 Westwood Plaza Los Angeles California 90095-1569 USA
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6
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The Role of Metal Ions in the Electron Transport through Azurin-Based Junctions. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11093732] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We studied the coherent electron transport through metal–protein–metal junctions based on a blue copper azurin, in which the copper ion was replaced by three different metal ions (Co, Ni and Zn). Our results show that neither the protein structure nor the transmission at the Fermi level change significantly upon metal replacement. The discrepancy with previous experimental observations suggests that the transport mechanism taking place in these types of junctions is probably not fully coherent.
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7
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Direct Electrochemical Enzyme Electron Transfer on Electrodes Modified by Self-Assembled Molecular Monolayers. Catalysts 2020. [DOI: 10.3390/catal10121458] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Self-assembled molecular monolayers (SAMs) have long been recognized as crucial “bridges” between redox enzymes and solid electrode surfaces, on which the enzymes undergo direct electron transfer (DET)—for example, in enzymatic biofuel cells (EBFCs) and biosensors. SAMs possess a wide range of terminal groups that enable productive enzyme adsorption and fine-tuning in favorable orientations on the electrode. The tunneling distance and SAM chain length, and the contacting terminal SAM groups, are the most significant controlling factors in DET-type bioelectrocatalysis. In particular, SAM-modified nanostructured electrode materials have recently been extensively explored to improve the catalytic activity and stability of redox proteins immobilized on electrochemical surfaces. In this report, we present an overview of recent investigations of electrochemical enzyme DET processes on SAMs with a focus on single-crystal and nanoporous gold electrodes. Specifically, we consider the preparation and characterization methods of SAMs, as well as SAM applications in promoting interfacial electrochemical electron transfer of redox proteins and enzymes. The strategic selection of SAMs to accord with the properties of the core redox protein/enzymes is also highlighted.
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8
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Fereiro JA, Bendikov T, Pecht I, Sheves M, Cahen D. Protein Binding and Orientation Matter: Bias-Induced Conductance Switching in a Mutated Azurin Junction. J Am Chem Soc 2020; 142:19217-19225. [PMID: 33141577 PMCID: PMC7662909 DOI: 10.1021/jacs.0c08836] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Indexed: 02/07/2023]
Abstract
We observe reversible, bias-induced switching of conductance via a blue copper protein azurin mutant, N42C Az, with a nearly 10-fold increase at |V| > 0.8 V than at lower bias. No such switching is found for wild-type azurin, WT Az, up to |1.2 V|, beyond which irreversible changes occur. The N42C Az mutant will, when positioned between electrodes in a solid-state Au-protein-Au junction, have an orientation opposite that of WT Az with respect to the electrodes. Current(s) via both proteins are temperature-independent, consistent with quantum mechanical tunneling as dominant transport mechanism. No noticeable difference is resolved between the two proteins in conductance and inelastic electron tunneling spectra at <|0.5 V| bias voltages. Switching behavior persists from 15 K up to room temperature. The conductance peak is consistent with the system switching in and out of resonance with the changing bias. With further input from UV photoemission measurements on Au-protein systems, these striking differences in conductance are rationalized by having the location of the Cu(II) coordination sphere in the N42C Az mutant, proximal to the (larger) substrate-electrode, to which the protein is chemically bound, while for the WT Az that coordination sphere is closest to the other Au electrode, with which only physical contact is made. Our results establish the key roles that a protein's orientation and binding nature to the electrodes play in determining the electron transport tunnel barrier.
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Affiliation(s)
- Jerry A. Fereiro
- Department
of Materials and Interfaces, Weizmann Institute
of Science, Rehovot 76100, Israel
| | - Tatyana Bendikov
- Department
of Chemical Research Support, Weizmann Institute
of Science, Rehovot 76100, Israel
| | - Israel Pecht
- Department
of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Mordechai Sheves
- Department
of Organic Chemistry, Weizmann Institute
of Science, Rehovot 76100, Israel
| | - David Cahen
- Department
of Materials and Interfaces, Weizmann Institute
of Science, Rehovot 76100, Israel
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9
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Pradhan B, Engelhard C, Van Mulken S, Miao X, Canters GW, Orrit M. Single electron transfer events and dynamical heterogeneity in the small protein azurin from Pseudomonas aeruginosa. Chem Sci 2019; 11:763-771. [PMID: 34123050 PMCID: PMC8146731 DOI: 10.1039/c9sc05405g] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 11/25/2019] [Indexed: 01/07/2023] Open
Abstract
Monitoring the fluorescence of single-dye-labeled azurin molecules, we observed the reaction of azurin with hexacyanoferrate under controlled redox potential yielding data on the timing of individual (forward and backward) electron transfer (ET) events. Change-point analysis of the time traces demonstrates significant fluctuations of ET rates and of mid-point potential E 0. These fluctuations are a signature of dynamical heterogeneity, here observed on a 14 kDa protein, the smallest to date. By correlating changes in forward and backward reaction rates we found that 6% of the observed change events could be explained by a change in midpoint potential, while for 25% a change of the donor-acceptor coupling could explain the data. The remaining 69% are driven by variations in complex association constants or structural changes that cause forward and back ET rates to vary independently. Thus, the observed spread in individual ET rates could be related in a unique way to variations in molecular parameters. The relevance for the understanding of metabolic processes is briefly discussed.
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Affiliation(s)
- Biswajit Pradhan
- Huygens-Kamerlingh Onnes Laboratory, Leiden University 2300 RA Leiden Netherlands
| | | | | | - Xueyan Miao
- School of Public Health, Guilin Medical University 541004 Guilin China
| | - Gerard W Canters
- Huygens-Kamerlingh Onnes Laboratory, Leiden University 2300 RA Leiden Netherlands
| | - Michel Orrit
- Huygens-Kamerlingh Onnes Laboratory, Leiden University 2300 RA Leiden Netherlands
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