1
|
Li P, Bera S, Kumar-Saxena S, Pecht I, Sheves M, Cahen D, Selzer Y. Electron transport through two interacting channels in Azurin-based solid-state junctions. Proc Natl Acad Sci U S A 2024; 121:e2405156121. [PMID: 39110736 PMCID: PMC11331140 DOI: 10.1073/pnas.2405156121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 07/12/2024] [Indexed: 08/21/2024] Open
Abstract
The fundamental question of "what is the transport path of electrons through proteins?" initially introduced while studying long-range electron transfer between localized redox centers in proteins in vivo is also highly relevant to the transport properties of solid-state, dry metal-protein-metal junctions. Here, we report conductance measurements of such junctions, Au-(Azurin monolayer ensemble)-Bismuth (Bi) ones, with well-defined nanopore geometry and ~103 proteins/pore. Our results can be understood as follows. (1) Transport is via two interacting conducting channels, characterized by different spatial and time scales. The slow and spatially localized channel is associated with the Cu center of Azurin and the fast delocalized one with the protein's polypeptide matrix. Transport via the slow channel is by a sequential (noncoherent) process and in the second one by direct, off-resonant tunneling. (2) The two channels are capacitively coupled. Thus, with a change in charge occupation of the weakly coupled (metal center) channel, the broad energy level manifold, responsible for off-resonance tunneling, shifts, relative to the electrodes' Fermi levels. In this process, the off-resonance (fast) channel dominates transport, and the slow (redox) channel, while contributing only negligibly directly, significantly affects transport by intramolecular gating.
Collapse
Affiliation(s)
- Ping’an Li
- Department of Chemical Physics, School of Chemistry, Tel Aviv University, Tel Aviv69978, Israel
| | - Sudipta Bera
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot76100, Israel
| | - Shailendra Kumar-Saxena
- Department of Physics and Nanotechnology, College of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur603203, Tamil Nadu, India
| | - Israel Pecht
- Department of Regenerative Biology and Immunology, Weizmann Institute of Science, Rehovot76100, Israel
| | - Mordechai Sheves
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot76100, Israel
| | - David Cahen
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot76100, Israel
| | - Yoram Selzer
- Department of Chemical Physics, School of Chemistry, Tel Aviv University, Tel Aviv69978, Israel
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
López-Ortiz M, Zamora RA, Giannotti MI, Gorostiza P. The Protein Matrix of Plastocyanin Supports Long-Distance Charge Transport with Photosystem I and the Copper Ion Regulates Its Spatial Span and Conductance. ACS NANO 2023; 17:20334-20344. [PMID: 37797170 DOI: 10.1021/acsnano.3c06390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/07/2023]
Abstract
Charge exchange is the fundamental process that sustains cellular respiration and photosynthesis by shuttling electrons in a cascade of electron transfer (ET) steps between redox cofactors. While intraprotein charge exchange is well characterized in protein complexes bearing multiple redox sites, interprotein processes are less understood due to the lack of suitable experimental approaches and the dynamic nature of the interactions. Proteins constrained between electrodes are known to support electron transport (ETp) through the protein matrix even without redox cofactors, as the charges housed by the redox sites in ET are furnished by the electrodes. However, it is unknown whether protein ETp mechanisms apply to the interprotein medium present under physiological conditions. We study interprotein charge exchange between plant photosystem I (PSI) and its soluble redox partner plastocyanin (Pc) and address the role of the Pc copper center. Using electrochemical scanning tunneling spectroscopy (ECSTS) current-distance and blinking measurements, we quantify the spatial span of charge exchange between individual Pc/PSI pairs and ETp through transient Pc/PSI complexes. Pc devoid of the redox center (Pcapo) can exchange charge with PSI at longer distances than with the copper ion (Pcholo). Conductance bursts associated with Pcapo/PSI complex formation are higher than in Pcholo/PSI. Thus, copper ions are not required for long-distance Pc/PSI ETp but regulate its spatial span and conductance. Our results suggest that the redox center that carries the charge in Pc is not necessary to exchange it in interprotein ET through the aqueous solution and question the canonical view of tight complex binding between redox protein partners.
Collapse
Affiliation(s)
- Manuel López-Ortiz
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
- CIBER-BBN, ISCIII, Barcelona 08028, Spain
| | - Ricardo A Zamora
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
- CIBER-BBN, ISCIII, Barcelona 08028, Spain
| | - Marina I Giannotti
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
- CIBER-BBN, ISCIII, Barcelona 08028, Spain
- Department of Materials Science and Physical Chemistry, University of Barcelona, Martí i Franquès 1-11, Barcelona 08028, Spain
| | - Pau Gorostiza
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, Baldiri Reixac 10-12, Barcelona 08028, Spain
- CIBER-BBN, ISCIII, Barcelona 08028, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona 08010, Spain
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Engelbrekt C, Nazmutdinov RR, Shermukhamedov S, Ulstrup J, Zinkicheva TT, Xiao X. Complex single‐molecule and molecular scale entities in electrochemical environments: Mechanisms and challenges. ELECTROCHEMICAL SCIENCE ADVANCES 2021. [DOI: 10.1002/elsa.202100157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Christian Engelbrekt
- Department of Chemistry Technical University of Denmark Building 207, DK0‐2800 Kgs. Lyngby Denmark
| | - Renat R. Nazmutdinov
- Department of Inorganic Chemistry Kazan National Research Technological University Karl Marx Str. 68 Kazan 420015 Russian Federation
| | - Shokirbek Shermukhamedov
- Department of Inorganic Chemistry Kazan National Research Technological University Karl Marx Str. 68 Kazan 420015 Russian Federation
| | - Jens Ulstrup
- Department of Chemistry Technical University of Denmark Building 207, DK0‐2800 Kgs. Lyngby Denmark
| | - Tamara T. Zinkicheva
- Department of Inorganic Chemistry Kazan National Research Technological University Karl Marx Str. 68 Kazan 420015 Russian Federation
| | - Xinxin Xiao
- Department of Chemistry Technical University of Denmark Building 207, DK0‐2800 Kgs. Lyngby Denmark
| |
Collapse
|
6
|
Abstract
The field of molecular electronics is currently experiencing a renaissance [...]
Collapse
|