1
|
Bera S, Fereiro JA, Saxena SK, Chryssikos D, Majhi K, Bendikov T, Sepunaru L, Ehre D, Tornow M, Pecht I, Vilan A, Sheves M, Cahen D. Near-Temperature-Independent Electron Transport Well beyond Expected Quantum Tunneling Range via Bacteriorhodopsin Multilayers. J Am Chem Soc 2023; 145. [PMID: 37933117 PMCID: PMC10655127 DOI: 10.1021/jacs.3c09120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/19/2023] [Accepted: 10/20/2023] [Indexed: 11/08/2023]
Abstract
A key conundrum of biomolecular electronics is efficient electron transport (ETp) through solid-state junctions up to 10 nm, often without temperature activation. Such behavior challenges known charge transport mechanisms, especially via nonconjugated molecules such as proteins. Single-step, coherent quantum-mechanical tunneling proposed for ETp across small protein, 2-3 nm wide junctions, but it is problematic for larger proteins. Here we exploit the ability of bacteriorhodopsin (bR), a well-studied, 4-5 nm long membrane protein, to assemble into well-defined single and multiple bilayers, from ∼9 to 60 nm thick, to investigate ETp limits as a function of junction width. To ensure sufficient signal/noise, we use large area (∼10-3 cm2) Au-protein-Si junctions. Photoemission spectra indicate a wide energy separation between electrode Fermi and the nearest protein-energy levels, as expected for a polymer of mostly saturated components. Junction currents decreased exponentially with increasing junction width, with uniquely low length-decay constants (0.05-0.5 nm-1). Remarkably, even for the widest junctions, currents are nearly temperature-independent, completely so below 160 K. While, among other things, the lack of temperature-dependence excludes, hopping as a plausible mechanism, coherent quantum-mechanical tunneling over 60 nm is physically implausible. The results may be understood if ETp is limited by injection into one of the contacts, followed by more efficient charge propagation across the protein. Still, the electrostatics of the protein films further limit the number of charge carriers injected into the protein film. How electron transport across dozens of nanometers of protein layers is more efficient than injection defines a riddle, requiring further study.
Collapse
Affiliation(s)
- Sudipta Bera
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Jerry A. Fereiro
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
- School
of Chemistry, Indian Institute of Science
Education and Research, Thiruvananthapuram 695551, Kerala, India
| | - Shailendra K. Saxena
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
- Department
of Physics and Nanotechnology, College of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur, Chennai 603203, Tamil
Nadu, India
| | - Domenikos Chryssikos
- Molecular
Electronics, Technical University of Munich, 85748 Garching, Germany
- Fraunhofer
Institute for Electronic Microsystems and Solid State Technologies
(EMFT), 80686 München, Germany
| | - Koushik Majhi
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Tatyana Bendikov
- Department
of Chemical Research Support, Weizmann Institute
of Science, Rehovot 7610001, Israel
| | - Lior Sepunaru
- Department
of Chemistry and Biochemistry, University
of California, Santa
Barbara, California 93106, United States
| | - David Ehre
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Marc Tornow
- Molecular
Electronics, Technical University of Munich, 85748 Garching, Germany
- Fraunhofer
Institute for Electronic Microsystems and Solid State Technologies
(EMFT), 80686 München, Germany
| | - Israel Pecht
- Department
of Immunology and Regenerative Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ayelet Vilan
- Department
of Chemical and Biological Physics Weizmann
Institute of Science, Rehovot 7610001, Israel
| | - Mordechai Sheves
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - David Cahen
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| |
Collapse
|
2
|
Barrett JA, Li Z, Garcia JV, Wein E, Zheng D, Hunt C, Ngo L, Sepunaru L, Iretskii AV, Ford PC. Correction: 'Redox-mediated carbon monoxide release from a manganese carbonyl-implications for physiological CO delivery by CO releasing moieties' (2021), by Barrett et al.. R Soc Open Sci 2023; 10:231206. [PMID: 37700905 PMCID: PMC10493849 DOI: 10.1098/rsos.231206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 08/16/2023] [Indexed: 09/14/2023]
Abstract
[This corrects the article DOI: 10.1098/rsos.211022.][This corrects the article DOI: 10.1098/rsos.211022.].
Collapse
|
3
|
Roehrich B, Leung KK, Gerson J, Kippin TE, Plaxco KW, Sepunaru L. Calibration-Free, Seconds-Resolved In Vivo Molecular Measurements using Fourier-Transform Impedance Spectroscopy Interrogation of Electrochemical Aptamer Sensors. ACS Sens 2023; 8:3051-3059. [PMID: 37584531 PMCID: PMC10463274 DOI: 10.1021/acssensors.3c00632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Accepted: 08/02/2023] [Indexed: 08/17/2023]
Abstract
Electrochemical aptamer-based (EAB) sensors are capable of measuring the concentrations of specific molecules in vivo, in real time, and with a few-second time resolution. For their signal transduction mechanism, these sensors utilize a binding-induced conformational change in their target-recognizing, redox-reporter-modified aptamer to alter the rate of electron transfer between the reporter and the supporting electrode. While a variety of voltammetric techniques have been used to monitor this change in kinetics, they suffer from various drawbacks, including time resolution limited to several seconds and sensor-to-sensor variation that requires calibration to remove. Here, however, we show that the use of fast Fourier transform electrochemical impedance spectroscopy (FFT-EIS) to interrogate EAB sensors leads to improved (here better than 2 s) time resolution and calibration-free operation, even when such sensors are deployed in vivo. To showcase these benefits, we demonstrate the approach's ability to perform real-time molecular measurements in the veins of living rats.
Collapse
Affiliation(s)
- Brian Roehrich
- Department
of Chemistry and Biochemistry, University
of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Kaylyn K. Leung
- Department
of Chemistry and Biochemistry, University
of California Santa Barbara, Santa Barbara, California 93106, United States
- Center
for Bioengineering, University of California
Santa Barbara, Santa Barbara, California 93106, United States
| | - Julian Gerson
- Department
of Psychological and Brain Sciences, University
of California, Santa Barbara, California 93106, United States
- Center
for Bioengineering, University of California
Santa Barbara, Santa Barbara, California 93106, United States
| | - Tod E. Kippin
- Department
of Psychological and Brain Sciences, University
of California, Santa Barbara, California 93106, United States
- Department
of Molecular Cellular and Developmental Biology, University of California, Santa
Barbara, California 93106,United States
| | - Kevin W. Plaxco
- Department
of Chemistry and Biochemistry, University
of California Santa Barbara, Santa Barbara, California 93106, United States
- Center
for Bioengineering, University of California
Santa Barbara, Santa Barbara, California 93106, United States
| | - Lior Sepunaru
- Department
of Chemistry and Biochemistry, University
of California Santa Barbara, Santa Barbara, California 93106, United States
| |
Collapse
|
4
|
Chung J, Plaxco KW, Sepunaru L. Precise Electrochemical Sizing of Individual Electro-Inactive Particles. J Vis Exp 2023. [PMID: 37590554 DOI: 10.3791/65116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/19/2023] Open
Abstract
Nanoimpact electrochemistry enables the time-resolved in situ characterization (e.g., size, catalytic activity) of single nanomaterial units, providing a means of elucidating heterogeneities that would be masked in ensemble studies. To implement this technique with redox inactive particles, a solution-phase redox reaction is used to produce a steady-state background current on a disk ultramicroelectrode. When a particle adsorbs onto the electrode, it produces a stepwise reduction in the exposed electrode area, which produces, in turn, a stepwise decrease in the current commensurate with the size of the adsorbing species. Historically, however, nanoimpact electrochemistry has suffered from "edge effects," in which the radial diffusion layer formed at the circumference of the ultramicroelectrodes renders the step size dependent not only on the size of the particle but also on where it lands on the electrode. The introduction of electrocatalytic current generation, however, mitigates the heterogeneity caused by edge effects, thus improving the measurement precision. In this approach, termed "electrocatalytic interruption," a substrate that regenerates the redox probe at the diffusion layer is introduced. This shifts the rate-limiting step of the current generation from diffusion to the homogeneous reaction rate constant, thus reducing flux heterogeneity and increasing the precision of particle sizing by an order of magnitude. The protocol described here explains the set-up and data collection employed in nanoimpact experiments implementing this effect for improved precision in the sizing of redox in-active materials.
Collapse
Affiliation(s)
- Julia Chung
- Interdepartmental Program in Biomedical Science and Engineering, University of California at Santa Barbara
| | - Kevin W Plaxco
- Interdepartmental Program in Biomedical Science and Engineering, University of California at Santa Barbara; Department of Chemistry and Biochemistry, University of California at Santa Barbara
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California at Santa Barbara;
| |
Collapse
|
5
|
Lin YC, Masquelier E, Al Sabeh Y, Sepunaru L, Gordon MJ, Morse DE. Voltage-calibrated, finely tunable protein assembly. J R Soc Interface 2023; 20:20230183. [PMID: 37403486 DOI: 10.1098/rsif.2023.0183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/06/2023] Open
Abstract
Neuronally triggered phosphorylation drives the calibrated and cyclable assembly of the reflectin signal transducing proteins, resulting in their fine tuning of colours reflected from specialized skin cells in squid for camouflage and communication. In close parallel to this physiological behaviour, we demonstrate for the first time that electrochemical reduction of reflectin A1, used as a surrogate for charge neutralization by phosphorylation, triggers voltage-calibrated, proportional and cyclable control of the size of the protein's assembly. Electrochemically triggered condensation, folding and assembly were simultaneously analysed using in situ dynamic light scattering, circular dichroism and UV absorbance spectroscopies. The correlation of assembly size with applied potential is probably linked to reflectin's mechanism of dynamic arrest, which is controlled by the extent of neuronally triggered charge neutralization and the corresponding fine tuning of colour in the biological system. This work opens a new perspective on electrically controlling and simultaneously observing reflectin assembly and, more broadly, provides access to manipulate, observe and electrokinetically control the formation of intermediates and conformational dynamics of macromolecular systems.
Collapse
Affiliation(s)
- Yin-Chen Lin
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, CA 93106, USA
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - Eloise Masquelier
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, CA 93106, USA
- Materials Department, University of California, Santa Barbara, CA 93106, USA
| | - Yahya Al Sabeh
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, CA 93106, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106, USA
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Michael J Gordon
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, CA 93106, USA
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - Daniel E Morse
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, CA 93106, USA
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106, USA
| |
Collapse
|
6
|
Masquelier E, Taxon E, Liang SP, Al Sabeh Y, Sepunaru L, Gordon MJ, Morse DE. A new electrochemical method that mimics phosphorylation of the core tau peptide K18 enables kinetic and structural analysis of intermediates and assembly. J Biol Chem 2023; 299:103011. [PMID: 36781124 PMCID: PMC10024187 DOI: 10.1016/j.jbc.2023.103011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 02/04/2023] [Accepted: 02/08/2023] [Indexed: 02/13/2023] Open
Abstract
Tau protein's reversible assembly and binding of microtubules in brain neurons are regulated by charge-neutralizing phosphorylation, while its hyperphosphorylation drives the irreversible formation of cytotoxic filaments associated with neurodegenerative diseases. However, the structural changes that facilitate these diverse functions are unclear. Here, we analyzed K18, a core peptide of tau, using newly developed spectroelectrochemical instrumentation that enables electroreduction as a surrogate for charge neutralization by phosphorylation, with simultaneous, real-time quantitative analyses of the resulting conformational transitions and assembly. We observed a tipping point between behaviors that paralleled the transition between tau's physiologically required, reversible folding and assembly and the irreversibility of assemblies. The resulting rapidly electroassembled structures represent the first fibrillar tangles of K18 that have been formed in vitro at room temperature without using heparin or other charge-complementary anionic partners. These methods make it possible to (i) trigger and analyze in real time the early stages of conformational transitions and assembly without the need for preformed seeds, heterogenous coacervation, or crowding; (ii) kinetically resolve and potentially isolate never-before-seen early intermediates in these processes; and (iii) develop assays for additional factors and mechanisms that can direct the trajectory of assembly from physiologically benign and reversible to potentially pathological and irreversible structures. We anticipate wide applicability of these methods to other amyloidogenic systems and beyond.
Collapse
Affiliation(s)
- Eloise Masquelier
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, California, USA; Materials Department, University of California, Santa Barbara, California, USA
| | - Esther Taxon
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, California, USA; Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California, USA
| | - Sheng-Ping Liang
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, California, USA; Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
| | - Yahya Al Sabeh
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, California, USA; Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California, USA
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA
| | - Michael J Gordon
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, California, USA; Department of Chemical Engineering, University of California, Santa Barbara, California, USA
| | - Daniel E Morse
- Institute for Collaborative Biotechnologies, University of California, Santa Barbara, California, USA; Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California, USA.
| |
Collapse
|
7
|
Shlosberg Y, Brekhman V, Lotan T, Sepunaru L. Direct Electricity Production from Nematostella and Arthemia's Eggs in a Bio-Electrochemical Cell. Int J Mol Sci 2022; 23:15001. [PMID: 36499326 PMCID: PMC9738779 DOI: 10.3390/ijms232315001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 11/28/2022] [Indexed: 12/05/2022] Open
Abstract
In recent years, extensive efforts have been made to develop clean energy technologies to replace fossil fuels to assist the struggle against climate change. One approach is to exploit the ability of bacteria and photosynthetic organisms to conduct external electron transport for electricity production in bio-electrochemical cells. In this work, we first show that the sea anemones Nematostella vectensis and eggs of Artemia (brine shrimp) secrete redox-active molecules that can reduce the electron acceptor Cytochrome C. We applied 2D fluorescence spectroscopy and identified NADH or NADPH as secreted species. Finally, we broaden the scope of living organisms that can be integrated with a bio-electrochemical cell to the sea anemones group, showing for the first time that Nematostella and eggs of Artemia can produce electrical current when integrated into a bio-electrochemical cell.
Collapse
Affiliation(s)
- Yaniv Shlosberg
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
| | - Vera Brekhman
- Marine Biology Department, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa 3498838, Israel
| | - Tamar Lotan
- Marine Biology Department, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa 3498838, Israel
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
| |
Collapse
|
8
|
Quek G, Roehrich B, Su Y, Sepunaru L, Bazan GC. Conjugated Polyelectrolytes: Underexplored Materials for Pseudocapacitive Energy Storage. Adv Mater 2022; 34:e2104206. [PMID: 34626021 DOI: 10.1002/adma.202104206] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 08/21/2021] [Indexed: 06/13/2023]
Abstract
Conjugated polyelectrolytes (CPEs) are characterized by an electronically delocalized backbone bearing ionic functionalities. These features lead to properties relevant for use in energy-storing pseudocapacitor devices, including ionic conductivity, water processability, gel-formation, and formation of polaronic species stabilized by electrostatic interactions. In this Perspective, the basis for evaluating the figures of merit for pseudocapacitors is provided, together with the techniques used for their evaluation. The general utility and challenges encountered with neutral conjugated polymers are then discussed. Finally, recent advances on the use of CPEs in pseudocapacitor devices are reviewed. The article is concluded by discussing how their miscibility in aqueous media permits the incorporation of CPEs in living materials that are capable of switching function from extraction of energy from bacterial metabolic pathways to pseudocapacitor energy storage.
Collapse
Affiliation(s)
- Glenn Quek
- Departments of Chemistry and Chemical & Biomolecular Engineering, National University of Singapore, Singapore, 119077, Singapore
| | - Brian Roehrich
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Building 232, Santa Barbara, CA, 93106, USA
| | - Yude Su
- Suzhou Institute for Advanced Research, University of Science and Technology of China Suzhou, Jiangsu, 215123, China
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Building 232, Santa Barbara, CA, 93106, USA
| | - Guillermo C Bazan
- Departments of Chemistry and Chemical & Biomolecular Engineering, National University of Singapore, Singapore, 119077, Singapore
| |
Collapse
|
9
|
Liang SP, Masquelier E, Morse DE, Gordon MJ, Sepunaru L. Low Voltage Voltammetry Probes Proton Dissociation Equilibria of Amino Acids and Peptides. Anal Chem 2022; 94:4948-4953. [PMID: 35290024 DOI: 10.1021/acs.analchem.1c03371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Platinum-catalyzed electrochemical reduction of dissociable protons at low potentials was used to investigate proton dissociation equilibria of freely diffusing and peptide-incorporated charged amino acids. We first demonstrate with five charged essential amino acids and their analogs that the electrochemically induced deprotonation of each amino acid occurs at distinct formal reduction potential. Moreover, the observed direct reduction for all the charged species, excluding arginine, occurs at low potentials suitable for investigation under aqueous conditions (-0.4 to -0.9 V vs Ag/AgCl). The direct proton reduction was resolved via deconvolution of the observed differential pulse voltammogram (DPV) from background hydronium reduction and water electrolysis. A linear correlation was found between the formal reduction potentials and the pKa values of the dissociable protons hosted by various molecular moieties in the amino acids and their analogs and further verified with tripeptides. DPV of poly(l-lysine) decamer (Lys10) distinctively resolved the pKa values of the amino groups in the side chains and N-terminus, at a resolution not possible by conventional acid-base titration. This work demonstrates selective electrochemical titration of dissociable protons in charged amino acids in the free state and as residues in biomolecules, as well as the utility of DPV to indirectly interrogate local electrostatic environments that are essential to the stability and function of biomolecules.
Collapse
Affiliation(s)
- Sheng-Ping Liang
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Eloise Masquelier
- Materials Department, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Daniel E Morse
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California 93106, United States.,Institute of Collaborative Biotechnologies, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Michael J Gordon
- Institute of Collaborative Biotechnologies, University of California, Santa Barbara, Santa Barbara, California 93106, United States.,Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| |
Collapse
|
10
|
Abstract
Electrochemical aptamer-based (EAB) sensors encompass the only biosensor approach yet reported that is simultaneously: (1) independent of the chemical or enzymatic reactivity of its target, rendering it general; (2) continuous and real-time; and (3) selective enough to deploy in situ in the living body. Consistent with this, in vivo EAB sensors supporting the seconds-resolved, real-time measurement of multiple drugs and metabolites have been reported, suggesting the approach may prove of value in biomedical research and the diagnosis, treatment, and monitoring of disease. However, to apply these devices in long-duration animal models, much less in human patients, requires that they be free of any significant pathogen load. Thus motivated, here we have characterized the compatibility of EAB sensors with standard sterilization and high-level disinfection techniques. Doing so, we find that, while many lead to significant sensor degradation, treatment with CIDEX OPA (0.55% ortho-phthalaldehyde) leads to effective disinfection without causing any detectable loss in sensor performance.
Collapse
Affiliation(s)
- Julia Chung
- Interdepartmental Program in Biomedical Science and Engineering, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| | - Kevin W. Plaxco
- Interdepartmental Program in Biomedical Science and Engineering, University of California at Santa Barbara, Santa Barbara, California 93106, USA
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, USA
| |
Collapse
|
11
|
Masquelier E, Liang SP, Sepunaru L, Morse DE, Gordon MJ. Reversible electrochemical triggering and optical interrogation of polylysine α-helix formation. Bioelectrochemistry 2021; 144:108007. [PMID: 34871847 DOI: 10.1016/j.bioelechem.2021.108007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 11/30/2022]
Abstract
Reversible electrochemical triggering of the random coil to α-helix conformational transition of polylysine (Lys10, Lys20, Lys50) was accomplished at a Pt electrode at potentials < |1| V vs. Ag/AgCl. Direct electroreduction of the N-terminus vs ε-amino groups in Lys sidechains, as well as hydronium reduction and electrolysis, could be easily distinguished and deconvolved using differential pulse voltammetry. Electrochemistry was coupled with in situ UV absorbance and circular dichroism spectroscopies to dynamically follow the evolution of α-helix formation at different potentials. Isotope experiments in H2O vs. D2O unequivocally confirm that direct electroreduction of ε-NH3+/ND3+ groups in Lys sidechains, rather than electrochemically generated pH gradient-induced deprotonation, leads to subsequent α-helix formation. The site-selective electrochemistry and optical methodologies presented herein can be generalized and extended to interrogate other protonation-sensitive biomolecular systems, and potentially provide access to early intermediates and control over the dynamic structural evolution of peptides and proteins.
Collapse
Affiliation(s)
- Eloise Masquelier
- Materials Department, University of California, Santa Barbara, CA, United States
| | - Sheng-Ping Liang
- Dept. Of Chemistry and Biochemistry, University of California, Santa Barbara, CA, United States
| | - Lior Sepunaru
- Dept. Of Chemistry and Biochemistry, University of California, Santa Barbara, CA, United States
| | - Daniel E Morse
- Dept. Of Molecular, Cellular and Development Biology, University of California, Santa Barbara, CA, United States; Institue for Collaborative Biotechnologies, University of California, Santa Barbara, CA, United States
| | - Michael J Gordon
- Dept. Of Chemical Engineering, University of California, Santa Barbara, CA, United States; Institue for Collaborative Biotechnologies, University of California, Santa Barbara, CA, United States.
| |
Collapse
|
12
|
Chung J, Hertler P, Plaxco KW, Sepunaru L. Catalytic Interruption Mitigates Edge Effects in the Characterization of Heterogeneous, Insulating Nanoparticles. J Am Chem Soc 2021; 143:18888-18898. [PMID: 34735140 DOI: 10.1021/jacs.1c04971] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Blocking electrochemistry, a subfield of nanochemistry, enables nondestructive, in situ measurement of the concentration, size, and size heterogeneity of highly dilute, nanometer-scale materials. This approach, in which the adsorptive impact of individual particles on a microelectrode prevents charge exchange with a freely diffusing electroactive redox mediator, has expanded the scope of electrochemistry to the study of redox-inert materials. A limitation, however, remains: inhomogeneous current fluxes associated with enhanced mass transfer occurring at the edges of planar microelectrodes confound the relationship between the size of the impacting particle and the signal it generates. These "edge effects" lead to the overestimation of size heterogeneity and, thus, poor sample characterization. In response, we demonstrate here the ability of catalytic current amplification (EC') to reduce this problem, an effect we term "electrocatalytic interruption". Specifically, we show that the increase in mass transport produced by a coupled chemical reaction significantly mitigates edge effects, returning estimated particle size distributions much closer to those observed using ex situ electron microscopy. In parallel, electrocatalytic interruption enhances the signal observed from individual particles, enabling the detection of particles significantly smaller than is possible via conventional blocking electrochemistry. Finite element simulations indicate that the rapid chemical kinetics created by this approach contributes to the amplification of the electronic signal to restore analytical precision and reliably detect and characterize the heterogeneity of nanoscale electro-inactive materials.
Collapse
Affiliation(s)
- Julia Chung
- Interdepartmental Program in Biomolecular Science and Engineering, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| | - Phoebe Hertler
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| | - Kevin W Plaxco
- Interdepartmental Program in Biomolecular Science and Engineering, University of California at Santa Barbara, Santa Barbara, California 93106, United States.,Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| |
Collapse
|
13
|
Barrett JA, Li Z, Garcia JV, Wein E, Zheng D, Hunt C, Ngo L, Sepunaru L, Iretskii AV, Ford PC. Redox-mediated carbon monoxide release from a manganese carbonyl-implications for physiological CO delivery by CO releasing moieties. R Soc Open Sci 2021; 8:211022. [PMID: 34804570 PMCID: PMC8580448 DOI: 10.1098/rsos.211022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 10/07/2021] [Indexed: 05/05/2023]
Abstract
The dynamics of hydrogen peroxide reactions with metal carbonyls have received little attention. Given reports that therapeutic levels of carbon monoxide are released in hypoxic tumour cells upon manganese carbonyls reactions with endogenous H2O2, it is critical to assess the underlying CO release mechanism(s). In this context, a quantitative mechanistic investigation of the H2O2 oxidation of the water-soluble model complex fac-[Mn(CO)3(Br)(bpCO2)]2-, (A, bpCO2 2- = 2,2'-bipyridine-4,4'-dicarboxylate dianion) was undertaken under physiologically relevant conditions. Characterizing such pathways is essential to evaluating the viability of redox-mediated CO release as an anti-cancer strategy. The present experimental studies demonstrate that approximately 2.5 equivalents of CO are released upon H2O2 oxidation of A via pH-dependent kinetics that are first-order both in [A] and in [H2O2]. Density functional calculations were used to evaluate the key intermediates in the proposed reaction mechanisms. These pathways are discussed in terms of their relevance to physiological CO delivery by carbon monoxide releasing moieties.
Collapse
Affiliation(s)
- Jacob A. Barrett
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Zhi Li
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - John V. Garcia
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Emily Wein
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Dongyun Zheng
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Camden Hunt
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Loc Ngo
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| | - Alexei V. Iretskii
- Department of Chemistry and Environmental Sciences, Lake Superior State University, Sault Sainte Marie, MI 49783, USA
| | - Peter C. Ford
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, USA
| |
Collapse
|
14
|
Roehrich B, Liu EZ, Silverstein R, Sepunaru L. Detection and Characterization of Single Particles by Electrochemical Impedance Spectroscopy. J Phys Chem Lett 2021; 12:9748-9753. [PMID: 34591489 DOI: 10.1021/acs.jpclett.1c02822] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We present an electrochemical impedance spectroscopy (EIS) technique that can detect and characterize single particles as they collide with an electrode in solution. This extension of single-particle electrochemistry offers more information than typical amperometric single-entity measurements, as EIS can isolate concurrent capacitive, resistive, and diffusional processes on the basis of their time scales. Using a simple model system, we show that time-resolved EIS can detect individual polystyrene particles that stochastically collide with an electrode. Discrete changes are observed in various equivalent circuit elements, corresponding to the physical properties of the single particles. The advantages of EIS are leveraged to separate kinetic and diffusional processes, enabling enhanced precision in measurements of the size of the particles. In a broader context, the frequency analysis and single-object resolution afforded by this technique can provide valuable insights into single pseudocapacitive microparticles, electrocatalysts, and other energy-relevant materials.
Collapse
Affiliation(s)
- Brian Roehrich
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106-9510, United States
| | - Eric Z Liu
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106-9510, United States
| | - Ravit Silverstein
- Materials Department, University of California, Santa Barbara, Santa Barbara, California 93117, United States
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106-9510, United States
| |
Collapse
|
15
|
Nikolaev A, Lu Z, Chakraborty A, Sepunaru L, de Alaniz JR. Interconvertible Living Radical and Cationic Polymerization using a Dual Photoelectrochemical Catalyst. J Am Chem Soc 2021; 143:12278-12285. [PMID: 34314165 DOI: 10.1021/jacs.1c05431] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The necessity of well-tuned reactivity for successful controlled polymer synthesis often comes with the price of limited monomer substrate scope. We demonstrate here the on-demand interconversion between living radical and cationic polymerization using two orthogonal stimuli and a dual responsive single catalyst. The dual photo- and electrochemical reactivity of 10-phenylphenothiazine catalyst provides control of the polymer's molar mass and composition by orthogonally activating the common dormant species toward two distinct chemical routes. This enables the synthesis of copolymer chains that consist of radically and cationically polymerized segments where the length of each block is controlled by the duration of the stimulus exposure. By alternating the application of photochemical and electrochemical stimuli, the on-demand incorporation of acrylates and vinyl ethers is achieved without compromising the end-group fidelity or dispersity of the formed polymer. The results provide a proof-of-concept for the ability to substantially extend substrate scope for block copolymer synthesis under mild, metal-free conditions through the use of a single, dual reactive catalyst.
Collapse
Affiliation(s)
- Andrei Nikolaev
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| | - Zhipeng Lu
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| | - Arunavo Chakraborty
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| | - Javier Read de Alaniz
- Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106, United States
| |
Collapse
|
16
|
Liang SP, Levenson R, Malady B, Gordon MJ, Morse DE, Sepunaru L. Electrochemistry as a surrogate for protein phosphorylation: voltage-controlled assembly of reflectin A1. J R Soc Interface 2020; 17:20200774. [PMID: 33259748 DOI: 10.1098/rsif.2020.0774] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Phosphorylation is among the most widely distributed mechanisms regulating the tunable structure and function of proteins in response to neuronal, hormonal and environmental signals. We demonstrate here that the low-voltage electrochemical reduction of histidine residues in reflectin A1, a protein that mediates the neuronal fine-tuning of colour reflected from skin cells for camouflage and communication in squids, acts as an in vitro surrogate for phosphorylation in vivo, driving the assembly previously shown to regulate its function. Using micro-drop voltammetry and a newly designed electrochemical cell integrated with an instrument measuring dynamic light scattering, we demonstrate selective reduction of the imidazolium side chains of histidine in monomers, oligopeptides and this complex protein in solution. The formal reduction potential of imidazolium proves readily distinguishable from those of hydronium and primary amines, allowing unequivocal confirmation of the direct and energetically selective deprotonation of histidine in the protein. The resulting 'electro-assembly' provides a new approach to probe, understand, and control the mechanisms that dynamically tune protein structure and function in normal physiology and disease. With its abilities to serve as a surrogate for phosphorylation and other mechanisms of charge neutralization, and to potentially isolate early intermediates in protein assembly, this method may be useful for analysing never-before-seen early intermediates in the phosphorylation-driven assembly of other proteins in normal physiology and disease.
Collapse
Affiliation(s)
- Sheng-Ping Liang
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Building 232, Santa Barbara, CA 93106-9510, USA
| | - Robert Levenson
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106-9625, USA.,Soka University of America, Aliso Viejo, CA 92656, USA
| | - Brandon Malady
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106-9625, USA
| | - Michael J Gordon
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106-5080, USA.,Institute for Collaborative Biotechnologies, University of California, Santa Barbara, CA 93106-5100, USA
| | - Daniel E Morse
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106-9625, USA.,Institute for Collaborative Biotechnologies, University of California, Santa Barbara, CA 93106-5100, USA
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Building 232, Santa Barbara, CA 93106-9510, USA
| |
Collapse
|
17
|
|
18
|
Roehrich B, Sepunaru L. Nanoimpacts at Active and Partially Active Electrodes: Insights and Limitations. Angew Chem Int Ed Engl 2020; 59:19184-19192. [PMID: 32745310 DOI: 10.1002/anie.202007148] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 07/31/2020] [Indexed: 11/08/2022]
Abstract
While the electrochemical nanoimpact technique has recently emerged as a method of studying single entities, it is limited by requirement of a catalytically active particle impacting an inert electrode. We show that an active particle-active electrode can provide mechanistic insight into electrochemical reactions. When an individual Pt electrocatalyst adsorbs to the surface of a partially active electrode, further reduction of electrode-produced species can proceed on the nanocatalyst. Current transients obtained during hydrogen evolution allow simultaneous measurement of the Pt catalyst over different length scales, size dependency suggests H atom intercalation as a catalytic deactivation mechanism. Although results show that outer-sphere redox probes are unproductive for particle characterization, the breadth of inner-sphere electrochemical reactions makes this a promising method for understanding the properties of catalytic nanomaterials, one at a time.
Collapse
Affiliation(s)
- Brian Roehrich
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Building 232, Santa Barbara, CA, 93106, USA
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Building 232, Santa Barbara, CA, 93106, USA
| |
Collapse
|
19
|
Affiliation(s)
- Brian Roehrich
- Department of Chemistry and Biochemistry University of California Santa Barbara, Building 232 Santa Barbara CA 93106 USA
| | - Lior Sepunaru
- Department of Chemistry and Biochemistry University of California Santa Barbara, Building 232 Santa Barbara CA 93106 USA
| |
Collapse
|
20
|
Abstract
Dynamic fluctuations of the catalytic ability of single catalase enzymes toward hydrogen peroxide decomposition are observed via the nanoimpact technique. The electrochemical signals of single enzymes show that the catalytic ability of single enzymes can temporarily be much higher than expected from the classical, time-averaged Michaelis-Menten description. By combination of experimental data with a new theoretical model, we interpret the unusual enhancement of the single catalase signal and find that single catalases show large fluctuations of the catalytic ability.
Collapse
Affiliation(s)
- Chuhong Lin
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory , Oxford University , South Parks Road , Oxford OX1 3QZ , United Kingdom
| | - Lior Sepunaru
- Department of Chemistry & Biochemistry , University of California Santa Barbara , Santa Barbara , California 93106 , United States
| | - Enno Kätelhön
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory , Oxford University , South Parks Road , Oxford OX1 3QZ , United Kingdom
| | - Richard G Compton
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory , Oxford University , South Parks Road , Oxford OX1 3QZ , United Kingdom
| |
Collapse
|
21
|
Lin C, Kätelhön E, Sepunaru L, Compton RG. Understanding single enzyme activity via the nano-impact technique. Chem Sci 2017; 8:6423-6432. [PMID: 29163928 PMCID: PMC5632796 DOI: 10.1039/c7sc02084h] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 07/17/2017] [Indexed: 12/11/2022] Open
Abstract
The electrochemical detection and characterisation of individual enzymes via the nano-impact technique is predicted.
To evaluate the possible detection of single enzyme activity via electrochemical methods, a combined finite difference and random walk simulation is used to model individual enzyme-electrode collisions where such events are monitored amperometrically via the measurement of products formed by the enzyme in solution. It is found that the observed signal is highly sensitive to both the enzyme turnover number, the size of the electrode and the bandwidth of the electronics. Taking single catalase impacts as an example, simulation results are compared with experimental data. Our work shows the requirement for the detection of electrochemically active product formed by individual enzymes and gives guidance for the design of experiments.
Collapse
Affiliation(s)
- Chuhong Lin
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , Oxford University , South Parks Road , Oxford OX1 3QZ , UK . ; ; Tel: +44 (0)1865 275957
| | - Enno Kätelhön
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , Oxford University , South Parks Road , Oxford OX1 3QZ , UK . ; ; Tel: +44 (0)1865 275957
| | - Lior Sepunaru
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , Oxford University , South Parks Road , Oxford OX1 3QZ , UK . ; ; Tel: +44 (0)1865 275957
| | - Richard G Compton
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , Oxford University , South Parks Road , Oxford OX1 3QZ , UK . ; ; Tel: +44 (0)1865 275957
| |
Collapse
|
22
|
Kätelhön E, Sepunaru L, Karyakin AA, Compton RG. Reply to Comment on “Can Nanoimpacts Detect Single-Enzyme Activity? Theoretical Considerations and an Experimental Study of Catalase Impacts”. ACS Catal 2017. [DOI: 10.1021/acscatal.7b00994] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Enno Kätelhön
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Lior Sepunaru
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Arkady A. Karyakin
- Chemistry
Faculty, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Richard G. Compton
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom
| |
Collapse
|
23
|
Chan C, Sepunaru L, Sokolov SV, Kätelhön E, Young NP, Compton RG. Catalytic activity of catalase-silica nanoparticle hybrids: from ensemble to individual entity activity. Chem Sci 2017; 8:2303-2308. [PMID: 28451333 PMCID: PMC5363393 DOI: 10.1039/c6sc04921d] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 12/14/2016] [Indexed: 01/01/2023] Open
Abstract
We demonstrate the electrochemical detection and characterization of individual nanoparticle–enzyme hybrids.
We demonstrate the electrochemical detection and characterization of individual nanoparticle–enzyme hybrids. Silica nanoparticles were functionalized with catalase enzyme and investigated spectroscopically and electrochemically. The catalytic activity of the hybrids towards hydrogen peroxide decomposition was comparable to the activity of a freely diffusing enzyme in solution, exhibiting a Michaelis–Menten constant of KM = 74 mM and a turnover number of kcat = 8 × 107 s–1 per NP. The fast turnover number of the hybrid further enabled the electrochemical detection of individual nanoparticle–enzyme hybrid via a novel method: the hydrogen peroxide substrate was generated at a microelectrode which enabled enzymatic activity exclusively within the diffusion layer of the electrode. The method is the first electrochemical approach for measuring hybrid nanoparticles, at the single entity level.
Collapse
Affiliation(s)
- Crystal Chan
- Department of Chemistry , Physical & Theoretical Chemistry Laboratory , University of Oxford , South Parks Road , Oxford OX1 3QZ , UK .
| | - Lior Sepunaru
- Department of Chemistry , Physical & Theoretical Chemistry Laboratory , University of Oxford , South Parks Road , Oxford OX1 3QZ , UK .
| | - Stanislav V Sokolov
- Department of Chemistry , Physical & Theoretical Chemistry Laboratory , University of Oxford , South Parks Road , Oxford OX1 3QZ , UK .
| | - Enno Kätelhön
- Department of Chemistry , Physical & Theoretical Chemistry Laboratory , University of Oxford , South Parks Road , Oxford OX1 3QZ , UK .
| | - Neil P Young
- Department of Materials , University of Oxford , OX1 3PH , UK
| | - Richard G Compton
- Department of Chemistry , Physical & Theoretical Chemistry Laboratory , University of Oxford , South Parks Road , Oxford OX1 3QZ , UK .
| |
Collapse
|
24
|
Zhang H, Sepunaru L, Sokolov SV, Laborda E, Batchelor-McAuley C, Compton RG. Electrochemistry of single droplets of inverse (water-in-oil) emulsions. Phys Chem Chem Phys 2017; 19:15662-15666. [DOI: 10.1039/c7cp03300a] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Single water droplet electrochemistry investigated for the first time, reveals the biphasic kinetics of ion transfer within water-in-oil emulsions.
Collapse
Affiliation(s)
- Haozhi Zhang
- Department of Chemistry
- Physical and Theoretical Chemistry Laboratory
- University of Oxford
- Oxford OX1 3QZ
- UK
| | - Lior Sepunaru
- Department of Chemistry
- Physical and Theoretical Chemistry Laboratory
- University of Oxford
- Oxford OX1 3QZ
- UK
| | - Stanislav V. Sokolov
- Department of Chemistry
- Physical and Theoretical Chemistry Laboratory
- University of Oxford
- Oxford OX1 3QZ
- UK
| | - Eduardo Laborda
- Departamento de Química Física
- Facultad de Química
- Universidad de Murcia
- 30100 Murcia
- Spain
| | | | - Richard G. Compton
- Department of Chemistry
- Physical and Theoretical Chemistry Laboratory
- University of Oxford
- Oxford OX1 3QZ
- UK
| |
Collapse
|
25
|
Kätelhön E, Sepunaru L, Karyakin AA, Compton RG. Can Nanoimpacts Detect Single-Enzyme Activity? Theoretical Considerations and an Experimental Study of Catalase Impacts. ACS Catal 2016. [DOI: 10.1021/acscatal.6b02633] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Enno Kätelhön
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Lior Sepunaru
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Arkady A. Karyakin
- Chemistry
Faculty, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Richard G. Compton
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom
| |
Collapse
|
26
|
Affiliation(s)
- Lior Sepunaru
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory; University of Oxford; South Parks Road Oxford OX1 3QZ UK
| | - Stanislav V. Sokolov
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory; University of Oxford; South Parks Road Oxford OX1 3QZ UK
| | | | - Neil P. Young
- Department of Materials; University of Oxford; OX1 3PH UK
| | - Richard G. Compton
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory; University of Oxford; South Parks Road Oxford OX1 3QZ UK
| |
Collapse
|
27
|
Sepunaru L, Sokolov SV, Holter J, Young NP, Compton RG. Electrochemical Red Blood Cell Counting: One at a Time. Angew Chem Int Ed Engl 2016; 55:9768-71. [DOI: 10.1002/anie.201605310] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Indexed: 11/05/2022]
Affiliation(s)
- Lior Sepunaru
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory; University of Oxford; South Parks Road Oxford OX1 3QZ UK
| | - Stanislav V. Sokolov
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory; University of Oxford; South Parks Road Oxford OX1 3QZ UK
| | | | - Neil P. Young
- Department of Materials; University of Oxford; OX1 3PH UK
| | - Richard G. Compton
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory; University of Oxford; South Parks Road Oxford OX1 3QZ UK
| |
Collapse
|
28
|
Sepunaru L, Plowman BJ, Sokolov SV, Young NP, Compton RG. Rapid electrochemical detection of single influenza viruses tagged with silver nanoparticles. Chem Sci 2016; 7:3892-3899. [PMID: 30155033 PMCID: PMC6013776 DOI: 10.1039/c6sc00412a] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 02/24/2016] [Indexed: 02/05/2023] Open
Abstract
Using a state of the art nano-electrochemical technique, we show that a single virus 'tagged' with silver nanoparticles can be rapidly detected in real time at the single virus level. A solution containing a low concentration of influenza virus is exposed to silver nanoparticles which are adsorbed onto the virus surface, as revealed by UV-Vis spectroscopy and transmission electron microscopy. With sufficient potential applied to a carbon electrode introduced into the solution, current spikes are observed which correspond to the oxidation of the nanoparticles decorating the virus. The frequency of the current spikes and their magnitude are linearly proportional to the virus concentration and to the surface coverage of the nanoparticles, respectively. Differences observed from single bacterium detection are discussed and a comparison with existing detection methods is made, with emphasis on the favourability of the proposed technique towards the realization of point of care test devices.
Collapse
Affiliation(s)
- Lior Sepunaru
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , Oxford University , Oxford OX1 3QZ , UK .
| | - Blake J Plowman
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , Oxford University , Oxford OX1 3QZ , UK .
| | - Stanislav V Sokolov
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , Oxford University , Oxford OX1 3QZ , UK .
| | - Neil P Young
- Department of Materials , Oxford University , Oxford OX1 3PH , UK
| | - Richard G Compton
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , Oxford University , Oxford OX1 3QZ , UK .
| |
Collapse
|
29
|
Sepunaru L, Laborda E, Compton RG. Catalase-Modified Carbon Electrodes: Persuading Oxygen To Accept Four Electrons Rather Than Two. Chemistry 2016; 22:5904-8. [PMID: 26934203 DOI: 10.1002/chem.201600692] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Indexed: 11/07/2022]
Abstract
We successfully exploited the natural highly efficient activity of an enzyme (catalase) together with carbon electrodes to produce a hybrid electrode for oxygen reduction, very appropriate for energy transformation. Carbon electrodes, in principle, are cheap but poor oxygen reduction materials, because only two-electron reduction of oxygen occurs at low potentials, whereas four-electron reduction is key for energy-transformation technology. With the immobilization of catalase on the surface, the hydrogen peroxide produced electrochemically is decomposed back to oxygen by the enzyme; the enzyme natural activity on the surface regenerates oxygen, which is further reduced by the carbon electrode with no direct electron transfer between the enzyme and the electrode. Near full four-electron reduction of oxygen is realised on a carbon electrode, which is modified with ease by a commercially available enzyme. The value of such enzyme-modified electrode for energy-transformation devices is evident.
Collapse
Affiliation(s)
- Lior Sepunaru
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, UK
| | - Eduardo Laborda
- Departamento de Química Física, Facultad de Química, Regional Campus of International Excellence, "Campus Mare Nostrum", Universidad de Murcia, 30100, Murcia, Spain
| | - Richard G Compton
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, UK.
| |
Collapse
|
30
|
Abstract
A vertical nanogap device (VND) structure comprising all-silicon contacts as electrodes for the investigation of electronic transport processes in bioelectronic systems is reported. Devices were fabricated from silicon-on-insulator substrates whose buried oxide (SiO2) layer of a few nanometers in thickness is embedded within two highly doped single crystalline silicon layers. Individual VNDs were fabricated by standard photolithography and a combination of anisotropic and selective wet etching techniques, resulting in p(+) silicon contacts, vertically separated by 4 or 8 nm, depending on the chosen buried oxide thickness. The buried oxide was selectively recess-etched with buffered hydrofluoric acid, exposing a nanogap. For verification of the devices' electrical functionality, gold nanoparticles were successfully trapped onto the nanogap electrodes' edges using AC dielectrophoresis. Subsequently, the suitability of the VND structures for transport measurements on proteins was investigated by functionalizing the devices with cytochrome c protein from solution, thereby providing non-destructive, permanent semiconducting contacts to the proteins. Current-voltage measurements performed after protein deposition exhibited an increase in the junctions' conductance of up to several orders of magnitude relative to that measured prior to cytochrome c immobilization. This increase in conductance was lost upon heating the functionalized device to above the protein's denaturation temperature (80 °C). Thus, the VND junctions allow conductance measurements which reflect the averaged electronic transport through a large number of protein molecules, contacted in parallel with permanent contacts and, for the first time, in a symmetrical Si-protein-Si configuration.
Collapse
Affiliation(s)
- Muhammed I Schukfeh
- Institut für Halbleitertechnik, TU Braunschweig, Hans-Sommer-Str. 66, D-38106 Braunschweig, Germany
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Shimizu K, Sepunaru L, Compton RG. Innovative catalyst design for the oxygen reduction reaction for fuel cells. Chem Sci 2016; 7:3364-3369. [PMID: 29997830 PMCID: PMC6007091 DOI: 10.1039/c6sc00139d] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 02/11/2016] [Indexed: 11/21/2022] Open
Abstract
A combination of chemical and electrochemical catalysis is introduced herein as a new approach to overcome one of the most challenging and persistent issues in fuel cell cathodes. Demonstrated using hematite (α-Fe2O3) nanoparticles modified glassy carbon electrode, this bifunctional fuel cell catalyst system prevails the slow kinetics of the oxygen reduction reaction by rapid heterogeneous disproportionation of hydrogen peroxide. Whilst the catalytic efficiency of glassy carbon is limited to the two-electron reduction of oxygen, modification with hematite drastically improves it to equivalent to the four-electron pathway. This is due to regeneration of the cathodic fuel through the rapid decomposition of hydrogen peroxide. The importance of such system is stressed as the formation of water rather than hydrogen peroxide is essential to maximize the energy output of the fuel cell. Cycling of oxygen reduction/regeneration boosts the activity of a low-cost catalyst to be comparable to that of platinum and concurrently reduces the risk of cell degradation.
Collapse
Affiliation(s)
- Kenichi Shimizu
- Physical and Theoretical Chemistry Laboratory , Department of Chemistry , The University of Oxford , South Parks Road , Oxford , OX1 3QZ , UK . ; ; Tel: +44 (0)1865 275 413 ; Tel: +44 (0)1865 275 957
| | - Lior Sepunaru
- Physical and Theoretical Chemistry Laboratory , Department of Chemistry , The University of Oxford , South Parks Road , Oxford , OX1 3QZ , UK . ; ; Tel: +44 (0)1865 275 413 ; Tel: +44 (0)1865 275 957
| | - Richard G Compton
- Physical and Theoretical Chemistry Laboratory , Department of Chemistry , The University of Oxford , South Parks Road , Oxford , OX1 3QZ , UK . ; ; Tel: +44 (0)1865 275 413 ; Tel: +44 (0)1865 275 957
| |
Collapse
|
32
|
Yu X, Lovrincic R, Sepunaru L, Li W, Vilan A, Pecht I, Sheves M, Cahen D. Insights into Solid-State Electron Transport through Proteins from Inelastic Tunneling Spectroscopy: The Case of Azurin. ACS Nano 2015; 9:9955-63. [PMID: 26381112 DOI: 10.1021/acsnano.5b03950] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Surprisingly efficient solid-state electron transport has recently been demonstrated through "dry" proteins (with only structural, tightly bound H2O left), suggesting proteins as promising candidates for molecular (bio)electronics. Using inelastic electron tunneling spectroscopy (IETS), we explored electron-phonon interaction in metal/protein/metal junctions, to help understand solid-state electronic transport across the redox protein azurin. To that end an oriented azurin monolayer on Au is contacted by soft Au electrodes. Characteristic vibrational modes of amide and amino acid side groups as well as of the azurin-electrode contact were observed, revealing the azurin native conformation in the junction and the critical role of side groups in the charge transport. The lack of abrupt changes in the conductance and the line shape of IETS point to far off-resonance tunneling as the dominant transport mechanism across azurin, in line with previously reported (and herein confirmed) azurin junctions. The inelastic current and hence electron-phonon interaction appear to be rather weak and comparable in magnitude with the inelastic fraction of tunneling current via alkyl chains, which may reflect the known structural rigidity of azurin.
Collapse
Affiliation(s)
| | - Robert Lovrincic
- Institute for High Frequency Technology, TU Braunschweig, and Innovationlab , Speyerer Str. 4, 69115 Heidelberg, Germany
| | | | | | | | | | | | | |
Collapse
|
33
|
Sepunaru L, Refaely-Abramson S, Lovrinčić R, Gavrilov Y, Agrawal P, Levy Y, Kronik L, Pecht I, Sheves M, Cahen D. Electronic Transport via Homopeptides: The Role of Side Chains and Secondary Structure. J Am Chem Soc 2015; 137:9617-26. [DOI: 10.1021/jacs.5b03933] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lior Sepunaru
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Sivan Refaely-Abramson
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Robert Lovrinčić
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Yulian Gavrilov
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Piyush Agrawal
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Yaakov Levy
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Leeor Kronik
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Israel Pecht
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Mordechai Sheves
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - David Cahen
- Department of Materials and Interfaces, ‡Department of Organic
Chemistry, §Department of Structural
Biology, and ∥Department of Immunology, Weizmann Institute of Science, Rehovot, 7610001, Israel
| |
Collapse
|
34
|
Sepunaru L, Tschulik K, Batchelor-McAuley C, Gavish R, Compton RG. Electrochemical detection of single E. coli bacteria labeled with silver nanoparticles. Biomater Sci 2015. [PMID: 26221841 DOI: 10.1039/c5bm00114e] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A proof-of-concept for the electrochemical detection of single Escherichia coli bacteria decorated with silver nanoparticles is reported. Impacts of bacteria with an electrode - held at a suitably oxidizing potential - lead to an accompanying burst of current with each collision event. The frequency of impacts scales with the concentration of bacteria and the charge indicates the extent of decoration.
Collapse
Affiliation(s)
- Lior Sepunaru
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, UK.
| | | | | | | | | |
Collapse
|
35
|
Amdursky N, Sepunaru L, Raichlin S, Pecht I, Sheves M, Cahen D. Electron Transfer Proteins as Electronic Conductors: Significance of the Metal and Its Binding Site in the Blue Cu Protein, Azurin. Adv Sci (Weinh) 2015; 2:1400026. [PMID: 27980928 PMCID: PMC5115354 DOI: 10.1002/advs.201400026] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 02/08/2015] [Indexed: 05/07/2023]
Abstract
Electron transfer (ET) proteins are biomolecules with specific functions, selected by evolution. As such they are attractive candidates for use in potential bioelectronic devices. The blue copper protein azurin (Az) is one of the most-studied ET proteins. Traditional spectroscopic, electrochemical, and kinetic methods employed for studying ET to/from the protein's Cu ion have been complemented more recently by studies of electrical conduction through a monolayer of Az in the solid-state, sandwiched between electrodes. As the latter type of measurement does not require involvement of a redox process, it also allows monitoring electronic transport (ETp) via redox-inactive Az-derivatives. Here, results of macroscopic ETp via redox-active and -inactive Az derivatives, i.e., Cu(II) and Cu(I)-Az, apo-Az, Co(II)-Az, Ni(II)-Az, and Zn(II)-Az are reported and compared. It is found that earlier reported temperature independence of ETp via Cu(II)-Az (from 20 K until denaturation) is unique, as ETp via all other derivatives is thermally activated at temperatures >≈200 K. Conduction via Cu(I)-Az shows unexpected temperature dependence >≈200 K, with currents decreasing at positive and increasing at negative bias. Taking all the data together we find a clear compensation effect of Az conduction around the Az denaturation temperature. This compensation can be understood by viewing the Az binding site as an electron trap, unless occupied by Cu(II), as in the native protein, with conduction of the native protein setting the upper transport efficiency limit.
Collapse
Affiliation(s)
- Nadav Amdursky
- Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel; Departments of Organic Chemistry Weizmann Institute of Science Rehovot 76100 Israel
| | - Lior Sepunaru
- Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel
| | - Sara Raichlin
- Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel; Departments of Organic Chemistry Weizmann Institute of Science Rehovot 76100 Israel
| | - Israel Pecht
- Departments of Immunology Weizmann Institute of Science Rehovot 76100 Israel
| | - Mordechai Sheves
- Departments of Organic Chemistry Weizmann Institute of Science Rehovot 76100 Israel
| | - David Cahen
- Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel
| |
Collapse
|
36
|
Amdursky N, Marchak D, Sepunaru L, Pecht I, Sheves M, Cahen D. Electronic transport via proteins. Adv Mater 2014; 26:7142-61. [PMID: 25256438 DOI: 10.1002/adma.201402304] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 08/07/2014] [Indexed: 05/25/2023]
Abstract
A central vision in molecular electronics is the creation of devices with functional molecular components that may provide unique properties. Proteins are attractive candidates for this purpose, as they have specific physical (optical, electrical) and chemical (selective binding, self-assembly) functions and offer a myriad of possibilities for (bio-)chemical modification. This Progress Report focuses on proteins as potential building components for future bioelectronic devices as they are quite efficient electronic conductors, compared with saturated organic molecules. The report addresses several questions: how general is this behavior; how does protein conduction compare with that of saturated and conjugated molecules; and what mechanisms enable efficient conduction across these large molecules? To answer these questions results of nanometer-scale and macroscopic electronic transport measurements across a range of organic molecules and proteins are compiled and analyzed, from single/few molecules to large molecular ensembles, and the influence of measurement methods on the results is considered. Generalizing, it is found that proteins conduct better than saturated molecules, and somewhat poorer than conjugated molecules. Significantly, the presence of cofactors (redox-active or conjugated) in the protein enhances their conduction, but without an obvious advantage for natural electron transfer proteins. Most likely, the conduction mechanisms are hopping (at higher temperatures) and tunneling (below ca. 150-200 K).
Collapse
Affiliation(s)
- Nadav Amdursky
- Dept. of Materials & Interfaces, Weizmann Institute of Science, Rehovot, 76305, Israel
| | | | | | | | | | | |
Collapse
|
37
|
Li W, Sepunaru L, Amdursky N, Cohen SR, Pecht I, Sheves M, Cahen D. Temperature and force dependence of nanoscale electron transport via the Cu protein azurin. ACS Nano 2012; 6:10816-10824. [PMID: 23136937 DOI: 10.1021/nn3041705] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Solid-state electron transport (ETp) via a monolayer of immobilized azurin (Az) was examined by conducting probe atomic force microscopy (CP-AFM), as a function of both temperature (248-373K) and applied tip force (6-15 nN). At low forces, ETp via holo-Az (with Cu(2+)) is temperature-independent, but thermally activated via the Cu-depleted form of Az, apo-Az. While this observation agrees with those of macroscopic-scale measurements, we find that for holo-Az the mechanism of ETp at high temperatures changes upon an increase in the force applied by the tip to the proteins; namely, above 310 K and forces >6 nN ETp becomes thermally activated. This is in contrast to apo-Az, where increasing applied force causes only small monotonic increases in currents due to decreased electrode separation. The distinct ETp temperature dependence of holo- and apo-Az is assigned to a difference in structural response to pressure between the two protein forms. An important implication of these CP-AFM results (of measurements over a significant temperature range) is that for reliable ETp measurements on flexible macromolecules, such as proteins, the pressure applied during the measurements should be controlled or at least monitored.
Collapse
Affiliation(s)
- Wenjie Li
- Department of Materials & Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | | | | | | | | | | |
Collapse
|
38
|
Sepunaru L, Friedman N, Pecht I, Sheves M, Cahen D. Temperature-Dependent Solid-State Electron Transport through Bacteriorhodopsin: Experimental Evidence for Multiple Transport Paths through Proteins. J Am Chem Soc 2012; 134:4169-76. [DOI: 10.1021/ja2097139] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Lior Sepunaru
- Departments
of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100,
Israel
| | - Noga Friedman
- Departments
of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100,
Israel
| | - Israel Pecht
- Departments
of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100,
Israel
| | - Mordechai Sheves
- Departments
of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100,
Israel
| | - David Cahen
- Departments
of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100,
Israel
| |
Collapse
|
39
|
Sepunaru L, Pecht I, Sheves M, Cahen D. Solid-State Electron Transport across Azurin: From a Temperature-Independent to a Temperature-Activated Mechanism. J Am Chem Soc 2011; 133:2421-3. [DOI: 10.1021/ja109989f] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lior Sepunaru
- Departments of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100, Israel
| | - Israel Pecht
- Departments of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100, Israel
| | - Mordechai Sheves
- Departments of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100, Israel
| | - David Cahen
- Departments of Materials and Interfaces, ‡Organic Chemistry, and §Immunology, Weizmann Institute of Science, POB 26, Rehovot 76100, Israel
| |
Collapse
|
40
|
Ron I, Sepunaru L, Itzhakov S, Belenkova T, Friedman N, Pecht I, Sheves M, Cahen D. Proteins as electronic materials: electron transport through solid-state protein monolayer junctions. J Am Chem Soc 2010; 132:4131-40. [PMID: 20210314 DOI: 10.1021/ja907328r] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron transfer (ET) through proteins, a fundamental element of many biochemical reactions, is studied intensively in aqueous solutions. Over the past decade, attempts were made to integrate proteins into solid-state junctions in order to study their electronic conductance properties. Most such studies to date were conducted with one or very few molecules in the junction, using scanning probe techniques. Here we present the high-yield, reproducible preparation of large-area monolayer junctions, assembled on a Si platform, of proteins of three different families: azurin (Az), a blue-copper ET protein, bacteriorhodopsin (bR), a membrane protein-chromophore complex with a proton pumping function, and bovine serum albumin (BSA). We achieve highly reproducible electrical current measurements with these three types of monolayers using appropriate top electrodes. Notably, the current-voltage (I-V) measurements on such junctions show relatively minor differences between Az and bR, even though the latter lacks any known ET function. Electron Transport (ETp) across both Az and bR is much more efficient than across BSA, but even for the latter the measured currents are higher than those through a monolayer of organic, C18 alkyl chains that is about half as wide, therefore suggesting transport mechanism(s) different from the often considered coherent mechanism. Our results show that the employed proteins maintain their conformation under these conditions. The relatively efficient ETp through these proteins opens up possibilities for using such biomolecules as current-carrying elements in solid-state electronic devices.
Collapse
Affiliation(s)
- Izhar Ron
- Departments of Materials and Interfaces, Weizmann Institute of Science, POB 26, Rehovot 76100, Israel
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Sepunaru L, Tsimberov I, Forolov L, Carmeli C, Carmeli I, Rosenwaks Y. Picosecond electron transfer from photosynthetic reaction center protein to GaAs. Nano Lett 2009; 9:2751-2755. [PMID: 19527017 DOI: 10.1021/nl901262h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
An extremely fast electron transfer through an electronically coupled junction between covalently bound oriented photosynthetic reaction center protein photosystem I (PS I) and n-GaAs was measured by time-resolved photoluminescence. It was found that the n-GaAs band edge luminescence intensity increased by a factor of 2, and the fast exponential decay constant was increased by a factor of 2.6 following the PS I self-assembly. We attribute this to picosecond electron transfer from the PS I to the n-GaAs surface states.
Collapse
Affiliation(s)
- Lior Sepunaru
- Department of Biochemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | | | | | | | | | | |
Collapse
|