The Single-Molecule Conductance and Electrochemical Electron-Transfer Rate Are Related by a Power Law

Wierzbiński, Emil; Venkatramani, Ravindra; Davis, Kathryn L.; Bezer, Silvia; Kong, Jing; Xing, Yangjun; Borguet, Eric; Achim, Catalina; Beratan, David N.; Waldeck, David H.

doi:10.1021/nn401321k

Cited by 73 publications

(103 citation statements)

References 58 publications

(172 reference statements)

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“…Thus, it is very likely that the Hg drop contacts in each case only the most exposed amino acids. The lack of correlation between the measured current densities and the calculated electrode separation distances (protein monolayer widths) is in contrast to results obtained from ETp studies via peptides (35)(36)(37) and peptide nucleic acids (38). However, none of the latter molecules contain an internal cofactor, like CytC and Az do.…”

Section: Discussioncontrasting

confidence: 73%

Solid-state electron transport via cytochrome c depends on electronic coupling to electrodes and across the protein

Amdursky

Ferber

Bortolotti

et al. 2014

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

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Electronic coupling to electrodes, Γ, as well as that across the examined molecules, H, is critical for solid-state electron transport (ETp) across proteins. Assessing the importance of each of these couplings helps to understand the mechanism of electron flow across molecules. We provide here experimental evidence for the importance of both couplings for solid-state ETp across the electron-mediating protein cytochrome c (CytC), measured in a monolayer configuration. Currents via CytC are temperature-independent between 30 and ∼130 K, consistent with tunneling by superexchange, and thermally activated at higher temperatures, ascribed to steady-state hopping. Covalent protein-electrode binding significantly increases Γ, as currents across CytC mutants, bound covalently to the electrode via a cysteine thiolate, are higher than those through electrostatically adsorbed CytC. Covalent binding also reduces the thermal activation energy, E a , of the ETp by more than a factor of two. The importance of H was examined by using a series of seven CytC mutants with cysteine residues at different surface positions, yielding distinct electrode-protein(-heme) orientations and separation distances. We find that, in general, mutants with electrode-proximal heme have lower E a values (from high-temperature data) and higher conductance at low temperatures (in the temperatureindependent regime) than those with a distal heme. We conclude that ETp across these mutants depends on the distance between the heme group and the top or bottom electrode, rather than on the total separation distance between electrodes (protein width).bioelectronics | temperature dependence | protein conduction

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Section: Discussioncontrasting

confidence: 73%

Solid-state electron transport via cytochrome c depends on electronic coupling to electrodes and across the protein

Amdursky

Ferber

Bortolotti

et al. 2014

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

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“…30,39 Varying the concentration of the nucleic acid duplexes on the surface indicated that a higher molecular coverage causes these fluctuations in the current response to 8 occur more frequently, supporting the interpretation that two molecules in the junction cause the fluctuations. 31,[41][42] Although only two conductance modes are observed for some of the systems, the nomenclature of 'high' and 'medium' conductance modes is kept for consistency with published data on thiol linkers. This transition could reflect a change in the binding of the linker groups to the gold substrate or the partial unraveling of the nucleic acid strand.…”

Section: Conductance Measurementsmentioning

confidence: 99%

“…At later times, the higher conductance mode transitions to a much lower conductance regime with a more stable current response. 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 9 in each case with propylthiol linker groups. 40 The latter possibility is less likely, however, as single strand molecules give much lower currents (<100 pA) than the ones observed here (5 to 10 nA for the lower conductance).…”

Section: Conductance Measurementsmentioning

confidence: 99%

“…27 The experimental observation of larger electrochemical rate constants for aeg-PNA as compared to those for γ-PNA was rationalized as arising from an increase in the energy level broadening of the hole mediating superexchange states with the increase in duplex flexibility; or, alternatively, arising from the ability of the more flexible aeg-PNA duplexes to access conformations with higher electronic couplings more often than do γ-PNA duplexes. 30 Because the electron transfer rate is directly related to the electrical conductance, 31 it seems plausible that such effects can cause differences between the single molecule conductance of nucleic acid duplexes. The dependence of electron transfer rates on structural fluctuations was also observed in studies on DNA/LNA hybrids 29 and reported for DNA duplexes at different temperatures.…”

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confidence: 99%

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Effects of the Backbone and Chemical Linker on the Molecular Conductance of Nucleic Acid Duplexes

et al. 2017

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Scanning tunneling microscope break junction measurements are used to examine how the molecular conductance of nucleic acids depends on the composition of their backbone and the linker group to the electrodes. Molecular conductances of 10 base pair long homoduplexes of DNA, aeg-PNA, γ-PNA, and a heteroduplex of DNA/aeg-PNA with identical nucleobase sequence were measured. The molecular conductance was found to vary by 12 to 13 times with the change in backbone. Computational studies show that the molecular conductance differences between nucleic acids of different backbones correlate with differences in backbone structural flexibility. The molecular conductance was also measured for duplexes connected to the electrode through two different linkers, one directly to the backbone and one directly to the nucleobase stack. While the linker causes an order-of-magnitude increase in the overall conductance for a particular duplex, the differences in the electrical conductance with backbone composition are preserved. The highest molecular conductance value, 0.06G, was measured for aeg-PNA duplexes with a base stack linker. These findings reveal an important new strategy for creating longer and more complex electroactive, nucleic acid assemblies.

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“…[49][50][51] As an alternative to DNA, peptide nucleic acid (PNA) strands present certain advantages for long-range hole hopping. [58][59][60][61] The smaller helical twist of PNA, in comparison with DNA, improves the electronic coupling between neighboring bases. 58 Furthermore, PNA derivatives are not acids (despite the name) and they do not contain ionic charges along their backbones.…”

Section: Ct Molecular Electrets: Practical Ideas From Structural Biologymentioning

confidence: 99%

Bioinspired molecular electrets: bottom-up approach to energy materials and applications

2015

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Abstract. The diversity of life on Earth is made possible through an immense variety of proteins that stems from less than a couple of dozen native amino acids. Is it possible to achieve similar engineering freedom and precision to design electronic materials? What if a handful of nonnative residues with a wide range of characteristics could be rationally placed in sequences to form organic macromolecules with specifically targeted properties and functionalities? Referred to as molecular electrets, dipolar oligomers and polymers composed of non-native aromatic beta-amino acids, anthranilamides (Aa) provide venues for pursuing such possibilities. The electret molecular dipoles play a crucial role in rectifying charge transfer, e.g., enhancing charge separation and suppressing undesired charge recombination, which is essential for photovoltaics, photocatalysis, and other solar-energy applications. A set of a few Aa residues can serve as building blocks for molecular electrets with widely diverse electronic properties, presenting venues for bottom-up designs. We demonstrate how three substituents and structural permutations within an Aa residue widely alter its reduction potential. Paradigms of diversity in electronic properties, originating from a few changes within a basic molecular structure, illustrate the promising potentials of biological inspiration for energy science and engineering.

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The Single-Molecule Conductance and Electrochemical Electron-Transfer Rate Are Related by a Power Law

Cited by 73 publications

References 58 publications

Solid-state electron transport via cytochrome c depends on electronic coupling to electrodes and across the protein

Solid-state electron transport via cytochrome c depends on electronic coupling to electrodes and across the protein

Effects of the Backbone and Chemical Linker on the Molecular Conductance of Nucleic Acid Duplexes

Bioinspired molecular electrets: bottom-up approach to energy materials and applications

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