Biological electron tunneling through native protein media

Moser, Christopher C.; Page, Christopher; Chen, X.; Dutton, P. Leslie

doi:10.1007/s007750050149

Cited by 58 publications

(43 citation statements)

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“…In situ STM of redox metalloproteins, with low-lying intermediate transition metal redox levels, holds new perspectives for long-range ET in metalloproteins and for conductivity changes induced by substrate binding such as that observed, for example, for the four-copper redox enzyme, ascorbate oxidase, in aqueous solution (57). The perspectives would extend to the elusive distinction between superexchange, coherent, and sequential ET mechanisms often discussed in ET science (1)(2)(3)(4)(5)(6)(7). Such data are not available presently but are in demand in view of the subtleties associated with the potential control and distribution in the gap region and with problems associated with robust layer configurations for electron exchange between metallic electrodes and adsorbed proteins (58).…”

mentioning

confidence: 99%

“…Progress has rested on synthetic donor-acceptor molecules (1-3), metalloproteins (2,4,6,7), and on new electrochemical systems in which electrons are brought to tunnel across well characterized, self-assembled films (8,9). These achievements have prompted new theoretical efforts with notions such as directional tunneling along chemical bond networks (10), fluctuating tunnel barriers (11,12), coherent and resonance ET (13), and self-consistent electronic-vibrational interaction (11).…”

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confidence: 99%

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An approach to long-range electron transfer mechanisms in metalloproteins: In situ scanning tunneling microscopy with submolecular resolution

Friis

Andersen

Kharkats

et al. 1999

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

130

106

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In situ scanning tunneling microscopy (STM) of redox molecules, in aqueous solution, shows interesting analogies and differences compared with interfacial electrochemical electron transfer ( Molecular long-range electron transfer (ET) in solid phases or liquid solution, in which the ET distance exceeds the structural extension of the donor and acceptor, has been in focus over the last decade and a half (1-5). Progress has rested on synthetic donor-acceptor molecules (1-3), metalloproteins (2, 4, 6, 7), and on new electrochemical systems in which electrons are brought to tunnel across well characterized, self-assembled films (8, 9). These achievements have prompted new theoretical efforts with notions such as directional tunneling along chemical bond networks (10), fluctuating tunnel barriers (11, 12), coherent and resonance ET (13), and self-consistent electronic-vibrational interaction (11).In a parallel development, scanning tunneling and atomic force microscopy (STM and AFM, respectively) have opened exciting new perspectives for mapping molecular adsorbate patterns (14, 15). The primary basis for adsorption patterns in vacuum or air is imaging of small and intermediate-size adsorbate molecules with molecular and submolecular resolution (14-17), combined with theoretical frames for tunneling through adsorbate molecules based on different methodologies (17-21). There are also reported experimental approaches to functional mapping of intermediate-size molecules, most prominently in the form of correlations between the tunnel current and the bias voltage. Target adsorbates for ex situ STM imaging have been, for example, benzene (22, 23), methylazulenes (17, 24), C 60 (25), alkyl and aryl thiolates (17,21,(26)(27)(28), and transition metal phthalocyanins (29) on highly oriented pyrolytic graphite or crystalline surfaces of electronically ''soft'' metals compatible with the adsorbates. STM imaging at the solid͞air interface to molecular and occasionally submolecular resolution also has been extended to biological macromolecules including DNA (30) and a number of redox and nonredox proteins (for an overview, see ref. 31). Functional properties addressed particularly have been the electrical potential distribution and conductivity patterns of the tunnel gap (21, 27-29), resonance tunneling via suitable highest occupied molecular orbitals, lowest unoccupied molecular orbitals, or (transition metal) redox levels (17-21), and the notion of orbital-specific mediation of the tunnel current (29).Combination of STM with concepts of long-range ET in chemical and, particularly, metalloprotein systems must, however, give explicit attention to the fact that the natural medium for most chemical and biological reactivity is aqueous solution. Extension of STM͞AFM to aqueous solution (in situ STM͞ AFM) is established (32, 33) but has raised issues related to adsorbate immobilization, ultrapure solutions, tip coating, independent tip and substrate potential control (32-34), and the fundamental STM and AFM phenomena. In situ...

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mentioning

confidence: 99%

mentioning

confidence: 99%

An approach to long-range electron transfer mechanisms in metalloproteins: In situ scanning tunneling microscopy with submolecular resolution

Friis

Andersen

Kharkats

et al. 1999

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

130

106

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“…The alternative explanation that in the H35F/N42C/M64E dimer the Glu64 unit in the interface is deprotonated and therefore intermolecular association is slowed down, is less likely since at the employed pH* of 4.5 the ese rate of the monomer is not yet affected by deprotonation of Glu64. [13] According to Dutton et al, the rate of ET, k ET , between two redox centres separated by a homogeneous medium is given by Equation (1), [17,18] in which ρ denotes the packing density, d the distance separating the donor and acceptor sites, λ the reorganization energy and ∆G 0 the standard free energy of the reaction (energies are in eV).…”

Section: Discussionmentioning

confidence: 99%

Inter‐ and Intramolecular Electron Transfer in Modified Azurin Dimers

et al. 2007

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A dimer of N42C azurin (P. aeruginosa), formed by intermolecular disulfide bond formation between the introduced surface‐exposed cysteine residues, was previously shown to exhibit low rates of intramolecular electron self‐exchange. The work presented here aims to render the construct sensitive to pH by the introduction of an additional surface mutation (M64E). The structural and mechanistic effects of ionisable residues in the hydrophobic patch were analysed as a function of pH. A crystal structure of the dimer at pH = 3.1, solved to 2.3 Å resolution, displays an orientation distinct from other known azurin complexes. The dimer exhibits slow intramolecular self‐exchange at pH* = 4.5 (keseintra ≈ 25 s–1), in line with the Cu–Cu distance of 20.5 Å observed in the crystal structure of the dimer. The intermolecular electron self‐exchange rate constant amounts to kinter = (1.8 ± 0.1) ×104 M–1 s–1. Thus, at protein concentrations less than 1 mm, the intramolecular process dominates the electron self‐exchange. A change from low to high pH results in a slowing down of the electron‐exchange processes. A partitioning between intra‐ and intermolecular exchange proved impossible at low pH due to the limited precision of the experimental data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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“…6 and 12. A protein is then a poor conductor however but it is sufficient to allow tunnelling electron transfer at rates greater than 10 4 /s with gaps between sites of about 10 Å [54][55][56][57][58]. Now good doped semiconductors can have similar transfer rates at 100 Å distance while metals have no distance constraint, Fig.…”

Section: Electron Transfer In Conducting Solids: a Comparison With Enmentioning

confidence: 97%

“…The figure is modified from Messerschmidt et al [9]. by three different groups who refer to two different views as to the mechanism [54][55][56][57][58]. Using Marcus and general tunnelling theory in solid matrices we can view electron conduction in a further different manner from either, while making comparisons with other bulk matrices, see next section.…”

Section: Non-adjacent Sitesmentioning

confidence: 98%

A comparison of types of catalyst: The quality of metallo-enzymes

Williams

2008

Journal of Inorganic Biochemistry

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Biological electron tunneling through native protein media

Cited by 58 publications

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An approach to long-range electron transfer mechanisms in metalloproteins: In situ scanning tunneling microscopy with submolecular resolution

An approach to long-range electron transfer mechanisms in metalloproteins: In situ scanning tunneling microscopy with submolecular resolution

Inter‐ and Intramolecular Electron Transfer in Modified Azurin Dimers

A comparison of types of catalyst: The quality of metallo-enzymes

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