Electron Transfer—from Isolated Molecules to Biomolecules

Bixon, M.; Jortner, Joshua

doi:10.1002/9780470141656.ch3

Cited by 474 publications

(359 citation statements)

References 773 publications

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“…The latter is dependent on the dielectric and polarisable properties of the medium, [24][25][26][27][28][29] the former is the energy associated with the structural changes of the reactants on progression to product geometry (and vice versa). [24][25][26]30] The contribution to λ from λ i can be significant and dominates inner sphere charge transfer processes (those CT processes where there are no solvent molecules intervening to prevent molecular contact between reactants). [23] In general, λ i increases with increasing localisation of charge whether dealing with monomeric or oligomeric materials.…”

Section: Introductionmentioning

confidence: 99%

“…Self-exchange charge transfer reactions may be considered [23] to be the primary mediators of charge flow in organic conducting polymers and amorphous thin films. At room temperature in such environments these reactions are usually considered to involve a series of thermally activated electron and/or hole hops between adjacent charged radical ions and neutral parent species; Rate constants, k CT for both hole and electron transfer self-exchange processes can be expressed using the semi-classical form of the Marcus equation (Equation 1): [24][25][26] √ [ ] where k CT is the rate constant for electron transfer, k B and T are the Boltzmann constants and temperature respectively, λ is the reorganisation energy and V is the electronic coupling factor, sometimes referred to as the charge transfer integral, t. It can be seen that for an iso-energetic charge transfer process, k CT depends only on V and λ. In turn, λ is divided into contributions from two components; inner and outer sphere reorganisation energies, λ i and λ o respectively.…”

Section: Introductionmentioning

confidence: 99%

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Torsional angle dependence and switching of inner sphere reorganisation energies for electron and hole transfer processes involving phenyl substituted diketopyrrolopyrroles; a density functional study

2015

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angle dependence and switching of inner sphere reorganisation energies for electron and hole transfer processes involving phenyl substituted diketopyrrolopyrroles; a density functional study ', Dyes and Pigments, Vol. 113, pp. 609-617, February 2015 AbstractDetermination of inner sphere reorganisation energies is important in the development of organic charge mediating materials and electron transfer reactions. In this study, hole and electron inner sphere reorganisation energies, λ h and λ e respectively, have been computed for the first time for a series of structurally related diketopyrrolopyrrole (DPP) molecular motifs. Inner sphere reorganisation energies for self-exchange electron transfer reactions are calculated as being lower than those associated hole transfer processes in model planar phenyl and thiophenyl substituted DPP systems. It is found that λ e < λ h for all planar ring / DPP core structures examined. The effect on λ h/e of nonplanarity between phenyl substituents and DPP core is explored in detail. The relative ordering of λ h and λ e is dependent upon the torsional angle of phenyl rings and reverses at twist angles of greater than 60⁰ such that λ e > λ h .

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Torsional angle dependence and switching of inner sphere reorganisation energies for electron and hole transfer processes involving phenyl substituted diketopyrrolopyrroles; a density functional study

2015

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“…T he intrinsic electron transfer (ET) mechanisms of even small and otherwise well-characterized proteins such as cytochrome c or azurin (Az) are difficult to identify conclusively because of the proteins' complexity, i.e., inhomogeneous structural and dynamic properties (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). The use of bioelectrochemical tunneling junctions, such as self-assembled monolayer (SAM) films of variable composition and thickness on metal electrodes, with redox proteins immobilized at the solution interface (or freely diffusing to the SAM terminal groups) have been shown to provide an assembly with well-defined and variable control parameters.…”

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confidence: 99%

Fundamental signatures of short- and long-range electron transfer for the blue copper protein azurin at Au/SAM junctions

Khoshtariya

Dolidze

Shushanyan

et al. 2010

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

126

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The blue copper protein from Pseudomonas aeruginosa, azurin, immobilized at gold electrodes through hydrophobic interaction with alkanethiol self-assembled monolayers (SAMs) of the general type [−S − ðCH 2 Þ n − CH 3 ] (n ¼ 4, 10, and 15) was employed to gain detailed insight into the physical mechanisms of short-and long-range biomolecular electron transfer (ET). Fast scan cyclic voltammetry and a Marcus equation analysis were used to determine unimolecular standard rate constants and reorganization free energies for variable n, temperature (2-55°C), and pressure (5-150 MPa) conditions. A novel global fitting procedure was found to account for the reduced ET rate constant over almost five orders of magnitude (covering different n, temperature, and pressure) and revealed that electron exchange is a direct ET process and not conformationally gated. All the ET data, addressing SAMs with thickness variable over ca. 12 Å, could be described by using a single reorganization energy (0.3 eV), however, the values for the enthalpies and volumes of activation were found to vary with n. These data and their comparison with theory show how to discriminate between the fundamental signatures of short-and long-range biomolecular ET that are theoretically anticipated for the adiabatic and nonadiabatic ET mechanisms, respectively. electron transfer mechanism | pressure | protein friction | reorganization | temperature T he intrinsic electron transfer (ET) mechanisms of even small and otherwise well-characterized proteins such as cytochrome c or azurin (Az) are difficult to identify conclusively because of the proteins' complexity, i.e., inhomogeneous structural and dynamic properties (1-14). The use of bioelectrochemical tunneling junctions, such as self-assembled monolayer (SAM) films of variable composition and thickness on metal electrodes, with redox proteins immobilized at the solution interface (or freely diffusing to the SAM terminal groups) have been shown to provide an assembly with well-defined and variable control parameters. As such, these assemblies are well suited for fundamental studies (15-32) and offer promise for versatile nanotechnology applications (32,33). On the basis of earlier fundamental efforts, this work studies ET between a Au electrode that is coated with a SAM alkanethiol film of variable thickness and a "model" biomolecular target, the blue copper protein, Az, from Pseudomonas aeruginosa that is immobilized through hydrophobic interactions onto the SAM. As a decisive development of the preceding work (19,20,25,26), we offer unique kinetic data obtained through temperature-and pressure-variation and the mechanistic analysis through a unique global fitting procedure accounting for ET at different SAM thickness, temperature, and pressure conditions that provided the variation of the reduced ET rate constant over almost five orders of magnitude. Importantly, our previous work demonstrated that Au-deposited SAMs can withstand pressure-related stress within 5 to 150 MPa (27, 28, 34).The rate constant, k ...

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“…22 The former assumes that only the first two cumulants of q are significant for time-independent (stationary) lineshapes measured in the limit t → ∞. The corresponding absorption and emission lineshapes are given by Gaussian functions, 36 with their maxima separated by the Stokes shift ∆Ω =Ω g −Ω e ,…”

Section: Time-resolved Lineshapesmentioning

confidence: 99%

Non-Gaussian Lineshapes and Dynamics of Time-Resolved Linear and Nonlinear (Correlation) Spectra

Dinpajooh

Matyushov

2014

J. Phys. Chem. B

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Signatures of nonlinear and non-Gaussian dynamics in time-resolved linear and nonlinear (correlation) 2D spectra are analyzed in a model considering a linear plus quadratic dependence of the spectroscopic transition frequency on a Gaussian nuclear coordinate of the thermal bath (quadratic coupling). This new model is contrasted to the commonly assumed linear dependence of the transition frequency on the medium nuclear coordinates (linear coupling). The linear coupling model predicts equality between the Stokes shift and equilibrium correlation functions of the transition frequency and time-independent spectral width. Both predictions are often violated, and we are asking here the question of whether a nonlinear solvent response and/or non-Gaussian dynamics are required to explain these observations. We find that correlation functions of spectroscopic observables calculated in the quadratic coupling model depend on the chromophore's electronic state and the spectral width gains time dependence, all in violation of the predictions of the linear coupling models. Lineshape functions of 2D spectra are derived assuming Ornstein-Uhlenbeck dynamics of the bath nuclear modes. The model predicts asymmetry of 2D correlation plots and bending of the center line. The latter is often used to extract two-point correlation functions from 2D spectra. The dynamics of the transition frequency are non-Gaussian. However, the effect of non-Gaussian dynamics is limited to the third-order (skewness) time correlation function, without affecting the time correlation functions of higher order. The theory is tested against molecular dynamics simulations of a model polar-polarizable chromophore dissolved in a force field water.

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Electron Transfer—from Isolated Molecules to Biomolecules

Cited by 474 publications

References 773 publications

Torsional angle dependence and switching of inner sphere reorganisation energies for electron and hole transfer processes involving phenyl substituted diketopyrrolopyrroles; a density functional study

Torsional angle dependence and switching of inner sphere reorganisation energies for electron and hole transfer processes involving phenyl substituted diketopyrrolopyrroles; a density functional study

Fundamental signatures of short- and long-range electron transfer for the blue copper protein azurin at Au/SAM junctions

Non-Gaussian Lineshapes and Dynamics of Time-Resolved Linear and Nonlinear (Correlation) Spectra

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