Impact of self‐assembly composition on the alternate interfacial electron transfer for electrostatically immobilized cytochrome <i>c</i>

Dolidze, Tina D.; Rondinini, Sandra; Vertova, Alberto; Khoshtariya, Dimitri E.

doi:10.1002/bip.20789

Cited by 32 publications

(45 citation statements)

References 40 publications

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“…Previous studies that exploited SAM-coated electrodes revealed two kinds of phenomenological behavior (17)(18)(19)(20)(21)(22)(24)(25)(26)(27)(28)(29)(30)(31). For the case of thicker SAMs (long-range ET), these studies showed an exponential decay of k et with the SAM thickness (that is a part of the ET distance, R e ); in accordance with the nonadiabatic ET (tunneling) theory (1, 3, 17-22, 24-32, 46-50):…”

supporting

confidence: 74%

“…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)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(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.…”

mentioning

confidence: 99%

“…1 Å −1 for alkanethiol SAMs (17)(18)(19)(20)(21)(22)(24)(25)(26)(27)(28)(29)(30)(31)(32). Because of this well-recognized signature, a common consensus exists for the nonadiabatic nature of longrange ET through alkanethiol or other insulating SAMs, independent of the type of redox probe and its interaction mode with the SAM (1, 3, 17-22, 24-32, 46-50).…”

mentioning

confidence: 99%

“…where η is the zero-frequency, bulk shear viscosity, and δ is an "empirical" (27)(28)(29)56), which is the biological counterpart of the solvent-controlled (apparent adiabatic) mechanism. The same experimental signature has been proposed for the "conformational-gating" mechanism, which arises from an extra barrier-crossing event [e.g., (macro)molecular intra-or intermolecular rearrangement] that is not intrinsically coupled with ET but may be rate limiting.…”

mentioning

confidence: 99%

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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.

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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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supporting

confidence: 74%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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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.

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126

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“…two orders of magnitude less than those achieved at similarly modified planar gold electrodes. 54 The lower rate constants may arise from changes in the composition of the SAM, which have been observed with FcHxSH. Such changes can significantly change the faradaic reponse of the protein.…”

Section: Voltammetric Characterization Of Cyt C Immobilized On Planarmentioning

confidence: 98%

Characterization of Nanoporous Gold Electrodes for Bioelectrochemical Applications

Scanlon¹,

Salaj-Kośla²,

Belochapkine³

et al. 2011

Langmuir

101

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ABSTRACT. The high surface areas of nanostructured electrodes can provide for significantly enhanced surface loadings of electroactive materials. The fabrication and characterisation of nanoporous gold (np-Au) substrates as electrodes for bioelectrochemical applications is described.Robust np-Au electrodes were prepared by sputtering a gold-silver alloy onto a glass support and subsequent de-alloying of the silver component. Alloy layers were prepared with either a uniform or non-uniform distribution of silver and, post de-alloying, showed clear differences in morphology on characterisation with scanning electron microscopy. Redox reactions under kinetic control, in particular measurement of the charge required to strip a gold oxide layer, provided the most accurate measurements of the total electrochemically addressable electrode surface area, A real .Values of A real up to 28 times that of the geometric electrode surface area, A geo , were obtained. For diffusion controlled reactions overlapping diffusion zones between adjacent nanopores established limiting semi-infinite linear diffusion fields where the maximum current density was dependent on A geo . The importance of measuring the surface area available for the immobilisation was determined 2 using the redox protein, cyt c. The area accessible to modification by a biological macromolecule, A macro , such as cyt c was reduced by up to 40 % compared to A real , demonstrating that the confines of some nanopores were inaccessible to large macromolecules due to steric hindrances. Preliminary studies on the preparation of np-Au electrodes modified with osmium redox polymer hydrogels and Myrothecium verrucaria bilirubin oxidase (MvBOD) as a biocathode were performed; current densities of 500 A cm -2 were obtained in unstirred solutions.

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Diverse role of conformational dynamics in carboxypeptidase A‐driven peptide and ester hydrolyses: Disclosing the “Perfect Induced Fit” and “Protein Local Unfolding” pathways by altering protein stability

et al. 2011

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Catalytic mechanisms of carboxypeptidase A (CPA) are well known for their diversity and the relative inaccessibility for a decisive comprehension. Recent encouraging attempts through modern computational techniques promoted new challenges for the complementary experimental endeavors. In this work, we have applied the stopped-flow technique and the method of reaction progress curve fitting to extract kinetic parameters for the CPA-catalyzed hydrolyses of smaller (typical) peptide and ester substrates, known for their strong activating/inhibiting impact, thus to which the traditional method of "initial rates" is not applicable. Our approach that innately implies the overall constancy of the affecter (substrate plus "active" product) concentration, made it possible to rigorously determine the physically meaningful "effective" values for the catalytic and Michaelis constants under diverse experimental conditions including variable temperature and urea or trimethylamine N-oxide concentrations. Analysis of the obtained results allowed for: (i) the further substantiation of diverse mechanistic patterns for archetypal specific peptide and ester substrates, (ii) testing and disclosure of intrinsic links between the stabilizing/destabilizing and activating/inhibiting effects for the important model enzyme, CPA, and (iii) tentative explanation of a distinct activating/inhibiting impact of these substrates through the strong specific interaction of their benzyl (Bz) moiety with the substrate binding S(3) subsite of CPA. We have demonstrated that stabilization of CPA either through the interaction with an extra Bz moiety (belonging to another substrate or to the product) leads to the increase of its catalytic power with respect to the specific peptide substrate and to its decrease with respect to the counterpart ester substrate. We conjecture that the catalytic mechanisms operating in these two cases include: (a) the "promoted water" mechanism for the peptide substrate that, seemingly, provides the almost "perfect induced fit" (low-barrier conformational adaptation), and (b) presumably, the "anhydride intermediate" mechanism for the ester substrate that, anyway, requires substantial conformational rearrangement (in fact, "partial or local unfolding") of the protein environment in the course of the rate-determining step.

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Impact of self‐assembly composition on the alternate interfacial electron transfer for electrostatically immobilized cytochrome c

Cited by 32 publications

References 40 publications

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

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

Characterization of Nanoporous Gold Electrodes for Bioelectrochemical Applications

Diverse role of conformational dynamics in carboxypeptidase A‐driven peptide and ester hydrolyses: Disclosing the “Perfect Induced Fit” and “Protein Local Unfolding” pathways by altering protein stability

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