Electron transfer in blue copper proteins

Farver, Ole; Pecht, Israel

doi:10.1016/j.ccr.2010.08.005

Cited by 64 publications

(59 citation statements)

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“…Here we report the results of studying intramolecular ET from a disulfide radical anion, produced by pulse radiolysis, to the Cu(II) center in several of these Az mutants. The results presented here suggest that the reactions proceed with a lower reorganization free energy compared with wild-type Az and other mutants studied so far (18). Furthermore, the ET rates in these mutants fit the curve predicted by the Marcus theory, and at the highest driving force of >1.0 eV, a decline in rate suggests entry into the Marcus inverted region.…”

Section: Marcus Inverted Regionsupporting

confidence: 55%

“…Despite many years of work, few efforts have succeeded in designing protein ET sites having reorganization free energies lower than those observed for the native ones. For example, numerous mutations proximal to the type 1 (T1) blue copper site have been introduced into azurin (Az) (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), a bacterial electron-mediating protein, but those that have lowered this barrier have not been reported yet.…”

Section: Marcus Inverted Regionmentioning

confidence: 99%

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Designed azurins show lower reorganization free energies for intraprotein electron transfer

Farver

Marshall

Wherland

et al. 2013

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

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Low reorganization free energies are necessary for fast electron transfer (ET) reactions. Hence, rational design of redox proteins with lower reorganization free energies has been a long-standing challenge, promising to yield a deeper understanding of the underlying principles of ET reactivity and to enable potential applications in different energy conversion systems. Herein we report studies of the intramolecular ET from pulse radiolytically produced disulfide radicals to Cu(II) in rationally designed azurin mutants. In these mutants, the copper coordination sphere has been fine-tuned to span a wide range of reduction potentials while leaving the metal binding site effectively undisrupted. We find that the reorganization free energies of ET within the mutants are indeed lower than that of WT azurin, increasing the intramolecular ET rate constants almost 10-fold: changes that are correlated with increased flexibility of their copper sites. Moreover, the lower reorganization free energy results in the ET rate constants reaching a maximum value at higher driving forces, as predicted by the Marcus theory.cupredoxin | Type 1 copper | blue copper | reorganization energy | Marcus inverted region E lectron transfer (ET) through proteins is central to biological energy conversion processes, from photosynthesis to respiration (1). ET rates between redox centers are tightly controlled and tuned in biological systems for efficiency and to avoid formation of deleterious products (2-5). An important parameter determining the ET rate is the reorganization free energy of the redox sites (6-8), which for biochemical ET reactions has evolved to low values, usually providing high rate constants. Despite many years of work, few efforts have succeeded in designing protein ET sites having reorganization free energies lower than those observed for the native ones. For example, numerous mutations proximal to the type 1 (T1) blue copper site have been introduced into azurin (Az) (9-19), a bacterial electron-mediating protein, but those that have lowered this barrier have not been reported yet.Prominent among the theories developed to rationalize the control of ET reaction rates (20-22) is that of R. A. Marcus (23). A particularly intriguing element of this theory predicts that the ET rate reaches its maximum when the driving force of the reaction equals the reorganization free energy, after which an even higher driving force decreases ET rate, reaching the "Marcus inverted region." It has been proposed that the dramatic difference in rates between some of the forward and backward ET reactions in the photosynthetic reaction center is a result of the latter being in the inverted region, which is reached because of exceptionally low reorganization free energies of the relevant ET sites (24).In the present study, we aim at examining how the major changes in modifying the redox potential of the type 1 copper site in Az achieved by Marshall et al. (25) affect its ET reactivity. A major obstacle in rationally fine-tuning the properties of t...

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Section: Marcus Inverted Regionsupporting

confidence: 55%

Section: Marcus Inverted Regionmentioning

confidence: 99%

Designed azurins show lower reorganization free energies for intraprotein electron transfer

Farver

Marshall

Wherland

et al. 2013

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

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“…[40] Copper-disulfide interactions are of significance in the context of redox or electron transfer processes in biological systems. [15,41,42] The disulfide → thiolate interconversion between RSSR and 2RS -on a distinct dicopper unit has been established for model systems [43] and disulfides have been used recently as an oxidant for Cu(I). [15] Complex 5c with a markedly elongated S−S bond coordinated to two copper centers may be considered as a model for the intermediates involved in oxidative-additions of disulfides to Cu(I).…”

Section: Resultsmentioning

confidence: 99%

Bond Stretching and Redox Behavior in Coinage Metal Complexes of the Dichalcogenide Dianions [(SPh₂P)₂CEEC(PPh₂S)₂]²⁻ (E=S, Se): Diradical Character of the Dinuclear Copper(I) Complex (E=S)

Konu

Chivers

Tuononen

2011

Chemistry A European J

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The metathetical reactions of a) [Li(tmeda)]2[(S)C(PPh2S)2] (Li2⋅3 c) with CuCl2 and b) [Li(tmeda)]2[(SPh2P)2CSSC(PPh2S)2] (Li2⋅4 c) with two equivalents of CuCl both afford the binuclear CuI complex {Cu2[(SPh2P)2CSSC(PPh2S)2]} (5 c). The elongated (C)SS(C) bond (ca. 2.54 and 2.72 Å) of the dianionic ligand observed in the solid‐state structure of 5 c indicate the presence of diradical character as supported by theoretical analyses. The treatment of [Li(tmeda)]2[(SPh2P)2CSeSeC(PPh2S)2] (Li2⋅4 b) and Li2⋅4 c with AgOSO2CF3 produce the analogous AgI derivatives, {Ag2[(SPh2P)2CEEC(PPh2S)2]} (6 b, E=Se; 6 c, E=S), respectively. The diselenide complex 6 b exhibits notably weaker AgSe(C) bonds than the corresponding contacts in the CuI congeners, and the 31P NMR data suggest a possible isomerization in solution. In contrast to the metathesis observed for CuI and AgI reagents, the reactions of Li2⋅4 b and Li2⋅4 c with Au(CO)Cl involve a redox process in which the dimeric dichalcogenide ligands are reduced to the corresponding monomeric dianions, [(E)C(PPh2S)2]2− (3 b, E=Se; 3 c, E=S), and one of the gold centers is oxidized to generate the mixed‐valent AuI/AuIII complexes, {Au[(E)C(PPh2S)2]}2 (7 b, E=Se; 7 c, E=S), with relatively strong aurophilic AuI⋅⋅⋅AuIII interactions. The new compounds 5 c, 6 b,c and 7 b,c are characterized in solution by NMR spectroscopy and in the solid state by X‐ray crystallography (5 c, 6 b, 7 b and 7 c) and by Raman spectroscopy (5 c and 6 c). The UV‐visible spectra of coinage metal complexes of the type 5, 6 and 7 are discussed in the light of results from theoretical analyses using time‐dependent density functional theory.

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“…Long-distance electron transfer (ET) plays an essential role in biological energy conversion [1][2][3][4][5]. Representative are those in photosynthetic reaction centers in which photon energy is converted to electrochemical energy via series of ETs through redox centers embedded in transmembrane protein.…”

Section: Introductionmentioning

confidence: 99%

FMO3-LCMO study of electron transfer coupling matrix element and pathway: Application to hole transfer between two tryptophans through cis- and trans-polyproline-linker systems

Kitoh-Nishioka

Ando

2016

The Journal of Chemical Physics

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The linear-combination of fragment molecular orbitals with three-body correction (FMO3-LCMO) is examined for electron transfer (ET) coupling matrix elements and ET pathway analysis, with application to hole transfer between two triptophanes bridged by cis-and trans-polyproline linker conformations. A projection to the minimal-valence-plus-core FMO space was found to give sufficient accuracy with significant reduction of computational cost while avoiding the problem of linear dependence of FMOs stemming from involvement of bond detached atoms.

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Electron transfer in blue copper proteins

Cited by 64 publications

References 123 publications

Designed azurins show lower reorganization free energies for intraprotein electron transfer

Designed azurins show lower reorganization free energies for intraprotein electron transfer

Bond Stretching and Redox Behavior in Coinage Metal Complexes of the Dichalcogenide Dianions [(SPh₂P)₂CEEC(PPh₂S)₂]²⁻ (E=S, Se): Diradical Character of the Dinuclear Copper(I) Complex (E=S)

FMO3-LCMO study of electron transfer coupling matrix element and pathway: Application to hole transfer between two tryptophans through cis- and trans-polyproline-linker systems

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Electron transfer in blue copper proteins

Cited by 64 publications

References 123 publications

Designed azurins show lower reorganization free energies for intraprotein electron transfer

Designed azurins show lower reorganization free energies for intraprotein electron transfer

Bond Stretching and Redox Behavior in Coinage Metal Complexes of the Dichalcogenide Dianions [(SPh2P)2CEEC(PPh2S)2]2− (E=S, Se): Diradical Character of the Dinuclear Copper(I) Complex (E=S)

FMO3-LCMO study of electron transfer coupling matrix element and pathway: Application to hole transfer between two tryptophans through cis- and trans-polyproline-linker systems

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Bond Stretching and Redox Behavior in Coinage Metal Complexes of the Dichalcogenide Dianions [(SPh₂P)₂CEEC(PPh₂S)₂]²⁻ (E=S, Se): Diradical Character of the Dinuclear Copper(I) Complex (E=S)