Effects of driving force on the rates of intramolecular and bimolecular electron-transfer reactions

Gray, Harry B.; Winkler, Jay R.; Wiedenfeld, David

doi:10.1016/s0010-8545(00)00261-7

Cited by 11 publications

(8 citation statements)

References 30 publications

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“…The largest difference in ET rate constant between a crystal and solution is for the OsAz complex, where the reaction is roughly 5-fold slower in a crystal . The absence of an inverted effect for the Cu(I) → Re(I)* ET reaction is not unexpected, , as there are low-lying electronic excited states of Cu(II) that likely are formed as initial products. , …”

Section: Resultsmentioning

confidence: 87%

Electron Tunneling in Single Crystals ofPseudomonas aeruginosaAzurins

et al. 2001

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Rates of reduction of Os(III), Ru(III), and Re(I) by Cu(I) in His83-modified Pseudomonas aeruginosa azurins (M-Cu distance approximately 17 A) have been measured in single crystals, where protein conformation and surface solvation are precisely defined by high-resolution X-ray structure determinations: 1.7(8) x 10(6) s(-1) (298 K), 1.8(8) x 10(6) s(-1) (140 K), [Ru(bpy)2(im)(3+)-]; 3.0(15) x 10(6) s(-1) (298 K), [Ru(tpy)(bpy)(3+)-]; 3.0(15) x 10(6) s(-1) (298 K), [Ru(tpy)(phen)(3+)-]; 9.0(50) x 10(2) s(-1) (298 K), [Os(bpy)2(im)(3+)-]; 4.4(20) x 10(6) s(-1) (298 K), [Re(CO)3(phen)(+)] (bpy = 2,2'-bipyridine; im = imidazole; tpy = 2,2':6',2' '-terpyridine; phen = 1,10-phenanthroline). The time constants for electron tunneling in crystals are roughly the same as those measured in solution, indicating very similar protein structures in the two states. High-resolution structures of the oxidized (1.5 A) and reduced (1.4 A) states of Ru(II)(tpy)(phen)(His83)Az establish that very small changes in copper coordination accompany reduction but reveal a shorter axial interaction between copper and the Gly45 peptide carbonyl oxygen [2.6 A for Cu(II)] than had been recognized previously. Although Ru(bpy)2(im)(His83)Az is less solvated in the crystal, the reorganization energy for Cu(I) --> Ru(III) electron transfer falls in the range (0.6-0.8 eV) determined experimentally for the reaction in solution. Our work suggests that outer-sphere protein reorganization is the dominant activation component required for electron tunneling.

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Section: Resultsmentioning

confidence: 87%

Electron Tunneling in Single Crystals ofPseudomonas aeruginosaAzurins

et al. 2001

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“…As shown in Table , measurements of λ for blue copper proteins are similar to those of proteins and enzymes that display little reorganization of the cofactor upon redox changes. These observations suggest that redox proteins of Cu have evolved to constrain the environment about the redox cofactor . Specifically, numerous crystal structures show apo- and native-protein structures that are nearly similar.…”

Section: Reorganization Energies In Biological Electron Transfermentioning

confidence: 96%

“…Most ET reactions in biology occur over distances of 10−15 Å by tunneling mechanisms. ET analyzed in small proteins, in which a redox cofactor is appended at a specific position of known distance from a second redox cofactor and characterized structurally, has allowed determination of generic λ and β values. ,,, These model systems are unencumbered by conformational changes that often mask the redox reactions associated with more complex proteins. Also, minimal flexibility in varying the driving force of the reaction in these complex proteins to study ET makes determination of λ difficult.…”

Section: Summary: Et In Biological Systems and The Uniqueness Of Rnrsmentioning

confidence: 99%

“…These observations suggest that redox proteins of Cu have evolved to constrain the environment about the redox cofactor. 81 Specifically, numerous crystal structures show apo-and native-protein structures that are nearly similar. A heavily hydrogen-bonded network in the folded structure of copper proteins excludes water and strictly controls the positions of the ligands to copper, especially the axial ligand.…”

Section: Reorganization Energies In Biological Electron Transfermentioning

confidence: 99%

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Radical Initiation in the Class I Ribonucleotide Reductase: Long-Range Proton-Coupled Electron Transfer?

et al. 2003

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“…l i is directly related to the coordinate changes Dq from D*A to D + A À . [8][9][10][11][12][13][14][15] Detailed kinetic information for photochemical and photophysical reactions has become readily available from timeresolved optical spectroscopic studies. [7] The photoexcitation of the molecule also induces the spin-state transition via the excited states on which the structural changes take place, because of the rearrangement of electrons among different orbitals ( Figure 2).…”

Section: Importance Of Excited State Structural Informationmentioning

confidence: 99%

Taking Snapshots of Photoexcited Molecules in Disordered Media by Using Pulsed Synchrotron X‐rays

Chen

2004

Angew Chem Int Ed

112

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Photoexcited molecules are quintessential reactants in photochemistry. Structures of these photoexcited molecules in disordered media in which a majority of photochemical reactions take place remained elusive for decades owing to a lack of suitable X-ray sources, despite their importance in understanding fundamental aspects in photochemistry. As new pulsed X-ray sources become available, short-lived excited-state molecular structures in disordered media can now be captured by using laser-pulse pump, X-ray pulse-probe techniques of third-generation synchrotron sources with time resolutions of 30-100 ps, as demonstrated by examples in this review. These studies provide unprecedented information on structural origins of molecular properties in the excited states. By using other ultrafast X-ray facilities that will be completed in the near future, time-resolution for the excited-state structure measurements should reach the femtosecond time scales, which will make "molecular movies" of bond breaking or formation, and vibrational relaxation, a reality.

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Effects of driving force on the rates of intramolecular and bimolecular electron-transfer reactions

Cited by 11 publications

References 30 publications

Electron Tunneling in Single Crystals ofPseudomonas aeruginosaAzurins

Electron Tunneling in Single Crystals ofPseudomonas aeruginosaAzurins

Radical Initiation in the Class I Ribonucleotide Reductase: Long-Range Proton-Coupled Electron Transfer?

Taking Snapshots of Photoexcited Molecules in Disordered Media by Using Pulsed Synchrotron X‐rays

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