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Electron Tunneling in Engineered Proteins

Mines, Gary A. and Ramirez, Benjamin E. and Gray, Harry B. and Winkler, Jay R. (1998) Electron Tunneling in Engineered Proteins. In: Photochemistry and Radiation Chemistry. Advances in Chemistry. No.254. American Chemical Society , Washington, DC, pp. 51-63. ISBN 9780841234994.

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Semiclassical theory predicts that the rates of electron transfer (ET) reactions depend on the reaction driving force (-ΔG°), a nuclear reorganization parameter (λ), and the electronic-coupling strength (H_(AB)) between reactants and products at the transition state. ET rates reach their maximum values (k°_(ET)) when the nuclear factor is optimized (-ΔG° = λ); these k°_(ET) values are limited only by the strength (H^2_(AB)) of the electronic interaction between the donor (D) and acceptor (A). The dependence of the rates of Ru(His33)cytochrome c ET reactions on -ΔG° (0.59-1.4 eV) accords closely with semiclassical predictions. The anomalously high rates of highly exergonic (-ΔG° ≥ 1.4 eV) ET reactions suggest initial formation of an electronically excited ferroheme in these cases. Coupling-limited Cu^+ to Ru^(3+) and Fe^(2+) to Ru^(3+) ET rates for several Ru-modified proteins are in good agreement with the predictions of a tunneling-pathway model. In azurin, a blue copper protein, the distant D-A pairs are relatively well coupled (k°_(ET) decreases exponentially with Cu-Ru distance; the decay constant is 1.1 Å^(-1)). In contrast to the extended peptides found in azurin and other β-sheet proteins, helical structures have torturous covalent pathways owing to the curvature of the peptide backbone. The decay constants estimated from ET rates for D-A pairs separated by long sections of α helix in myoglobin and the photosynthetic reaction center are between 1.25 and 1.6 Å^(-1).

Item Type:Book Section
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URLURL TypeDescription
Gray, Harry B.0000-0002-7937-7876
Winkler, Jay R.0000-0002-4453-9716
Additional Information:© 1998 American Chemical Society. Published in print 17 April 1998. Our work on electron transfer in proteins is supported by the National Science Foundation, the National Institutes of Health, and the Arnold and Mabel Beckman Foundation.
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Arnold and Mabel Beckman FoundationUNSPECIFIED
Series Name:Advances in Chemistry
Issue or Number:254
Record Number:CaltechAUTHORS:20180406-080327489
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Official Citation:Electron Tunneling in Engineered Proteins Gary A. Mines, Benjamin E. Ramirez, Harry B. Gray, and Jay R. Winkler Photochemistry and Radiation Chemistry. April 17, 1998, 51-63 DOI:10.1021/ba-1998-0254.ch004
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85675
Deposited By: Ruth Sustaita
Deposited On:06 Apr 2018 16:14
Last Modified:15 Nov 2021 20:31

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