Hartings, Matthew R. and Kurnikov, Igor V. and Dunn, Alexander R. and Winkler, Jay R. and Gray, Harry B. and Ratner, Mark A. (2010) Electron tunneling through sensitizer wires bound to proteins. Coordination Chemistry Reviews , 254 (3-4). pp. 248-253. ISSN 0010-8545 http://resolver.caltech.edu/CaltechAUTHORS:20100217-095253375
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We report a quantitative theoretical analysis of long-range electron transfer through sensitizer wires bound in the active-site channel of cytochrome P450cam. Each sensitizer wire consists of a substrate group with high binding affinity for the enzyme active site connected to a ruthenium-diimine through a bridging aliphatic or aromatic chain. Experiments have revealed a dramatic dependence of electron transfer rates on the chemical composition of both the bridging group and the substrate. Using combined molecular dynamics simulations and electronic coupling calculations, we show that electron tunneling through perfluorinated aromatic bridges is promoted by enhanced superexchange coupling through virtual reduced states. In contrast, electron flow through aliphatic bridges occurs by hole-mediated superexchange. We have found that a small number of wire conformations with strong donor–acceptor couplings can account for the observed electron tunneling rates for sensitizer wires terminated with either ethylbenzene or adamantane. In these instances, the rate is dependent not only on electronic coupling of the donor and acceptor but also on the nuclear motion of the sensitizer wire, necessitating the calculation of average rates over the course of a molecular dynamics simulation. These calculations along with related recent findings have made it possible to analyze the results of many other sensitizer-wire experiments that in turn point to new directions in our attempts to observe reactive intermediates in the catalytic cycles of P450 and other heme enzymes.
|Additional Information:||© 2009 Elsevier B.V. Received 23 June 2009; accepted 7 August 2009. Available online 15 August 2009. Inorganic Reaction Mechanisms - A Tribute to Ralph Pearson on the occasion of his 90th birthday. We thank David Beratan for helpful discussions. This work was supported by NIH (GM078792 to MRH and DK019038 to HBG and GM068461 to JRW) and NSF (CHE-0802907 to HBG and JRW). MR thanks the MURI program of the AFOSR and the Chemistry Division of the NSF for support. This paper is dedicated to Ralph Pearson—friend, mentor, colleague, scientist and honest broker.|
|Subject Keywords:||Cytochrome P450; Protein electron transfer; Conformational dynamics electron transfer; Bridge effects electron transfer|
|Official Citation:||Matthew R. Hartings, Igor V. Kurnikov, Alexander R. Dunn, Jay R. Winkler, Harry B. Gray, Mark A. Ratner, Electron tunneling through sensitizer wires bound to proteins, Coordination Chemistry Reviews, Volume 254, Issues 3-4, Inorganic Reaction Mechanisms - A Tribute to Ralph Pearson on the occasion of his 90th birthday, February 2010, Pages 248-253, ISSN 0010-8545, DOI: 10.1016/j.ccr.2009.08.008. (http://www.sciencedirect.com/science/article/B6TFW-4X0XFBY-4/2/2ebbf79dff58fdac7643edd7758e27ef)|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||19 Feb 2010 18:20|
|Last Modified:||26 Dec 2012 11:46|
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