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Electron-Transfer Chemistry of Ru−Linker−(Heme)-Modified Myoglobin: Rapid Intraprotein Reduction of a Photogenerated Porphyrin Cation Radical

Immoos, Chad E. and Di Bilio, Angel J. and Cohen, Michael S. and Van der Veer, Wytze and Gray, Harry B. and Farmer, Patrick J. (2004) Electron-Transfer Chemistry of Ru−Linker−(Heme)-Modified Myoglobin: Rapid Intraprotein Reduction of a Photogenerated Porphyrin Cation Radical. Inorganic Chemistry, 43 (12). pp. 3593-3596. ISSN 0020-1669. http://resolver.caltech.edu/CaltechAUTHORS:20170425-071456736

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Abstract

We report the synthesis and characterization of RuC7, a complex in which a heme is covalently attached to a [Ru(bpy)_3]^(2+) complex through a −(CH_2)_7− linker. Insertion of RuC7 into horse heart apomyoglobin gives RuC7Mb, a Ru(heme)−protein conjugate in which [Ru(bpy)_3]^(2+) emission is highly quenched. The rate of photoinduced electron transfer (ET) from the resting (Ru^(2+)/Fe^(3+)) to the transient (Ru^(3+)/Fe^(2+)) state of RuC7Mb is >10^8 s^(-1); the back ET rate (to regenerate Ru^(2+)/Fe^(3+)) is 1.4 × 10^7 s^(-1). Irreversible oxidative quenching by [Co(NH_3)_5Cl]^(2+) generates Ru^(3+)/Fe^(3+):  the Ru^(3+) complex then oxidizes the porphyrin to a cation radical (P^(•+)); in a subsequent step, P^(•+) oxidizes both Fe^(3+) (to give Fe^(IV)═O) and an amino acid residue. The rate of intramolecular reduction of P^(•+) is 9.8 × 10^3 s^(-1); the rate of ferryl formation is 2.9 × 10^3 s^(-1). Strong EPR signals attributable to tyrosine and tryptophan radicals were recorded after RuC7MbM^(3+) (M = Fe, Mn) was flash-quenched/frozen.


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URLURL TypeDescription
http://dx.doi.org/10.1021/ic049741hDOIArticle
http://pubs.acs.org/doi/full/10.1021/ic049741hPublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/ic049741hPublisherSupporting Information
Additional Information:© 2004 American Chemical Society. Received 28 February 2004. Published online 29 April 2004. Published in print 1 June 2004. We thank Kevin Heinrich, David Khandabi, and Greg Quishair for assistance with the synthesis of RuC7. C.E.I. thanks the UC TSR & TP for a graduate fellowship. M.S.C. thanks the Arnold and Mabel Beckman Undergraduate Scholarship Fund for support. This work was supported by the NSF (P.J.F., Grant CHE-0100774), UROP funding from UCI, and the NIH (H.B.G., Grant DK19038).
Funders:
Funding AgencyGrant Number
Arnold and Mabel Beckman FoundationUNSPECIFIED
NSFCHE-0100774
University of California, IrvineUNSPECIFIED
NIHDK19038
Record Number:CaltechAUTHORS:20170425-071456736
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170425-071456736
Official Citation:Electron-Transfer Chemistry of Ru−Linker−(Heme)-Modified Myoglobin:  Rapid Intraprotein Reduction of a Photogenerated Porphyrin Cation Radical Chad E. Immoos, Angel J. Di Bilio, Michael S. Cohen, Wytze Van der Veer, Harry B. Gray, and Patrick J. Farmer Inorganic Chemistry 2004 43 (12), 3593-3596 DOI: 10.1021/ic049741h
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76894
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:25 Apr 2017 15:02
Last Modified:25 Apr 2017 15:02

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