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Nanosecond Photoreduction of Cytochrome P450cam by Channel-Specific Ru-diimine Electron Tunneling Wires

Dunn, Alexander R. and Dmochowski, Ivan J. and Winkler, Jay R. and Gray, Harry B. (2003) Nanosecond Photoreduction of Cytochrome P450cam by Channel-Specific Ru-diimine Electron Tunneling Wires. Journal of the American Chemical Society, 125 (41). pp. 12450-12456. ISSN 0002-7863. doi:10.1021/ja0294111.

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We report the synthesis and characterization of Ru-diimine complexes designed to bind to cytochrome P450cam (CYP101). The sensitizer core has the structure [Ru(L_2)L‘]^(2+), where L‘ is a perfluorinated biphenyl bridge (F_8bp) connecting 4,4‘-dimethylbipyridine to an enzyme substrate (adamantane, F_8bp-Ad), a heme ligand (imidazole, F_8bp-Im), or F (F_9bp). The electron-transfer (ET) driving force (−ΔG°) is varied by replacing the ancillary 2,2‘-bipyridine ligands with 4,4‘,5,5‘-tetramethylbipyridine (tmRu). The four complexes all bind P450cam tightly:  Ru−F_8bp-Ad (1, K_d = 0.077 μM); Ru−F_8bp-Im (2, K_d = 3.7 μM); tmRu−F_9bp (3, K_d = 2.1 μM); and tmRu−F_8bp-Im (4, Kd = 0.48 μM). Binding is predominantly driven by hydrophobic interactions between the Ru-diimine wires and the substrate access channel. With Ru−F_8bp wires, redox reactions can be triggered on the nanosecond time scale. Ru-wire 2, which ligates the heme iron, shows a small amount of transient heme photoreduction (ca. 30%), whereas the transient photoreduction yield for 4 is 76%. Forward ET with 4 occurs in roughly 40 ns (k_f = 2.8 × 10^7 s^(-1)), and back ET (Fe^(II) → Ru^(III), k_b ≈ 1.7 × 10^8 s^(-1)) is near the coupling-limited rate (k_(max)). Direct photoreduction was not observed for 1 or 3. The large variation in ET rates among the Ru-diimine:P450 conjugates strongly supports a through-bond model of Ru−heme electronic coupling.

Item Type:Article
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URLURL TypeDescription Information
Dunn, Alexander R.0000-0001-6096-4600
Winkler, Jay R.0000-0002-4453-9716
Gray, Harry B.0000-0002-7937-7876
Additional Information:© 2003 American Chemical Society. Received 19 November 2002. Published online 23 September 2003. Published in print 1 October 2003. This work was supported by the Fannie and John Hertz Foundation (A.R.D.), the National Institutes of Health predoctoral program (I.J.D.), NSF CHE-0111416, and NIH DK19038.
Funding AgencyGrant Number
Fannie and John Hertz FoundationUNSPECIFIED
Issue or Number:41
Record Number:CaltechAUTHORS:20170516-065837544
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Official Citation:Nanosecond Photoreduction of Cytochrome P450cam by Channel-Specific Ru-diimine Electron Tunneling Wires Alexander R. Dunn, Ivan J. Dmochowski, Jay R. Winkler, and Harry B. Gray Journal of the American Chemical Society 2003 125 (41), 12450-12456 DOI: 10.1021/ja0294111
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77478
Deposited By: Ruth Sustaita
Deposited On:16 May 2017 16:40
Last Modified:15 Nov 2021 17:31

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