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Electron Tunneling in Single Crystals of Pseudomonas aeruginosa Azurins

Crane, Brian R. and Di Bilio, Angel J. and Winkler, Jay R. and Gray, Harry B. (2001) Electron Tunneling in Single Crystals of Pseudomonas aeruginosa Azurins. Journal of the American Chemical Society, 123 (47). pp. 11623-11631. ISSN 0002-7863. doi:10.1021/ja0115870.

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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 ∼17 Å) 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) × 10^6 s^(-1) (298 K), 1.8(8) × 10^6 s^(-1) (140 K), [Ru(bpy)_2(im)^(3+)-]; 3.0(15) × 10^6 s^(-1) (298 K), [Ru(tpy)(bpy)^(3+)-]; 3.0(15) × 10^6 s^(-1) (298 K), [Ru(tpy)(phen)^(3+)-]; 9.0(50) × 10^2 s^(-1) (298 K), [Os(bpy)2(im)^(3+)-]; 4.4(20) × 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 Å) and reduced (1.4 Å) 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 Å 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Winkler, Jay R.0000-0002-4453-9716
Gray, Harry B.0000-0002-7937-7876
Additional Information:© 2001 American Chemical Society. Received 28 June 2001. Published online 1 November 2001. Published in print 1 November 2001. We thank Mike Machczynski for experimental assistance, Doug Rees and Akif Tezcan for helpful discussions, and SSRL for access to data collection facilities. This research was supported by NIH (DK19038), the Helen Hay Whitney Foundation (fellowship to B.R.C.), and the Arnold and Mabel Beckman Foundation.
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Helen Hay Whitney FoundationUNSPECIFIED
Arnold and Mabel Beckman FoundationUNSPECIFIED
Issue or Number:47
Record Number:CaltechAUTHORS:20170515-150316333
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Official Citation:Electron Tunneling in Single Crystals of Pseudomonas aeruginosa Azurins Brian R. Crane, Angel J. Di Bilio, Jay R. Winkler, and Harry B. Gray Journal of the American Chemical Society 2001 123 (47), 11623-11631 DOI: 10.1021/ja0115870
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77466
Deposited By: Ruth Sustaita
Deposited On:16 May 2017 03:18
Last Modified:15 Nov 2021 17:31

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