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Principles of Bioinorganic Chemistry - 2004

Principles of Bioinorganic Chemistry - 2004. Long-Distance Electron Transfer in Proteins. Three ways to measure :. 1. Self-exchange 2. Artificial donor-acceptor pairs 3. Study of natural protein redox pairs. Red Az. + Ox Az. Ox Az. + Red Az.

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Principles of Bioinorganic Chemistry - 2004

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  1. Principles of Bioinorganic Chemistry - 2004

  2. Long-Distance Electron Transfer in Proteins Three ways to measure: 1. Self-exchange 2. Artificial donor-acceptor pairs 3. Study of natural protein redox pairs RedAz + OxAz OxAz + RedAz CuI CuII CuII CuI for azurin k = 1.3 x 106 M-1 s-1

  3. Artificial Donor-Acceptor Pairs Cytochrome c; Fe---Ru, ~12 Å

  4. Method for Studying ET of Ru-Modified Proteins Rate ~ 30 s-1, T-independent

  5. Distance and Driving Force Dependencies of ET Rates

  6. Distance Dependence from the TDATerm for Reaction Center

  7. Distance dependence from the TDA term for Ru-modified cytochrome c b from the slope is 1.4 Å-1. Get a 10-fold decrease in rate for every 1.7 Å increase in distance For comparison, b for ET in vacuum is 2.8 Å-1 and b for ET through covalent bonds is 0.7 Å-1 (thanks to Brian Crane for the plot)

  8. Driving Force Dependence Data are from ruthenium-modified cytochrome c derivatives (upper) and a series of covalently linked donor/acceptor compounds

  9. The Mineral Springs in Bath, England, Source of Methylococcus capsulatus (Bath) The Restutive Contents of the WATER’s Concoctive Power: Solution of gaffes, chaos of Salts and mineral effluvia of subterranean expiration. It cleanses the body from all blotches, scurvicial itchings and BREAKING OUTS WHATSOEVER!

  10. NMR Structure of the Fd Domain of MMOR Mueller, Biochemistry, 41, 42-51 (2002)

  11. Each trace is fit as a sum of exponentials giving rise to the reported rate constants.

  12. These rate constants support the analysis with the full MMOR (Blazyk & Lippard, 2000)

  13. Electron Transfer from Flavin Domain to Fd Domain Electron transfer between the two disconnected flavin and iron/sulfur domains occurs but at a significantly reduced rate compared to the intact MMOR protein. (Blazyk & Lippard, 2000)

  14. For comparison, ET from 3-electron reduced MMOR to MMOH is characterized by apparent rate constants of 100 and 16 s-1.

  15. Summary - Points to Remember • Three major metallic units transfer electrons in bioinorganic chemistry: iron-sulfur clusters; blue copper including the dinuclear CuA; and cytochromes (iron porphyrins). • Electrons can transfer over long distances in ~10-15 Å hops . The rate depends on driving force, distance, and orientation of the reacting partners. Pathways are important (s > p > H-bonds according to theoretical models). • Electron transfer within and between proteins is optimized to take advantage of the molecular switching stations. Included are organic units such as flavins and inorganic units such as iron-sulfur clusters, both used in the MMOR protein.

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