title: Design of photoactive ruthenium complexes to study electron transfer and proton pumping in cytochrome oxidase.
abstract: This review describes the development and application of photoactive ruthenium complexes to study electron transfer and proton pumping reactions in cytochrome c oxidase (CcO). CcO uses four electrons from Cc to reduce O(2) to two waters, and pumps four protons across the membrane. The electron transfer reactions in cytochrome oxidase are very rapid, and cannot be resolved by stopped-flow mixing techniques. Methods have been developed to covalently attach a photoactive tris(bipyridine)ruthenium group [Ru(II)] to Cc to form Ru-39-Cc. Photoexcitation of Ru(II) to the excited state Ru(II*), a strong reductant, leads to rapid electron transfer to the ferric heme group in Cc, followed by electron transfer to Cu(A) in CcO with a rate constant of 60,000s(-1). Ruthenium kinetics and mutagenesis studies have been used to define the domain for the interaction between Cc and CcO. New ruthenium dimers have also been developed to rapidly inject electrons into Cu(A) of CcO with yields as high as 60%, allowing measurement of the kinetics of electron transfer and proton release at each step in the oxygen reduction mechanism.
authors.affiliation: Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR, USA. bdurham@uark.edu
authors.forename: Bill
authors.initials: B
authors.lastname: Durham
authors.forename: Francis
authors.initials: F
authors.lastname: Millett
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000528:radiation effects; D002417:Cattle; D045304:Cytochromes c / Q000737:chemistry / Q000378:metabolism; D004579:Electron Transport / Q000528:radiation effects; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction / Q000528:radiation effects; D011522:Protons; D012428:Ruthenium / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009942:Organometallic Compounds; D011522:Protons; D012428:Ruthenium; D045304:Cytochromes c; D003576:Electron Transport Complex IV