Electron transfer in ruthenium-modified proteins

Abstract

Photochemical techniques have been used to measure the kinetics of intramolecular electron transfer in Ru(bpy)2(im)(His)2(+)-modified (bpy = 2,2'-bipyridine; im = imidazole) cytochrome c and azurin. A driving-force study with the His33 derivatives of cytochrome c indicates that the reorganization energy (lambda) for Fe2+-->Ru3+ ET reactions is 0.8 eV. Reductions of the ferriheme by either an excited complex, *Ru2+, or a reduced complex, Ru+, are anomalously fast and may involve formation of an electronically excited ferroheme. The distance dependence of Fe2+-->Ru3+ and Cu+-->Ru3+ electron transfer in 12 different Ru-modified cytochromes and azurins has been analyzed using a tunneling-pathway model. The ET rates in 10 of the 12 systems exhibit an exponential dependence on metal-metal separation (decay constant of 1.06 A-1) that is consistent with prediction of the pathway model.

Integrity of thermus thermophilus cytochrome c552 Synthesized by escherichia coli cells expressing the host‐specific cytochrome c maturation genes, ccmABCDEFGH: Biochemical, spectral, and structural characterization of the recombinant protein

“…Although studied for many decades as part of the cell's respiratory apparatus~Lemberg & Barrett, 1973;Mathews, 1985;Pettigrew & Moore, 1987!, cytochromes c remain of considerable interest as objects in the study of electron transfer reactions~Ferguson-Miller et al, 1979;Pan et al, 1993;Bjerrum et al, 1995;Geren et al, 1995;Winkler et al, 1995! and of protein folding~Sosnick et al, 1994;Bryngelson et al, 1995;Mines et al, 1996;Bai, 1999!.…”

Effect of protein dynamics on biological electron transfer

“…Much effort, therefore, has been directed toward understanding transport properties of various biological materials. In particular, recent experimental studies have provided information on the distance and structural dependence of electron transfer rates in various natural and modified proteins (1)(2)(3)(4). In these systems, electron transfer typically occurs over distances of 10-30 Å and is due to tunneling mediated by the intervening medium between donor and acceptor.…”

“…In this picture, the overall rate of electron transfer is proportional to the frequency at which donor and acceptor states come to resonance and the probability to transfer an electron between donor and acceptor states at the transition state (i.e., donoracceptor resonance) of the reaction. Such a direct application of classic Marcus theory has been very successful in characterizing major factors that control biological electron transfer (1)(2)(3)(4)(5).…”

Perspectives for Photobiology in Molecular Solar Fuels

“…[64][65][66] There are also examples of attached Ru complexes involving iron-sulfur proteins and myoglobin. [67,68] Photoactive porphyrins have been studied in b-type cytochromes when haem is first removed [69] and then replaced with zinc and iron porphyrins. [70,71] In apo-cytochrome b 562 , binding of zinc-chlorin e 6 (ZnCe 6 ) has been studied as ZnCe 6 has a long-lived excited state.…”