Rates of heme oxidation and reduction in Ru(His33)cytochrome c at very high driving forces

Gary A. Mines; Morten J. Bjerrum; Michael G. Hill; Danilo R. Casimiro; I. Jy Chang; Jay R. Winkler; Harry B. Gray

doi:10.1021/ja9519243

Rates of heme oxidation and reduction in Ru(His33)cytochrome c at very high driving forces

Gary A. Mines
, Morten J. Bjerrum
, Michael G. Hill
, Danilo R. Casimiro
, I. Jy Chang
, Jay R. Winkler
, Harry B. Gray^*

^*Corresponding author for this work

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

116 Citations (Scopus)

Abstract

The rates of Ru(His33)cytochrome c electron-transfer (ET) reactions have been measured over a driving-force range of 0.59 to 1.89 eV. The driving-force dependence of Fe²⁺ → Ru³⁺ ET in RuL₂(im)(His33)cyt c [L = 2,2'-bipyridine (bpy), 4,4',5,5'-tetramethyl-2,2'-bipyridine (4,4',5,5'-(CH₃)₄-bpy), 4,4'-dimethyl-2,2'-bipyridine (4,4'-(CH₃)₂-bpy), 4,4'-bis(N-ethylcarbamoyl)-2,2'-bipyridine (4,4'-(CONH(C₂H₅))₂-bpy), 1,10-phenanthroline (phen); im = imidazole] is well described by semiclassical ET theory with k(max) = 2.7 x 10⁶ s^-1 (H(AB) = 0.095 cm^-1) and λ = 0.74 eV. As predicted by theory, the rate of an exergonic (-ΔG° = 1.3 eV) heme reduction reaction, *Ru²⁺(bpy)₂(im)(His) → Fe³⁺, falls in the inverted region (k = 2.0 x 10⁵ s^-1). In contrast, the rates of three highly exergonic heme reductions, *Ru²⁺(phen)₂(CN)(His) → Fe³⁺ (2.0 x 10⁵ s^-1; 1.40 eV), Ru⁺(4,4'-(CONH(C₂H₅))₂-bpy)₂(im)(His) → Fe³⁺ (2.3 x 10⁵ s^-1; 1.44 eV), and Ru⁺(phen)₂(CN)(His)→ Fe³⁺ (4.5 x 10⁵ s^-1; 1.89 eV), are much higher than expected for reactions directly to ground-state products. Agreement with theory is greatly improved by assuming that an electronically excited ferroheme (Fe²⁺ → *Fe²⁺; ~1.05 eV) is the initial product in each of these reactions.

Original language	English
Pages (from-to)	1961-1965
Number of pages	5
Journal	Journal of the American Chemical Society
Volume	118
Issue number	8
DOIs	https://doi.org/10.1021/ja9519243
Publication status	Published - 1996 Feb 28

ASJC Scopus subject areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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@article{6bff64157af244aeb76e08edda960732,

title = "Rates of heme oxidation and reduction in Ru(His33)cytochrome c at very high driving forces",

abstract = "The rates of Ru(His33)cytochrome c electron-transfer (ET) reactions have been measured over a driving-force range of 0.59 to 1.89 eV. The driving-force dependence of Fe2+ → Ru3+ ET in RuL2(im)(His33)cyt c [L = 2,2'-bipyridine (bpy), 4,4',5,5'-tetramethyl-2,2'-bipyridine (4,4',5,5'-(CH3)4-bpy), 4,4'-dimethyl-2,2'-bipyridine (4,4'-(CH3)2-bpy), 4,4'-bis(N-ethylcarbamoyl)-2,2'-bipyridine (4,4'-(CONH(C2H5))2-bpy), 1,10-phenanthroline (phen); im = imidazole] is well described by semiclassical ET theory with k(max) = 2.7 x 106 s-1 (H(AB) = 0.095 cm-1) and λ = 0.74 eV. As predicted by theory, the rate of an exergonic (-ΔG° = 1.3 eV) heme reduction reaction, *Ru2+(bpy)2(im)(His) → Fe3+, falls in the inverted region (k = 2.0 x 105 s-1). In contrast, the rates of three highly exergonic heme reductions, *Ru2+(phen)2(CN)(His) → Fe3+ (2.0 x 105 s-1; 1.40 eV), Ru+(4,4'-(CONH(C2H5))2-bpy)2(im)(His) → Fe3+ (2.3 x 105 s-1; 1.44 eV), and Ru+(phen)2(CN)(His)→ Fe3+ (4.5 x 105 s-1; 1.89 eV), are much higher than expected for reactions directly to ground-state products. Agreement with theory is greatly improved by assuming that an electronically excited ferroheme (Fe2+ → *Fe2+; \textasciitilde{}1.05 eV) is the initial product in each of these reactions.",

author = "Mines, \{Gary A.\} and Bjerrum, \{Morten J.\} and Hill, \{Michael G.\} and Casimiro, \{Danilo R.\} and Chang, \{I. Jy\} and Winkler, \{Jay R.\} and Gray, \{Harry B.\}",

year = "1996",

month = feb,

day = "28",

doi = "10.1021/ja9519243",

language = "English",

volume = "118",

pages = "1961--1965",

journal = "Journal of the American Chemical Society",

issn = "0002-7863",

publisher = "American Chemical Society",

number = "8",

}

TY - JOUR

T1 - Rates of heme oxidation and reduction in Ru(His33)cytochrome c at very high driving forces

AU - Mines, Gary A.

AU - Bjerrum, Morten J.

AU - Hill, Michael G.

AU - Casimiro, Danilo R.

AU - Chang, I. Jy

AU - Winkler, Jay R.

AU - Gray, Harry B.

PY - 1996/2/28

Y1 - 1996/2/28

N2 - The rates of Ru(His33)cytochrome c electron-transfer (ET) reactions have been measured over a driving-force range of 0.59 to 1.89 eV. The driving-force dependence of Fe2+ → Ru3+ ET in RuL2(im)(His33)cyt c [L = 2,2'-bipyridine (bpy), 4,4',5,5'-tetramethyl-2,2'-bipyridine (4,4',5,5'-(CH3)4-bpy), 4,4'-dimethyl-2,2'-bipyridine (4,4'-(CH3)2-bpy), 4,4'-bis(N-ethylcarbamoyl)-2,2'-bipyridine (4,4'-(CONH(C2H5))2-bpy), 1,10-phenanthroline (phen); im = imidazole] is well described by semiclassical ET theory with k(max) = 2.7 x 106 s-1 (H(AB) = 0.095 cm-1) and λ = 0.74 eV. As predicted by theory, the rate of an exergonic (-ΔG° = 1.3 eV) heme reduction reaction, *Ru2+(bpy)2(im)(His) → Fe3+, falls in the inverted region (k = 2.0 x 105 s-1). In contrast, the rates of three highly exergonic heme reductions, *Ru2+(phen)2(CN)(His) → Fe3+ (2.0 x 105 s-1; 1.40 eV), Ru+(4,4'-(CONH(C2H5))2-bpy)2(im)(His) → Fe3+ (2.3 x 105 s-1; 1.44 eV), and Ru+(phen)2(CN)(His)→ Fe3+ (4.5 x 105 s-1; 1.89 eV), are much higher than expected for reactions directly to ground-state products. Agreement with theory is greatly improved by assuming that an electronically excited ferroheme (Fe2+ → *Fe2+; ~1.05 eV) is the initial product in each of these reactions.

AB - The rates of Ru(His33)cytochrome c electron-transfer (ET) reactions have been measured over a driving-force range of 0.59 to 1.89 eV. The driving-force dependence of Fe2+ → Ru3+ ET in RuL2(im)(His33)cyt c [L = 2,2'-bipyridine (bpy), 4,4',5,5'-tetramethyl-2,2'-bipyridine (4,4',5,5'-(CH3)4-bpy), 4,4'-dimethyl-2,2'-bipyridine (4,4'-(CH3)2-bpy), 4,4'-bis(N-ethylcarbamoyl)-2,2'-bipyridine (4,4'-(CONH(C2H5))2-bpy), 1,10-phenanthroline (phen); im = imidazole] is well described by semiclassical ET theory with k(max) = 2.7 x 106 s-1 (H(AB) = 0.095 cm-1) and λ = 0.74 eV. As predicted by theory, the rate of an exergonic (-ΔG° = 1.3 eV) heme reduction reaction, *Ru2+(bpy)2(im)(His) → Fe3+, falls in the inverted region (k = 2.0 x 105 s-1). In contrast, the rates of three highly exergonic heme reductions, *Ru2+(phen)2(CN)(His) → Fe3+ (2.0 x 105 s-1; 1.40 eV), Ru+(4,4'-(CONH(C2H5))2-bpy)2(im)(His) → Fe3+ (2.3 x 105 s-1; 1.44 eV), and Ru+(phen)2(CN)(His)→ Fe3+ (4.5 x 105 s-1; 1.89 eV), are much higher than expected for reactions directly to ground-state products. Agreement with theory is greatly improved by assuming that an electronically excited ferroheme (Fe2+ → *Fe2+; ~1.05 eV) is the initial product in each of these reactions.

UR - https://www.scopus.com/pages/publications/0029965935

UR - https://www.scopus.com/pages/publications/0029965935#tab=citedBy

U2 - 10.1021/ja9519243

DO - 10.1021/ja9519243

M3 - Article

AN - SCOPUS:0029965935

SN - 0002-7863

VL - 118

SP - 1961

EP - 1965

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 8

ER -

Rates of heme oxidation and reduction in Ru(His33)cytochrome c at very high driving forces

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