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Long-Range Electron Transfer in Ruthenium-Labelled Myoglobin


Karas, Jennifer Lynn (1989) Long-Range Electron Transfer in Ruthenium-Labelled Myoglobin. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/pc6d-xe62.


The driving force dependence of electron-transfer (ET) reactions has been investigated in protein derivatives of the type trans-Ru(NH₃)₄L-myoglobin (L=NH₃, pyridine, isonicotinamide). In these species, the labelling sites of the ruthenium moiety were determined by proton NMR spectroscopy. ET rates have been measured from the iron(II)-heme in myoglobin to both a₅Ru (a=NH₃) and a₄pyRu (py=pyridine) acceptors bound to histidine 48 (kET=0.04 and 2.5 s⁻¹; ΔE°=0.02 and 0.275, respectively). These kinetic results demonstrate for the ruthenium-labelled Mb system that long-range ET is reversible and that the dependence of the ET rates on reaction free energy closely follows Marcus theory. ET rates were also determined for high driving-force systems that were prepared by substitution of palladium and zinc(mesoporphyrin IX), (PdP, ZnP) into the a₄LRu(His-48) derivatives of Mb. ET from the excited state MbMP* (M=Pd or Zn) to the ruthenium acceptor was measured by transient spectroscopy. Reverse ET rates from the surface RuII to the ZnP radical cation, (RuII→ZnP⁺) were also determined. The ET rates range from 0.04 s⁻¹ for FeII→RuIII ET in a₅Ru(His-48)MbFe (ΔE°=0.02 V), to 3x10⁵ s⁻¹ for ZnP*→RuIII in a₄isnRu(His48)MbZn (ΔE°=1.2 V). The driving force dependence of the ET rates in the ruthenium-labelled Fe, Zn and Pd(His-48)Mb derivatives has provided information on the reorganization energy. Using Marcus theory, a reorganization energy of 1.5(2) eV has been estimated.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Chan, Sunney I. (advisor)
  • Gray, Harry B. (co-advisor)
Thesis Committee:
  • Chan, Sunney I. (chair)
  • Bercaw, John E.
  • Marcus, Rudolph A.
  • Gray, Harry B.
Defense Date:9 September 1988
Record Number:CaltechETD:etd-06082007-092426
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2520
Deposited By: Imported from ETD-db
Deposited On:27 Jun 2007
Last Modified:13 Aug 2021 21:00

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