Long-range electron transfer in ruthenium-labelled myoglobin

by Karas, Jennifer Lynn

Abstract (Summary)
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. 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; [delta]E°=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 ([delta]E°=0.02 V), to 3x10(5) s-1 for ZnP*[...]RuIII in a4isnRu(His48)MbZn ([delta]E°=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.
Bibliographical Information:

Advisor:Harry B. Gray; Jay Richmond Winkler; David M. Dooley

School:California Institute of Technology

School Location:USA - California

Source Type:Master's Thesis



Date of Publication:09/09/1988

© 2009 All Rights Reserved.