Mitchell W. Mutz, James F. Wishart and George L. McLendon
Adv. Chem Ser. 254, Ch. 10, pp. 145-159
Abstract:
We prepared three bifunctional redox protein maquettes based on 12-, 16-, and 20-mer three-helix bundles. In each case, the helix was capped with a Co(III) tris-bipyridyl electron acceptor and also functionalized with a C-terminal viologen (1-ethyl-1'-ethyl-4,4'-bipyridinium) donor. Electron transfer (ET) was initiated by pulse radiolysis and flash photolysis and followed spectrometrically to determined average, concentration-independent, first-order rates for the 16-mer and 20-mer maquettes. For the 16-mer bundle, the alpha-helical content was adjusted by the addition of urea or trifluoroethanol to solutions containing the metalloprotein. This conformational flexibility under different solvent conditions was exploited to probe the effects of helical secondary structure on ET rates. In addition to describing experimental results from these helical systems, this chapter discuss several additional metalloprotein models from the recent literature.