SYNTHESIS AND PHYSICAL CHARACTERIZATION OF NOVEL HEME-BASED MODEL SYSTEMS FOR PHOTOINITIATED ELECTRON-TRANSFER .2. DIRECT RUTHENATION OF MICROPEROXIDASE-11

This paper describes the design, synthesis, and initial characterizati on of a second type of model electron transfer system based upon micro peroxidase-11 (MP-11) that differs significantly from those described in the preceding article. In this system, a photoactive ruthenium tris (bipyridyl) donor is covalently attached directly to MP-11. Peptide di gestion followed by chromatographic analysis was used to establish tha t the ruthenium moiety bonds to the lysine residue of the MP-11 peptid e. This arrangement eliminates complications arising from the equilibr ium complexation of ruthenium donor and heme acceptor required for the model systems described in the previous article and leaves an axial p osition in the octahedral geometry of the heme iron open for ligation. Various optical spectroscopies and molecular modeling calculations we re employed to characterize the equilibrium properties and interchromo phore interactions of RuMP-11. Preliminary luminescence-quenching, tra nsient absorption, and transient resonance Raman studies demonstrated that rapid reversible electron transfer can be photoinitiated in this system.