This research is focused on the interactions of oligopeptides with metalloporphyrins. The goal of this research is to construct both structural and functional models of heme proteins such as the cytochromes. Specifically, we are working on the binding of amphiphilic peptides to iron coproporphyrin (I) and measuring the binding constants, redox potentials, thermodynamic parameters, EPR spectra, and circular dichroism spectra. From Optical titrations and EPR, we have found that two peptides bind to the iron center of the porphyrin. The EPR spectra have revealed that the complexes are in fact low spin, S = 1/2, Fe(III) centers. This work should result in the publication of a communication in the near future. We are also working on the characterization of complexes of amphiphilic peptides with ruthenium porphyrins. Future work with the iron porphyrin includes design of a peptide which will form a 1:1 complex and working with negatively charged peptides (our peptides currently are positively charged at pH = 7). The ruthenium porphyrin/peptide complexes will be used to probe the dynamics of peptide folding. Kinetic studies will be done using VT-NMR while the thermodynamics of peptide folding. Kinetic studies will be done using VT-NMR while the thermodynamics will be investigated using circular dichroism by measuring molar ellipticities in the presence of denaturants like guanidine hydrochloride. Long term goals include developing synthetic electron transfer proteins, and examining intromolecular electron transfer.
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