Resonance Raman studies on enzymatic intermediates of heme proteins and model compounds

Ki-Jung Paeng, Marquette University


The essential goal of HRP and catalase research is to gain an understanding of the conformations and mechanisms of enzymatic reactions in which the protein matrix regulates heme reactivity. A doubly oxidized heme (metalloporphyrin) has been proposed as a reactive intermediate in the catalytic cycles of peroxidases and catalases, and it has been suggested to be a free radical porphyrin species. The major accomplishments of this research were summarized as follows: (1) The RR spectra for HRP I was obtained by low power laser excitation and microdroplet stream. $\nu$(Fe-O) was located at 737 cm$\sp{-1}$ and is 39 cm$\sp{-1}$ downshift from HRP II. The high frequency spectra confirms the A$\sb{\rm 2u}$ ground state of HRP I. (2) The RR spectra of Cat I and II were obtained with excitation by 406.7 nm laser line. $\nu$(Fe-O) of Cat II was located at 797 cm$\sp{-1}$ and Cat I at 805 cm$\sp{-1}$. $\Delta\nu$ between Cat I and Cat II is +8 cm$\sp{-1}$. The high frequency spectra of Cat II shows low spin ferryl heme and Cat I is A$\sb{\rm 1u}$ ground state. (3) The RR spectra of $\pi$ cation radical complexes of Fe(TMP) was obtained in $-$78$\sp\circ$C. The photodegradation of cation radical species in presence of methanol was studied. The new intermediate was found at reaction between ferryl cation radical species and substrates. (4) An effective mixing method which originally suggested by Clegg et. al. has been modified and characterized.

Recommended Citation

Paeng, Ki-Jung, "Resonance Raman studies on enzymatic intermediates of heme proteins and model compounds" (1989). Dissertations (1962 - 2010) Access via Proquest Digital Dissertations. AAI9014059.