Portland State University. Department of Chemistry
Joann S. Loehr
Date of Publication
Master of Science (M.S.) in Chemistry
Organometallic compounds -- Spectra, Zinc, Raman spectroscopy
1 online resource (v, 40 pages : illustrations)
Cobalt-substituted carboxypeptidase and carbonic anhydrase were chosen as candidates for resonance Raman spectroscopy because they possess visible absorption due to the Co(II)-protein complex. However, no evidence for resonance-enhanced peaks due to the cobalt-containing chromophore was found with laser excitation near the visible absorption bands (514.5 nm) or closer to the ultraviolet absorption bands (457.9nm).
Arsanilazocarboxypeptidase and model azotyrosine compounds were selected for a Raman spectroscopic investigation because they have intense absorption bands in the visible region. All of these substances yielded similar resonance Raman spectra. Although there was no evidence for specific zinc-ligand vibrations, shifts in vibrational frequencies of the azotyrosine chromophore could be used as proof of zinc complexation. The protonated azotyrosine model compound was found to have the phenoxy group hydrogen bonded to the azo group, forming a six-membered ring. Replacement of the proton by zinc resulted in the zinc atom being bound only to the phenoxy group. In arsanilazocarboxypeptidase the azotyrosine at position 248 in the polypeptide chain was found to have a structure similar to the protonated model compound, a six-membered ring with zinc bridging the phenoxy group and the azo group. This gave further proof that Tyr 248 is close to the zinc atom in the native enzyme, even in the absence of substrate.
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Derry, Robert Edward, "Characterization of Zinc-containing Metalloproteins by Resonance Raman Spectroscopy" (1974). Dissertations and Theses. Paper 2167.