| 165836 |
Wagner GC, Kassner RJ: Spectroscopic properties of ferrous heme complexes of sterically hindered ligands. Biochim Biophys Acta. 1975 Jun 12;392(2):319-27.
Mesoheme IX complexes of sterically hindered ligands 2-methylimidazole, tert-butylamine and 2-methylpyridine in aqueous glycerol solutions are characterized by broad visible absorption spectra at ambient temperature exhibiting close similarities to high-spin ferrous hemeproteins. Spectrophotometric titrations of mesoheme IX with these ligands indicate well-defined equilibria for 2-methylimidazole and tert-butylamine corresponding to the formation of penta-coordinate strong-field ligand complexes. Variable temperature spectra of these complexes from ambient to 77 degrees K exhibit a change to hemochrome spectra characteristic of the low-spin unhindered ligand complexes. Corresponding changes in the visible spectra are not observed for the high-spin hemeproteins deoxymyoglobin, horse-radish peroxidase and cytochrome c. The appropriate utilization of these hindered ligand heme complexes as model systems for high-spin ferrous hemeproteins has been discussed. |
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