Iron chlorin-reconstituted histidine-ligated heme proteins as models for naturally occurring iron chlorin proteins: magnetic circular dichroism spectroscopy as a probe of iron chlorin coordination structure

Electronic absorption and magnetic circular dichroism (MCD) spectroscopic experiments help characterize iron methylchlorin- and mesochlorin-reconstituted myoglobin, horseradish peroxidase and cytochrome b5. A comparative study of these spectra with those of corresponding iron octaethylchlorin complexes helps derive spectral signatures for histidine-ligated iron chlorin-containing proteins. MCD spectroscopy is an efficient technique to determine iron chlorin coordination structure, spin state and oxidation state, and to differentiate two types of green heme systems, iron-chlorins and iron formyl-substituted porphyrins.