title: Visible absorption spectra of quantum mixed-spin ferric heme proteins.
abstract: Recently, it has been shown that the magnetic data for Chromatium ferricytochrome c' at pH 7 are consistent with quantum mechanically (as distinguished from thermally) mixed mid-spin (S = 3/2) and high-spin (S = 5/2) heme. Visible absorption spectra of the protein measured at 77 degrees K and 293 degrees K, pH 7, show peaks at 400, 490, and 632 nm. The observation of a 630 nm band in quantum mixed-spin heme spectra, and the spin state-dependence of the band intensity, are discussed in the context of the iron-ligand structure for quantum mixed-spin heme inferred from magnetic data.
mesh_terms: D002844:Chromatium / Q000201:enzymology; D003574:Cytochrome c Group; D004578:Electron Spin Resonance Spectroscopy; D005615:Freezing; D006418:Heme; D011487:Protein Conformation; D011789:Quantum Theory; D013053:Spectrophotometry
chemical_list: D003574:Cytochrome c Group; D006418:Heme