title: Spectroscopic studies on heme d in the visible and infrared.
abstract: Heme d has been isolated from the terminal oxidase complex of Escherichia coli strain MR43L/F152 and purified by high-pressure liquid chromatography. The infrared spectrum indicated that carbonyls in the chlorin skeleton of this isolated heme existed as carboxylic acids. Earlier work on the iron-free chlorin had demonstrated the presence of a spirolactone substituent. This may have arisen from a cyclization reaction from a dicarboxylic acid, diol precursor. Although the free heme in extracts can exist as a diol, this does not prove that the diol as such is the precise form in the enzyme complex. Visible and fluorescence spectra are reported for a variety of derivatives and complexes of heme d to establish a spectral library that may be used to prove the presence of this structure in other enzymes or cells. Association constants have been measured for complexes of heme d with cyanide, imidazole, and pyridine and are contrasted to available data for protoheme.
mesh_terms: D001665:Binding Sites; D005583:Fourier Analysis; D006418:Heme / Q000031:analogs & derivatives* / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D012996:Solutions; D012997:Solvents; D013053:Spectrophotometry; D013055:Spectrophotometry, Infrared
chemical_list: D012996:Solutions; D012997:Solvents; D006418:Heme; C029400:heme d1