title: Coordination geometry of Cu-porphyrin in Cu(II)-Fe(II) hybrid hemoglobins studied by Q-band EPR and resonance Raman spectroscopies.
abstract: Cu(II)-Fe(II) hybrid hemoglobins were investigated by UV-vis, Q-band (35 GHz) EPR and resonance Raman spectroscopies. EPR results indicated that Cu-porphyrin in alpha-subunit within hybrid hemoglobin had either 5- or 4-coordination geometry depending on the pH conditions, while Cu-porphyrin in beta-subunit had only 5-coordination geometry at high and low pH values. These results were consistent with UV-vis absorption results. A new resonance Raman band appeared around 190 cm(-1), which was present whenever 5-coordinated Cu-porphyrin existed in Cu(II)-Fe(II) hybrid hemoglobins irrespective of the coordination number in Fe(II) subunit. This Raman band might be assigned to Cu-N(epsilon) (His) stretching mode. These results are direct demonstration of the existence of coordination changes of Cu-porphyrin in alpha-subunit within hybrid hemoglobin by shifting the molecular conformation from fully unliganded state to intermediately liganded state.
authors.affiliation: Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Balan
authors.initials: B
authors.lastname: Venkatesh
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hori
authors.forename: Gentaro
authors.initials: G
authors.lastname: Miyazaki
authors.forename: Shigenori
authors.initials: S
authors.lastname: Nagatomo
authors.forename: Teizo
authors.initials: T
authors.lastname: Kitagawa
authors.forename: Hideki
authors.initials: H
authors.lastname: Morimoto
mesh_terms: D003300:Copper / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D006454:Hemoglobins / Q000737:chemistry*; D011524:Protoporphyrins / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
chemical_list: D006454:Hemoglobins; D011524:Protoporphyrins; C092553:copper protoporphyrin IX; D003300:Copper