Coordination geometry of Cu-porphyrin in Cu(II)-Fe(II) hybrid hemoglobins studied by Q-band EPR and resonance Raman spectroscopies.
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.
Venkatesh
Balan
B
Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Hori
Hiroshi
H
Miyazaki
Gentaro
G
Nagatomo
Shigenori
S
Kitagawa
Teizo
T
Morimoto
Hideki
H
D003300:Copper / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D006454:Hemoglobins / Q000737:chemistry*; D011524:Protoporphyrins / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
D006454:Hemoglobins; D011524:Protoporphyrins; C092553:copper protoporphyrin IX; D003300:Copper