Low frequency vibrational modes of oxygenated myoglobin, hemoglobins, and modified derivatives.
The low frequency resonance Raman spectra of the dioxygen adducts of myoglobin, hemoglobin, its isolated subunits, mesoheme-substituted hemoglobin, and several deuteriated heme derivatives are reported. The observed oxygen isotopic shifts are used to assign the iron-oxygen stretching (approximately 570 cm-1) and the heretofore unobserved delta (Fe-O-O) bending (approximately 420 cm-1) modes. Although the delta (Fe-O-O) is not enhanced in the case of oxymyoglobin, it is observed for all the hemoglobin derivatives, its exact frequency being relatively invariable among the derivatives. The lack of sensitivity to H2O/D2O buffer exchange is consistent with our previous interpretation of H2O/D2O-induced shifts of v(O-O) in the resonance Raman spectra of dioxygen adducts of cobalt-substituted heme proteins; namely, that those shifts are associated with alterations in vibrational coupling of v(O-O) with internal modes of proximal histidyl imidazole rather than to steric or electronic effects of H/D exchange at the active site. No evidence is obtained for enhancement of the v(Fe-N) stretching frequency of the linkage between the heme iron and the imidazole group of the proximal histidine.
Jeyarajah
S
S
Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233.
Proniewicz
L M
LM
Bronder
H
H
Kincaid
J R
JR
D006418:Heme / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D009211:Myoglobin / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D013059:Spectrum Analysis, Raman
D006454:Hemoglobins; D009211:Myoglobin; D006418:Heme; D010100:Oxygen