title: Resonance Raman investigation of nitric oxide bonding in nitrosylhemoglobin A and -myoglobin: detection of bound N-O stretching and Fe-NO stretching vibrations from the hexacoordinated NO-heme complex.
abstract: With excitation at 406.7 nm, we have observed the resonance Raman enhancement of the bound v(N-O) stretch at approximately 1623 cm-1 in nitrosylhemoglobin A and nitrosylmyoglobin, indicating the existence of a charge-transfer transition underlying the strong Soret band. The v(Fe-NO) stretch at 551 cm-1 has also been detected in the Soret as well as in the Q-band region, a phenomenon similar to the v(Fe-O2) and v(Fe-CO) stretches in oxy and carbon monoxy hemoproteins. It appears that these iron-ligand vibrations ay be resonance enhanced via porphyrin pi leads to pi transitions. Upon addition of inositol hexaphosphate at pH 6.0, the v(Fe-NO) stretch at 551 cm-1 and a low-frequency mode at 301 cm-1 exhibit an intensity decrease by approximately one-half. Contrary to the work of Stong et al. [Stong, J. D., Burke, J. M., Daly, P., Wright. P., & Spiro, T. G. (1980) J. Am. Chem. Soc. 102, 5815], who employed an excitation wavelength at 454.5 nm, we observed no intensity increase at 592 cm-1 attributable to the v(Fe-NO) stretch from the pentacoordinated NO-heme complex in the alpha subunits.
mesh_terms: D000818:Animals; D004735:Energy Transfer; D006418:Heme / Q000032:analysis; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D007501:Iron / Q000032:analysis*; D009211:Myoglobin / Q000031:analogs & derivatives* / Q000032:analysis; D009569:Nitric Oxide / Q000032:analysis*; D009603:Nitroso Compounds / Q000032:analysis; D013059:Spectrum Analysis, Raman; D014907:Whales
chemical_list: D006454:Hemoglobins; D009211:Myoglobin; D009603:Nitroso Compounds; C031560:myoglobin nitroxide; C008657:nitrosyl hemoglobin; D009569:Nitric Oxide; D006418:Heme; D007501:Iron