Vibrational structure of the formyl group on heme a. Implications on the properties of cytochrome c oxidase.
Resonance Raman spectra have been recorded for heme a derivatives in which the oxygen atom of the formyl group has been isotopically labeled and for Schiff base derivatives of heme a in which the Schiff base nitrogen has been isotopically labeled. The 14N-15N isotope shift in the C = N stretching mode of the Schiff base is close to the theoretically predicted shift for an isolated C = N group for both the ferric and ferrous oxidation states and in both aqueous and nonaqueous solutions. In contrast, the 16O-18O isotope shift of the C = O stretching mode of the formyl group is significantly smaller than that predicted for an isolated C = O group and is also dependent on whether the environment is aqueous or nonaqueous. This differences between the theoretically predicted shifts and the observed shifts are attributed to coupling of the C = O stretching mode to as yet unidentified modes of the heme. The complex behavior of the C = O stretching vibration precludes the possibility of making simple interpretations of frequency shifts of this mode in cytochrome c oxidase.
Han
S W
SW
AT&T Bell Laboratories, Murray Hill, New Jersey 07974.
Ching
Y C
YC
Hammes
S L
SL
Rousseau
D L
DL
D003576:Electron Transport Complex IV / Q000378:metabolism*; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D008968:Molecular Conformation; D012545:Schiff Bases; D013059:Spectrum Analysis, Raman / Q000379:methods; D014732:Vibration
D012545:Schiff Bases; D006418:Heme; D003576:Electron Transport Complex IV