PHOTOPERTURBATION OF THE HEME A(3)-CU-B BINUCLEAR CENTER OF CYTOCHROME-C-OXIDASE CO COMPLEX OBSERVED BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Purified cytochrome c oxidase CO complex from beef heart has been stud ied by Fourier transform infrared absorbance difference spectroscopy. Photolysis at 10-20 Kelvin results in dissociation of a(3)FeCO, format ion of CuBCO, and perturbation of the a(3)-heme and Cu-B complex. The vibrational perturbation spectrum between 900 and 1700 cm(-1) contains a wealth of information about the binuclear center. Appearance in inf rared photoperturbation difference spectra of virtually all bands prev iously reported from resonance Raman spectra indicate the importance o f polarization along the 4-vinyl:8-formyl axis, which results in the r eduction of heme symmetry to C-2v. Frequency-shifted bands due to the 8-formyl and 4-vinyl groups of the a(3)-heme have been identified and quantitated. The frequency shifts have been interpreted as being due t o a change in porphyrin polarization with change in spin state of the iron by photodissociation of CO or perturbation of the Cu-B coordinati on complex.