Modern Approaches to the Study of Cytochrome Oxidase

Spectroscopic characterization of compound C and related derivatives of cytochrome oxidase.

“…We therefore expect that a and a3 will contribute comparable intensities to the RR spectrum regardless of differences in spin state. This is observed to be the case in fully reduced enzyme (19), in which both hemes have their Soret maximum at 443 nm and exhibit extreme differences in spin state (1, 4). Furthermore, the relative intensity of the 1676 cm-1 line attributed to a3 (20) argues against any drastic decrease in the resonance enhancement of a3 in these derivatives.…”

“…RR spectroscopy The RR spectra of cytochrome oxidase and some of these derivatives are shown in Fig. 2; someRaman frequencies are summarized in Table 1 (15,19). The core expansion region in the RR spectrum of resting oxidase shows two bands at 1572 cm-1 (h.s.…”

Resolution of the electronic transitions of cytochrome c oxidase: evidence for two conformational states of ferrous cytochrome alpha.

“…While the effects of this symmetry lowering have been observed for the vibronically allowed electronic transitions, no evidence for splitting of the Soret transition of heme A has been observed (23). If, however, the symmetry were further lowered by specific interactions with the protein, one might expect this splitting to be observed.…”

“…For heme groups with symmetric (or quasi-symmetric) placement ofperipheral groups on the tetrapyrrole ring system, the electronic spectrum reflects D4h effective symmetry (22,23).…”

“…In this point group, the degeneracy of the Eg lowest unoccupied molecular orbital should be lifted, resulting in two Soret transitions, one A, --B2g and one A, --B3g (23).…”