Studies on the origin of the near-infrared (800–900 nm) absorption of cytochrome c oxidase

Proton Translocation in Proteins

“…The weak (e = 2 mM-~ cm-~) near IR band seen ca. 830 nm in the oxidized enzyme's spectrum has been suggested to arise exclusively from CuA, and has been assigned to a ligand-to-metal charge transfer transition involving CUA and a sulfur ligand (41). This band disappears in the fully reduced and CN-bound, mixed-valence enzyme, consistent with the above assignment.…”

Structural features of the copper‐depleted cytochrome oxidase from beef heart: iron exafs

“…Optical studies have been similarly difficult to interpret, the main absorption band in the near infrared region being attributed to Cu a [3] which is closely linked to the g = 2 EPR signal [3,4]. The optical transition, attributable to EPR undetectable copper, has been regarded by some to be scarcely detectable [3] but has been observed by us under several experimental conditions [5,6].…”

Effect of Indomethacin on Cerebral Oxidized Cytochrome Oxidase in Preterm Infants

“…Precise determination of changes in [CytOz] requires accurate data for the absorption spectra of all mobile chromophores present and validity of the modified Beer-Lambert relationship. Near infrared spectra for Hb have now been measured under carefully controlled conditions by several groups (6,10,20), and spectra for cytochrome oxidase obtained both from Hbfree animals in vivo (10,21,22) and from purified cytochrome extracts (23). Recent studies have shown that spectra measured in vivo and in vitro are identical (6) and confirmed that the brain normally contains only three mobile chromophores (24).…”

“…Electrons pass to from cytochrorne c, and the oxidation levels of cytochrome c and CuA are similar under most conditions (32,33). Absorption of near-infrared light by cytochrome oxidase occurs almost entirely at the center, the oxidized form of CUA having a characteristic spectrum, whereas the reduced form has no distinguishable absorption (23). Near infrared measurements of changes in [CytOz] thus measure alterations in the concentration of oxygenated CuA and reflect the concentration of oxidized cytochrome c.…”