Electrochemically induced reduced minus oxidized ATR-FTIR difference spectra of bovine CcO. (A) High-frequency (3,875–3,560 cm-1) region (black). Data were fitted with a combination of four Gaussian components, each of 7–9 cm-1 FWHM (red trace; individual Gaussians shown in green); (B) 1,800–1,400 cm-1 region.