(A) Electronic absorption spectra of ferric, ferric/BHA, ferrous and cyanide-bound species of HRP. The Soret maxima are located at 402, 408, 437, and 423 nm, respectively. (B) Electronic absorption spectra of ferric and ferrous species of HRP-NO. The Soret maxima are located at 422 nm. (C) Electronic absorption spectra of ferric, ferric H64L, ferric fluoride-bound, ferrous, and cyanide-bound species of Mb measured. The Soret maxima are located at 409, 390, 408, 435, and 423 nm, respectively. (D) Electronic absorption spectra of ferric, ferrous, and cyanide-bound species of Cgb. The Soret maxima are located at 398, 432, and 418 nm, respectively. All spectra in Figure 1 are measured at room temperature.