Cryoradiolytic reduction of an oxyferrous cytochrome P450cam crystal at 140 K. (a) UV-Vis absorption spectra of P450cam during irradiation with an unfocused X-ray beam. New peaks at 443 and 563 nm are formed, and the Soret band shifts first to the red (hydroperoxo complex formation), then to the blue (reduction). (b) UV-Vis spectra after different times of irradiation. (c) Time course of the 443 nm peak. To obtain only the height of the peak, the arithmetic mean of the absorbances at 426 nm and 459 nm was subtracted (see Fig. 8a).