FIGURE 5.

Spectral changes of the Y181N variant after the addition of H₂O₂ measured with diode array spectrophotometer. A, spectrum of 3.3 μm Y181N in 20 mm sodium succinate buffer (pH 4.5) containing 1 mm CaCl₂ (resting state, dashed line), and spectral changes of Y181N during the 2–120-s period after the addition of 4.9 μm H₂O₂ (solid lines), indicating Compound I self-reduction to Compound II (spectra acquired at 2 s, and then each 20 s) (inset, 416-nm trace showing Compound I decay). B, spectrum of resting Y181N (dashed line), and spectral changes of Y181N obtained during the 180–900-s period after H₂O₂ addition, indicating Compound II self-reduction to resting state (spectra acquired at 180 s, and then each 120 s). Details (×4 absorbance) of the 450–700 nm region are shown.