Figure 2.

Spectrum of the intermediate detected in the oxidative half-reaction. An anaerobic solution of reduced WT ThyX (14 μM active sites, after mixing) and dUMP (300 μM) in 0.1 M Tris-HCl (pH 8.0) and 1 mM EDTA was mixed with 400 μM CH₂THF and 15 mM formaldehyde using a stopped-flow spectrophotometer in diode-array mode. (A) Stereoview of spectra as a function of time. Spectra were recorded with an integration time of 1.5 ms at various intervals out to 10 s. Note the logarithmic time scale. (B) Deconvoluted intermediate spectra calculated by singular-value decomposition using the raw data in panel A and a two-step mechanism, giving rate constants of 28.4 and 0.2 s^–1.