FIGURE 6.
Reduction of FMN bound to hIYD and the reference dye AQDS by xanthine/xanthine oxidase. Spectral changes were monitored every 2 min over a total of 120 min. Only a selected number of spectra are illustrated for clarity, and the arrows indicate the direction of the absorbance change. The concentration of reduced AQDS was measured at 325 nm, an isosbestic point for hIYD, and conversely the concentration of reduced hIYD was measured at 355 nm, an isosbestic point of AQDS. Inset, the linear best fit of log(FMNox/FMNhq) versus log(AQDSox/AQDSred) was used to calculate the midpoint potential (24, 25).