Spectral changes during the anaerobic reduction of FerBHis₆ by the xanthine/xanthine oxidase system.

The spectra shown (from top to bottom) were recorded at 0, 5, 10, 13, 17, 22, 26, 30 and 36 min for 48 µM FerBHis₆ (A) and 0, 5, 10, 15, 20, 24, 27, 30, 33, 37 and 40 min for 65 µM FerBHis₆ with 40 µM Indigo Carmine. In (B), the inset shows the log(ox/red) for the dye vs. that for the enzyme bound FMN revealing a slope of 1.08, which is close to the theoretical value of 1. The standard potential of FMN was calculated from the y-axis intercept.