Kinetics of NO rebinding to the ferrous (A) and ferric (B) GAF domains of DosS (red) and DosT (blue), measured at the bleaching maxima at 418 nm (A) and 420 nm (B). The Insets show transient spectra for ferrous DosT-NO (A) at delay times of 0.4 ps (blue), 3 ps (black), 9 ps (green), 50 ps (red) and 300 ps (cyan) and ferric DosS-NO (B) at delay times of 0.8 ps (blue), 3 ps (black), 20 ps (green), 50 ps (red) and 300 ps (cyan).