FIGURE 8.
Proposed reaction pathway of HsDodA leading to the fast depopulation of the excited state of riboflavin (Rf). After the photoexcitation, an electron transfer from a tryptophan residue (W) to riboflavin and a proton transfer from a surrounding water to N5 of riboflavin occurs faster than the time resolution of the instrumental setup. Electron- and proton back-transfer with the time constant τ2 result in the initial ground state. In a second parallel reaction pathway, depopulation of the excited state of the flavin results in an intermediate (IS) with yet unknown identity. It decays with the time constant τ3 to the initial ground state.