Tryptophan ¹³C nuclear-spin polarization generated by intraprotein electron transfer in a LOV2 domain of the blue-light receptor phototropin

¹³C-NMR experiments were performed on photo-excited fully and partially ¹³C-labelled LOV2 domains of the blue-light receptor phototropin. In the present paper, we report on nuclear-spin polarized tryptophan resonances that are generated by light-induced intraprotein electron transfer to the FMN cofactor. The spectra are discussed with respect to earlier data obtained from ¹³C-NMR experiments on unlabelled LOV2 domains that have been reconstituted with FMN ¹³C isotopologues.