Figure 2.

Flavin photoreduction of cry1 Trp triad mutants in whole cell extracts. Whole cell lysates from cultures expressing Arabidopsis cry1 wild type, W400F or W324F mutants were illuminated for 1 min with white light (600 μmolm⁻²sec⁻¹) in PBS pH7.5, 5 mM DTT. Spectra taken after illumination were substracted from dark spectra to provide the (Dark minus Light) difference spectra shown in the figure, indicating the reduction of flavin from oxidized to radical (FADH°) state. No difference in absorption was seen under these conditions in whole cell extracts that were not expressing cryptochrome proteins (control cells).