Fig. 2: UV-Vis and EPR spectroscopy for wild-type TtCBD.
From: Redox driven B12-ligand switch drives CarH photoresponse
Photoconversion followed by UV-Vis spectroscopy under a aerobic and b anaerobic conditions in 50 mM Tris-HCl buffer (pH 7.5). The times indicated in the key refer to the length of time samples were incubated in the dark following illumination for 15 s. c Gradual conversion of Co(II) species to light-adapted state on exposure to O2 at room temperature. d Observed change in colour of the sample due to the formation of different Co oxidation states in solution during the photocycle. The hexacoordinate Co(III) state can have a 6th coordination as His or OHx ligand (x = 1 or 2). e The light-exposed anaerobic TtCBD samples were flash-frozen in liquid nitrogen following incubation in the dark at room temperature for various periods of time, with the corresponding cw-EPR spectra measured at 20 K confirming the formation of Co(II) species. f Annealing of the light-exposed, anaerobic TtCBD sample at RT shows a conversion of Co(II) to Co(III)-superoxo and subsequently to Co(III) light-adapted state as followed by EPR spectroscopy.
