Fig. 5

Absorption spectra of Limax xenopsin and Opn5A. a The absorption spectrum of xenospin in the dark (black curve) and after blue light irradiation (blue curve). (inset) The difference absorption spectra generated by subtracting absorbance at each wavelength before from after blue light irradiation (blue curve), before from after subsequent orange light irradiation (magenta curve), and before from after subsequent second blue light irradiation (green curve). The green curve was the mirror image of the magenta curve, indicating the bistability of xenopsin. b The absorption spectrum of Opn5A (black curve) fitted with the rhodopsin nomogram that has an absorption maximum of ~ 500 nm (red curve). Note that absorbance under 430 nm may be affected by scattering from impurities