Absorption spectra of SaBphP1 constructs where the Pr to Pfr transition has been initiated with 660 nm light. Black solid line: illumination by 740 nm, black dashed line: illumination by 660 nm, red line: difference spectrum. Absorption maxima wavelengths are marked. Dashed horizontal lines mark zero absorption, vertical dashed lines mark the 700 nm wavelength. (a) CBD wild type, (b) PCM wild type, (c) CBD T289H mutant, (d) PCM T289H mutant.