Absorption spectra of various SaBphP1 PCM constructs where the Pr to Pfr transition is initiated with 700 nm light. Black solid line, 20 min of 740 nm; dashed line, 20 min of 700 nm illumination; except (d) where illumination is for an hour. The location of the residues can best be identified in, and their function inferred from Figs. 6 and 9. (a) wild-type, (b) T289H mutant, (c) D208T, T289H double mutant, (d) Y262F, T289H double mutant. Black solid line, dark adapted and 1 h of 700 nm illumination is identical; dashed line, 1 h of 750 nm illumination, (e) R472A mutant, (f) S747A mutant.