Figure 2.

(a) Absorption spectra of V49A/S169R1/S226R1 without (gray) and during (black) illumination in pH 6.0 buffer (10 mM Pi/Na, 100 mM NaCl, 15% (w/w) glycerol). The decreased absorption in the photostationary state indicates accumulation of the N state. (b) The characteristic N − BR spectrum (gray) obtained by subtracting black spectra from gray spectra in panel a. This difference spectrum was fitted with a standard N − BR spectrum (black) (26) to calculate occupancy of the N intermediate. The black arrow shows 635 nm light from the laser scattered by the membranes.