Fig. 3.

Absorption spectra of OCP in solution and single crystals. (A) Time-resolved absorption spectra of OCP–ECN solution under flooded white light illumination during a 90-s recording are plotted from red to blue in equal time interval. Fresh protein solution at the concentration of 3 mg/mL and the reference buffer (clear drop) are loaded into a device (Inset). (B) The single-crystal OCP–ECN shows no detectable light-induced spectral change. (C) Time-resolved absorption spectra of the Y201F mutant in solution during a 60-s recording under filtered white light (shortpass filter <600 nm), plotted in equal time interval from red to blue (Inset: difference absorbance with respect to the first curve). (D) Time-resolved absorption spectra of the W288F mutant. Two small shoulders marked by the orange arrows suggest a small fraction of the orange state undergoing photoconversion (Inset).