Figure 5. Photoswitching of mKikGR at the single-molecule level.

(A) Fluorescence images of individual red mKikGR molecules embedded in polyacrylamide gel (100 pM, pH 7.0). The images were recorded with 568 nm excitation (130 W cm⁻², 100 ms integration, 1 Hz). The sample was illuminated with 405 nm light (33 mW cm⁻²) between 568 nm pulses. The images were recorded after 0, 1.8, 8.1, and 22 seconds total illumination time with 405 nm light. (B) Time course of integrated intensities of the images. The solid line shows fitting with a first order kinetic model. (C) Excitation power dependence of the photoswitching rates determined from the single-molecule measurements. The solid line shows theoretical switching rate calculated from bulk experiments.