Figure 4.

Ligand-free conformational dynamics of FeuA. (A and B) Fluorescence trajectories of surface-immobilized FeuA in the absence of ligand are shown. The top panel shows apparent FRET efficiency (blue), which was derived from the donor (green) and acceptor (red) photon count rates shown in the bottom panel. The number of analyzed molecules is provided in Table S3. (C) A histogram of the lifetime of the ligand-free closed state is shown. The cartoon depicts the ligand-free open and closed states with their estimated lifetimes. To see this figure in color, go online.