Single particle tracking of S1-Qdot conjugate. (A) Single particle tracking of S1-Qdot conjugate. The diffusion of the S1-Qdot particles on the membrane of Escherichia coli was analyzed at different time points and plotted against time. After addition of peptide to a final concentration to 1 μM, movement of the particles slowed down. (B) Movement trajectories of S1-Qdot-conjugate on E. coli were measured. Time on trajectories correspond to the total time during the particle movement over the bacterium. The conjugate was tracked over its xy-path over 100 frames. The black trajectory corresponds to the peptide movement at low concentrations of S1 (1 × 10-14 M) whereas the red trajectory represents movement at 1 μM S1. Starting points were set to 0/0 (x/y) for both trajectories. (b) Before unlabeled peptide was added fast lateral diffusion can be observed. (c) After addition of peptide the particles show slow lateral diffusion. Data was obtained from seven independent measurements.