Dynamics of individual QD-labeled BKCa channels in live COS-7 cells. (A) Trajectories of five different QD-labeled AP-rSlo-RFP channels. QD-labeled channels were selected in the central (a–c) and peripheral regions (d and e) of cells. Scale bar, 10 μm. (Lower panel) Magnified view (3×) of individual trajectories. (B) Histogram of mean-squared displacement (MSD) of QD-labeled AP-rSlo-RFP at 15 s. The distribution of MSD values at 15 s is shown for QD-labeled AP-rSlo-RFP channels (open bars, n = 300). As the control, free QDs attached nonspecifically to the coverslip are shown (hatched bar, n = 100). (C) MSD versus time plot of QD-labeled AP-rSlo-RFP. Time-dependent changes in average MSD values are shown for QD-labeled AP-rSlo-RFP channels (open circles) and free QDs (diamonds). The time interval is 300 ms, and error bar represents mean ± SE.