Hypothesizing a down event as αLβ2 bending. The animated video (produced by Flash [Adobe]; 24 fps) on the left depicts a BFP position-clamp experiment: an αLβ2-expressing target cell is driven to contact the ICAM-1–coated BFP probe bead, allow formation of an αLβ2–ICAM-1 bond, retract to a desired distance, and clamp at that position for observation of putative αLβ2 conformational changes and ICAM-1 dissociation. The data on the right are the same as those in Fig. 1 H but synchronized with the video. The abrupt displacement down event is hypothesized as integrin bending, as illustrated in the video.
