Directional Transport of a Bead Bound to Lamellipodial Surface Is Driven by Actin Polymerization

Figure 1

(a) Process of the construction of the Hirata chamber. The process after the coating of the coverslip with aminopropyltriethoxysilane is shown. See Section 2.2 for details. (b) The experimental set-up. An optical trap was generated in Zeiss inverted phase-contrast microscope by focusing an infrared laser beam (thick vertical arrow) with an objective lens (NA = 1.3). A poly-D-lysine-coated bead was captured in the trap and was attached to the edge of lamellipodium (the dashed arrow). As soon as the stable contact between the bead and the lamellipodium was achieved, the laser was turned off and the bead was allowed to move on the cell surface (bold horizontal arrow). The phase-contrast image of the bead was acquired with a CCD camera and was recorded on a digital video tape at 30 frames/sec. Video sequences were transferred to a hard disk for the off-line analysis (see Section 2.5). The figure is not drawn to scale.

(a)

(b)