Figure 1.

Transport of beads along adherent filopodia initiated and analyzed by optical tweezers. (A) Sketch of the mechanistic model describing the transport process along an adherent filopodium toward the cell body. The transported bead is tracked interferometrically in 3D. (B) Kelvin-Voigt model for the bead interacting with the surrounding fluid (friction (γ_b)), the optical trap (trap stiffness (κ_opt)), and the cellular protrusion (with elements γ_c and κ_c). (C) DIC image series of J774 macrophage transporting a bead along a filopodium toward its cell body. The bead is captured and tracked inside the focused laser beam during the entire retraction process. To see this figure in color, go online.