FIGURE 3.

Typical tether extraction experiment. (A) Time course of a bead dragging by LOT. The motion of the laser tweezers with the trapped bead started at 1.5 s and continued until the bead escaped at 12 s. (Inset) The bead displacement from the center of the trap Δx increased rapidly during the last 2 s, indicating a sudden increase in the tether force. (B) Force exerted on the bead by LOT as a function of the tether length. During tether growth, force fluctuated near 3 pN, suggesting that the membrane was pulled from a reservoir. After reservoir depletion at 7 μm tether length, the force rapidly increased until the bead escaped from the trap.