Fig. 2.

Linear progression of gain_fi as opposed to irregular progression of loss_fi.(A) TIRF image of an actin network. The framed areas are analyzed in B–D at an acquisition rate of 20 Hz. (Scale bar: 5 μm.) (B) gain_fi within the left frame of A. The loose network in this region facilitates the separation of a single element from its texture. (Upper) Consecutive TIRF images. The arrow in the leftmost panel indicates the direction of tip progression. (Lower) Difference images color-coded for gain_fi (red) and loss_fi (green). Frames separated by 150 msec were subtracted from each other to make the tip region clearly visible. The double arrow indicates tip advancement within the first 150 msec. Maximum projection (max 0–200 msec) of the difference images results in a red stretch ≈1 μm in length. (C) Line-scan profiles of the advancing tip region at intervals of 50 msec, as shown in red in B Lower.(D) loss_fi within the right frame of A, where the loss predominates gain. (Upper) Sequence of TIRF images. (Lower) Frames separated by 750 msec were subtracted from each other to make the decay of fluorescence intensity visible. Difference images are color-coded for loss_fi (green) and gain_fi (red). The maximum projection (max 0–1,000 msec) of the difference images is shown at far right. (Scale bars in B and D:1 μm.)