Figure 2. Comparative mapping of actin... | Rockefeller University Press

Figure 2.

$Figure 2. Comparative mapping of actin velocity and substrate stress and computation of the adhesion strength parameter. (A–C) Actin velocity map (A) minus substrate velocity map (B) gives the map of actin velocity with respect to the substrate (C). (D and E) A substrate deformation map (D) was used to calculate the stress map (E). (A–E) Arrows indicate the direction and relative magnitude of velocity (A–C), deformation (D), and traction stress (E). (F) Map of actin velocity–stress alignment and cosine of the angle between F-actin velocity and stress vectors. (G) A map of adhesion strength was computed as a ratio of the stress map and the map of actin velocity with respect to the substrate. The contour within the cell corresponds to the region of the opposite alignment of actin velocity and stress, which is shown in blue in F. (H) The analysis of adhesion strength dynamics in a cell that changed direction of motion showed a drop in adhesion strength upon detachment at one side of the cell (at 20 s) and its subsequent recovery (Video 2). (A–H) The cell margin is shown with the white outline. (I) Coupling in 120-µm2 areas (approximately one quarter of the cell) at the two sides of the cell shown in H was quantified as a fraction of the area in which coupling exceeded 1 kPa s/µm. Resulting values for the left and right sides and their ratio (left to right) are plotted (left, right, and ratio are measured in nondimensional units on the left scale) versus time along with the cell turn angle (direction change is measured in degrees on the right scale). Cell turn angle was measured as the difference between the orientations of the cell’s long axis (determined by approximating the cell with an ellipse) in each pair of the sequential frames. Time is indicated in the images. Bars, 10 µm.$

Comparative mapping of actin velocity and substrate stress and computation of the adhesion strength parameter. (A–C) Actin velocity map (A) minus substrate velocity map (B) gives the map of actin velocity with respect to the substrate (C). (D and E) A substrate deformation map (D) was used to calculate the stress map (E). (A–E) Arrows indicate the direction and relative magnitude of velocity (A–C), deformation (D), and traction stress (E). (F) Map of actin velocity–stress alignment and cosine of the angle between F-actin velocity and stress vectors. (G) A map of adhesion strength was computed as a ratio of the stress map and the map of actin velocity with respect to the substrate. The contour within the cell corresponds to the region of the opposite alignment of actin velocity and stress, which is shown in blue in F. (H) The analysis of adhesion strength dynamics in a cell that changed direction of motion showed a drop in adhesion strength upon detachment at one side of the cell (at 20 s) and its subsequent recovery (Video 2). (A–H) The cell margin is shown with the white outline. (I) Coupling in 120-µm² areas (approximately one quarter of the cell) at the two sides of the cell shown in H was quantified as a fraction of the area in which coupling exceeded 1 kPa s/µm. Resulting values for the left and right sides and their ratio (left to right) are plotted (left, right, and ratio are measured in nondimensional units on the left scale) versus time along with the cell turn angle (direction change is measured in degrees on the right scale). Cell turn angle was measured as the difference between the orientations of the cell’s long axis (determined by approximating the cell with an ellipse) in each pair of the sequential frames. Time is indicated in the images. Bars, 10 µm.