Deterministic Mechanical Model of T-Killer Cell Polarization Reproduces the Wandering of Aim between Simultaneously Engaged Targets
Figure 5
Typical trajectories of centrosomes oscillating within a synaptic area.
(A) A centrosome trajectory in projection onto the synaptic area, with color denoting the height above it and arrows, the direction. The directions of axes are as indicated in Figure 4. Pulling force density, 40 pN/µm; microtubule length, 16 µm; effective cytoplasm viscosity, 2 pN s/µm2. (B) Positions of the centrosome along the two horizontal axes and its vertical position plotted vs. time. Note the phase shift between the oscillations along the x and y axes that leads to gyrations visible in (A), and apparent beats. Pulling force density, 40 pN/µm; microtubule length, 16 µm; effective cytoplasm viscosity, 2 pN s/µm2. (C) Effect of microtubule dynamic instability and of an annular shape of the pulling surface on the pattern of oscillations. Position of the centrosome is plotted vs. time as predicted by the purely deterministic model with the disk-shaped pulling surface, as analyzed throughout the paper (black curve), and with stochastic microtubule dynamic instability and annular pulling surface (colored curves). The two stochastic simulations are independent in the sense of pseudo-random number generation on a computer. The stochastic predictions differ between runs but preserve the characteristic features of the deterministic one. Pulling force density, 20 pN/µm in the deterministic simulation and 36 pN/µm in the stochastic simulations. Microtubule length (starting microtubule length in stochastic simulations) was 16 µm, effective cytoplasm viscosity, 2 pN s/µm2.