Fig. 2

Single molecules diffusing within plasma membrane. (A–C) show the pattern of xyz trajectories projected onto the x,y-plane (left) and mobility heat maps (right) for rounded cell shapes and (D) shows the results in a rectangular cell of the same dimensions. Simulation time steps were _Δt = 0.1 ms, 1 ms, and 10 ms as shown and the diffusion coefficient, D, was 0.1 µm²⋅s⁻¹ in all simulations. (E) MSD vs dT plot (± SEM) for trajectories shown in panels (A–D), where dT is the time interval between measurements³⁶. Averaged MSD was calculated using real x,y,z coordinates of each single molecule grey line—small, rounded cell (radius = 0.5 µm, simulation step time, Δt = 0.1 ms, not shown). Inset – the slope of the initial part of MSD vs dT plot (up to 1 dT = 1 s) was used to calculate mobility values (See Table 1). (F) as (E), but instead of using known x,y,z coordinates, the mock movies were tracked using custom video tracking software (see main text) and the x,y-trajectories were used to build the MSD vs dT plots (See Table 1).