Fig. 3. Subunit (dis-)assembly of MinD particles diffusing on membranes.

a, Schematic representation of the time-resolved mass analysis of single MinD trajectories, which reveals attachment (at) and detachment (dt) events along the trajectory as well as a particle’s full membrane release (rl) at the end of its trajectory. b, Representative mass time traces of MinD trajectories (gray line) and corresponding step fits (black line) determined by a step-finding algorithm that locates mass change points within a trajectory. c, Mass step size distribution derived from step fits as depicted in b revealing MinD subunit sizes for at and dt events at particle densities: 0.1 µm⁻², pale blue (n = 20,796 plateaus); 0.3 µm⁻², light blue (n = 26,177 plateaus); 0.6 µm⁻², blue (n = 25,864 plateaus) and 0.8 µm⁻², dark blue (n = 7,506 plateaus). d, Dwell time plots for MinD particles before at events (top plot), representing the lengths of mass plateaus preceding a mass increase and before dt events (bottom plot), representing the lengths of mass plateaus preceding a mass decrease. Dwell times are shown for the MinD dimer (66 kDa) (light blue triangles) and the MinD tetramer state (132 kDa) (dark blue triangles). Plateau numbers for at are dimer, n = 23,782; tetramer, n = 5,088 and for dt are dimer, n = 3,143; tetramer, n = 10,406. Inset shows box plots that indicate second and third quantile (box), median (horizontal line) and 1.5× the interquartile range (whiskers) of bootstrapped mean dwell times (n = 10,000). e, MinD mass distribution for rl events. MinD particle densities: 0.1 µm⁻², pale blue (n = 117,086 plateaus); 0.3 µm⁻², light blue (n = 169,957 plateaus); 0.6 µm⁻², blue (n = 284,916 plateaus) and 0.8 µm⁻², dark blue (n = 120,654 plateaus). f, Plot of the dwell times before rl for the MinD dimer (light blue) and tetramer state (dark blue). Plateau numbers are dimer, n = 562,011; tetramer, n = 73,037. Inset shows box plots, details of which are as described in d.

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