Figure 4: Mobility of CD59 decreases linearly with increasing mGFP-GPI surface density.

(a) The mean square displacements of CD59 ON (black) and OFF (grey) mGFP-GPI-enriched areas as a function of t_lag for a representative cell. Diffusion coefficients were determined by fitting the function MSD=4Dt_lag+4σ²_xy (bold lines). Only the first two data points were considered for fits. We also included an anomalous diffusion fit with MSD=4Dt_lag^α+4σ²_xy (hairlines), yielding α_ON=0.917 and α_OFF=0.949. The first 10 data points were considered for fits. The inset shows a magnification of the first four data points. Relative diffusion coefficients D_ON/D_OFF of CD59 were determined for 31 individual cells in six independent experiments and plotted as a function of (b) mGFP-GPI density ρ_mGFP-GPI or (c) average mGFP-GPI spacing d_mGFP-GPI. Data were fitted with D_ON/D_OFF=1−d₀²/d_mGFP-GPI² yielding the characteristic nearest-neighbour distance of mGFP-GPI at the percolation threshold d₀=6.3±0.2 nm. The grey circle indicates the data point shown in a. The grey lines represent the s.e. of the fit. (d) Relative diffusion coefficients D_ON/D_OFF of CD59 as a function of average mGFP-GPI spacing d_mGFP-GPI in T24 cells (open diamonds) and in HeLa cells (closed diamonds, N=11, three independent experiments).