Normalized autocorrelation functions for streptavidin diffusing in PBS buffer with and without dextran obstacles (200 g/l of 276.5 kDa dextran). The fit of these autocorrelation functions using the anomalous diffusion model () gives

*α* = 0.99 ± 0.01 for no obstacles, and

*α* = 0.76 ± 0.01 with obstacles (

*solid lines*). The failure of the fit with the simple diffusion model ( with

*α* = 1) for the case with obstacles is also shown (

*dashed line*). The fit with the two-component model () closely resembles the fit with the anomalous diffusion model and is not shown for clarity of the plot. (

*b*) Residuals of the fits of the autocorrelation function in panel

*a* for the case with dextran obstacles with both the anomalous diffusion model (dots,

*χ*^{2} = 0.0024 for 459 data points from

*t* = 0.5

*μ*s to 1 s, with three adjustable parameters) and the two-component model (

*solid line*,

*χ*^{2} = 0.0028 for the same data points with four adjustable parameters) are shown for the timescale relevant to diffusion. At shorter timescales, the two models are practically identical and the scatter in the data is large. (

*c*) Asymptotic long-time behavior of the data and fits to the autocorrelation functions shown in panel

*a*. For the case without dextran obstacles, the fit with the anomalous diffusion model shows a

scaling (

*solid line*). For the case with obstacles, the fit with the anomalous diffusion model shows a

scaling (

*solid line*,

*α* = 0.76), whereas the fit with the two-component model shows a

scaling (

*dashed line*).

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