Figure 4

Differences between crosslinking motifs have minimal impact on the steady-state viscosity and filament mobility in actin-microtubule composites. (a) Complex viscosity η(ω) versus frequency ω for different crosslinking motifs displayed in legend. Solid line denotes power-law scaling with exponent shown. (b) For each composite, a 128 × 128 image shows the standard deviation of intensity values for each pixel over time for actin (green) and microtubules (red) in a 60 s time-series. Scale bar is 10 µm and applies to all images. (c) Box-whisker plot of the steady-state mobility, determined by computing the average standard deviation of pixel intensities <δ> normalized by the overall average pixel intensity <I> for each time-series (as described in Methods). For each composite type, <δ>/<I> is calculated separately for actin (cross-hatched) and microtubules (solid) and each data point is computed from 10–12 time-series each collected in different regions of the sample chambers of two different samples. As shown, microtubules are less mobile than actin filaments in all composites. Further, while crosslinking reduces the mobility of both filaments, the specific crosslinking motif has little effect.