Figure 2.

Linear actin filaments maintain canonical F-actin structure. (A and B) Confocal fluorescence (left and middle) and DIC (right) micrographs are given of polypeptide coacervates containing TMR-actin (green) after the addition of Alexa-647-Phalloidin (purple) on nonadherent substrates. (A and B) Focal plane is at the interface of the coacervates and the substrate (surface (A)) or near the midplane of the largest droplet in the field of view (B). Scale bars, 5 μm. Conditions are 0.5 μM Mg-ATP-actin (47% TMR-labeled) incubated with 5 mM pLK before addition of 5 mM pRE in 50 mM KCl, 1 mM MgCl₂, 1 mM EGTA, 10 mM imidazole (pH 7.0), and 72 μM ATP (all concentrations final). 0.25 μM Alexa-647-Phalloidin was flown into the chamber in the same buffer after droplets had sedimented. (C and D) False-colored fluorescence images are given of the regions outlined in yellow boxes in (A) and (B) from the surface (C) and midplane (D). Right column shows a merge. Scale bars, 2 μm. (E) Correlation between normalized TMR-actin and 647-phalloidin fluorescence intensity values is shown for all coacervate-positive pixels in (A). Colors represent count density. Pearson’s correlation coefficient is r = 0.864. To see this figure in color, go online.