Figure S6.

Related to Figure 6

A: Calibration curve of GFP fluorescence as a function of GFP concentration. B: Quantification of GFP-G3BP1 enrichment within G3BP1-RNA condensates, as determined by fluorescence intensity inside/outside condensates. C: Cryo-EM image of G3BP1-RNA droplets deposited post fixation on a holey film EM grid. Arrowheads point to droplets partially deposited in the holes of the film that are amenable for tomographic tilt series acquisition. D: Tomographic slice, 4 nm in thickness, of a G3BP1-RNA droplet. Putative naked RNA molecules are observed outside the droplet. Multiple ‘beads on a string’ are observed inside the droplet and may be interpreted as G3BP1 molecules bound to RNA. The dense beads are 3-4 nm in diameter, and regularly appear in pairs. Occasionally, larger clusters (30-40 nm diameter) of beads are observed. E: Zoom into cluster in D. For the full tomographic volume, see Video S4. F: Additional examples of clustering and pairs of ‘beads on a string’ from a different tomographic slice of the same droplet.