/To further investigate the effects of PEG on phase separation, we used FRAP on the droplets pre-formed with HP1α-KCK-Atto488 and DNA in the presence of 10% PEG·8000. In the presence of PEG·8000, only ~56% of the bleached fluorescence recovered over the timescale of the experiment in contrast to ~99% recovery observed in the absence of PEG·8000. FRAP experiments on droplets formed with HP1α-KCK-Atto488 alone in the presence of PEG·8000 showed an even smaller fraction of fluorescence recovery. These results suggest that 10% PEG·8000 substantially changes the dynamics of the HP1α proteins within the phase-separated droplet.