Fig. 3

Enzymatically catalyzed polyU/spermine coacervate formation inside liposomes. a A schematic showing polyU/spermine coacervation within a liposome. UDP diffuses inside the liposome through α-hemolysin pores and is consumed by the enzyme PNPase to elongate encapsulated cy5-U20 seed oligomers. The formed polyU RNA further interacts with spermine to form polyU/spermine coacervates, which fuse together to form a single condensate over time. b Time-lapse fluorescence images (red: lipid bilayer; green: cy5-U20) showing polyU/spermine coacervation process inside a liposome. Note the simultaneous formation of several coacervates that further coalesce to form one single entity. Compared to pLL/ATP coacervation, the process proceeds slowly, as it is primarily dictated by the RNA elongation process. c Average number of coacervates present within the liposomes as a function of time. A few coacervates (~4) are observed at the start, whereupon the average number decreases to about 1.3 within the next 5 min. d Evolution of the average coacervate size with time. Initially formed small coacervates (~0.6 µm) more than double in their diameter through growth and fusion, to ultimately form a ~1.5 µm coacervate that is freely diffusing inside the liposome. e Coacervate-phase intensity versus time (n = 11 liposomes, obtained from a single experiment). The transition from a homogeneous solution into a condensed coacervate phase leads to a gradual increase in the fluorescence. f Dilute-phase intensity versus time (n = 11). As the coacervates continue to grow, there is a gradual, linear decrease in the fluorescence of the dilute phase. See Methods for details of the analyses involved for panels (c–f). Error bars in (c, d) indicate standard deviations. Dashed vertical lines in (e, f) indicate the onset of coacervation, the plots show the average values, with the shaded regions indicating standard deviations. Source data are provided as a Source Data file