Fig. 3

DNA linker as programmable surfactant. a RNA transcripts that act as surfactants in the nucleolus [91, 92]. The nested nucleolus comprises immiscible liquid-state condensates: (from the core) a fibrillar center (FC), a dense fibrillar component (DFC), and a granular component (GC). Ribosomal RNA (rRNA) is transcribed at the FC–DFC interface. As nascent rRNA transcripts undergo processing and ribosomal subunit assembly, they are preferentially expelled outside the nucleus. When the transcription machinery is switched off, the tripartite layered organization is disfavored and replaced with a pancake-like conformation. Adapted [92] with permission. Copyright 2021, Nature Publishing Group. b Sequence-specific interaction of DNA droplets [22]. (i) Different liquid condensates of orthogonal DNA Y-motifs (Y_A and Y_B) favor segregation while fusing with those of the same sequence. (ii) Time-sequential snapshots of selective droplet fusion events. c Linker DNA, L_AB, which binds to both Y_A and Y_B. (i) Linker SEs hybridize with motif SEs labeled in the corresponding color. (ii) In the presence of L_AB, the orthogonal DNA motifs favor the formation of mixed-state droplets, which can (iii) fuse with each other. d Cleavage of the linker leads to dynamic phase separation. (i) Chimeric linker, which includes two RNA sequences at the center junctions. Upon the input of ribonuclease A (RNase A), the linker favors cleavage. (ii) In the presence of RNase A, mixed-state droplets favor phase separation into immiscible phases. Adapted [22] under the terms of the Creative Commons CC BY-NC 4.0 license. Copyright 2020, American Association for the Advancement of Science. Scale bars: (b, c) 10 µm; (d) 20 µm. e Molecular input of DNAs (RNAs) functioning as fuel thermodynamically drives linker cleavage. The linker is designed to undergo SDRs upon inputs of targeted sequences. In the free-energy landscape, the fuel lowers the energy barrier (dashed curve in magenta). \(\varDelta G\) is the free-energy gap between the local minima