Fig. 1: Structure and morphology of phase separation.

a, A schematic model depicting the structural transition of nucleosomes, from a 10-nm “beads-on-a-chain” structure or loosely-packed polymer state to a fiber-like structure, spinodal condensate, and finally to a spherical condensate through the process of intra-array compaction, inter-array interaction and liquid-droplet formation. b, NS-EM images of the morphology of tetranucleosome incubated with 150 mM, 50 mM and 5 mM Na⁺, respectively, under room temperature for up to 10 h. The spinodal condensate particles are marked by orange circles, while the spherical condensates are indicated by cyan arrows. The boundary for generating spinodal condensate is depicted by orange dash line, while the boundary to generating the spherical condensate is described by cyan dash line. In this experiment, one grid was prepared for each condition, with ~5-10 grid squares examined and imaged, all showing a similar distribution of particles. c, Three representative area of cryo-ET 3D reconstruction of spherical condensate generated from tetranuclesome in physiological salt concentration as described¹⁹. Each 3D map showed by its central slice (top left) and zoomed-in portion of the small spherical condensates (top right), which is compared to the 3D density map superimposed with models (the NCP portions are colored by cyan, and DNA linker portions are colored by yellow).