Fig. 2. MeV droplets exhibit liquid-like behavior.

(A) Turbidity-based phase diagram as a function of P₅₀N₅₂₅ and P_304–507 concentrations. Green shading represents ranges of combinations of protein concentration that form droplets. Examples of fluorescent images at several N and P concentrations that show phase separation are presented around the phase diagram. (B) Fusion events followed by relaxation into spherical droplets in a mixture comprising P_304–507 (100 μM) and P₅₀N₅₂₅ (10 μM). (C) Images of FRAP shows exchange of P₅₀N₅₂₅–fluorescein amidite between phases. (D) FRAP kinetics of P₅₀N₅₂₅ (25 μM with 10 nM P₅₀N₅₂₅-fluorescein) in droplets formed with P_304–507 at 1:2 ratio. (E) FRAP kinetics of P_304–507 (50 μM with 50 nM P_304–507-fluorescein) in droplets formed with P₅₀N₅₂₅ at 2:1 ratio. (F and G) Fluorescence anisotropy of P₅₀N₅₂₅-fluorescein (10 μM P₅₀N₅₂₅, 500 nM P₅₀N₅₂₅-fluorescein) in the dilute phase (black) and in the presence of P_304–507 under phase-separating conditions [N:P = 1:2 (dark green) and N:P = 1:4 (light green)]. Fluorescence lifetimes were measured at room temperature, (F) in buffer containing 150 mM NaCl and (G) in buffer containing 500 mM NaCl that suppresses phase separation but not the interaction between proteins. (H and I) Fluorescence anisotropy of P_304–507-fluorescein (10 μM, 500 nM P_304–507-fluorescein) in the dilute phase (black) and in the presence of P₅₀N₅₂₅ at phase-separating conditions [P:N = 4:1 (dark green) and P:N 2:1 (light green)]. Fluorescence lifetimes were measured at room temperature, (H) in buffer containing 150 mM NaCl and (I) in buffer containing 500 mM NaCl that suppresses phase separation but not the interaction between proteins.