Figure 5.

Alternate scenarios of SynGAP/PSD-95 phase separation with auxiliary interactions beyond those underpinning the assembly of stoichiometric S₃P₂ in dilute solution. The schematic representations of S₃ and P here are the same as those in Fig. 2a. (a) Favorable LLPS-driving interactions are envisioned to be restricted to those between S₃ and P (red dashed lines) as modeled by the χ_SP term in Eq. 27 for a simple FH model. (b) LLPS is envisioned to be driven also by favorable interactions among S₃ (blue dashed lines) and among P (green dashed lines) as modeled by the χ_SS and χ_PP terms in Eq. 28a. The bias afforded by this model toward formation of S₃P₂ complexes in the dilute phase is not exhibited in this schematic depiction of the condensed phase. (c–e) Mean-field FH theory predictions for SynGAP/PSD-95 phase behaviors in the alternate scenario in (a) (c and d) and the alternate scenario in (b) (e). The black solid lines with slopes = 1/2 and −1, the dashed tie lines, and the light blue phase boundaries in the three phase diagrams carry the same meanings as those in Fig. 2c. The FH parameters are (c) χ_SP = 10.0 in Eq. 27; (d) ${\mathcal{K}}^0$ = 10⁻¹⁰, χ_SP = 10.0, and χ_SS = χ_PP = 0 in (28a), (28b); and (e) ${\mathcal{K}}^0$ = 10⁻¹⁰, χ_SP = 4.0, and χ_SS = χ_PP = 3.5 in (28a), (28b).