FIG. 3.

Simple RPA^55,56 salt-free phase diagrams for the four Ddx4 sequences in Fig. 2(a). (a) Phase diagrams computed using the Coulomb potential in Fourier space, U_k = 4πl_B/k², are very similar to the fG-RPA phase diagrams in Fig. 2(c). (b) Phase diagrams computed using a Coulomb potential with a short-range cutoff, U_k = 4πl_B/[k²(1 + (kl)²)]; the same potential used in our previous simple-RPA studies.^24,55–58 This Coulomb potential with a short-range cutoff predicts that the two pH1 sequences have critical temperatures even higher than that of wildtype Ddx4 at pH7. This prediction, however, contradicts the physical intuition that polyelectrolytes should have lower phase separation propensities than neutral or near-neutral polyampholytes of the same chain length.