Fig. 3. A protein denaturant modulates the hysteretic phase behavior of LCST IDPPs.

(A) Cloud point temperatures as a function of increasing concentrations of a protein denaturant (urea) in PBS for IDPPs with negligible—(VPGVG)₄₀ and (VPGVG)₈₀; see fig. S5—moderate—(VAPVG)₄₀ and (VAPVG)₈₀—and large—(TPVAVG)₄₀, (TPVAVG)₈₀, (VGPVG)₄₀, and (VGPVG)₈₀—hysteresis. Values were normalized to T_cp in PBS without urea. To overcome the overlapping of normalized T_cp’s, these data are also presented as separate panels in fig. S5. (B) Degree of thermal hysteresis for IDPPs made of VAPVG repeats at a fixed concentration of 50 μM in PBS supplemented with increasing amounts of urea. (C) Temperature-dependent optical turbidity data in PBS + 1 M urea for two IDPPs with identical repeat number but different repeat motifs that encode widely different hysteretic behaviors. Even in 4 M urea, 40-mer IDPPs of TPVAVG repeats display pronounced hysteretic behavior (fig. S5). (D) Phase behavior data as in (C), in PBS with 1 or 2 M urea, but exclusively for (TPVAVG)₈₀ and when the phase transition is triggered without exceeding 45°C during the heating cycle. All relevant T_cp values were calculated from optical turbidity data at a concentration of 50 μM in PBS or PBS supplemented with urea as indicated.