Figure 2.

A) Net charge density calculated from sequence for each dataset IDP. B) Chain-averaged PP_II propensity calculated from sequence for each dataset IDP using experimental propensities.⁷⁹ In A and B, bold lines are dataset averages, whereas grey lines are averages ± the standard deviation. C) R_h (in Å) and K_D for the IDPs identified in panels A and B and the folded proteins chicken egg albumin, bovine erythrocyte carbonic anhydrase, Staphylococcal nuclease, and horse heart myoglobin. Open squares are DLS-measured R_h, from largest to smallest, for the IDPs PGR (38.4 ± 0.9Å), prothymosin-α (33.8 ± 1.3Å), p53(1-93) (32.8 ± 1.2Å), Hdm2-ABD (31.0 ± 0.5Å), ALA⁻PRO⁻ p53(1-93) (27.7 ± 0.9Å), and PRO⁻ p53(1-93) (27.5 ± 1.3Å). Filled circles are R_h estimated as one-half the maximum C_α-C_α distance in the crystallographic structures of albumin,⁸¹ carbonic anhydrase,⁸² nuclease,⁸³ and myoglobin.⁸⁴ K_D is the distribution coefficient determined by SEC. Standard deviations from measuring K_D were < 0.007. The dashed line is a linear fit of R_h to K_D applied to the filled circles (folded proteins), which was used to estimate R_h from K_D for the IDPs. Table S1 lists the averages of the DLS-measured and K_D-estimated R_h for each of the 6 IDPs. Inset: Filled circles are R_h measured by DLS for the folded proteins compared to R_h estimated from crystal structures as one-half the maximum C_α-C_α distance, showing good agreement. DLS-measured R_h for each folded protein was: albumin (35.6 ± 0.5Å), carbonic anhydrase (26.8 ± 0.8Å), myoglobin (22.7 ± 0.8Å), and nuclease (22.4 ± 0.4Å).