Figure 10. Radius of gyration (R_g) of the PSI over the time course of the simulations.

R_g of the PSI at pH 4.5 (blue line) and pH 7.4 (orange line) as a function of time. In either case, the PSI was free to move in the extended state. Upon adoption of a saposin-like fold, the collapse of the hydrophobic concave face of the PSI onto itself limits movement, thereby restricting water access to the hydrophobic core.