Fig. 9.

Parallel folding pathways of the VPK PK. (A) States of VPK are designated as PK (folded PK), pkHP1 and pkHP2 [partially folded (hairpin) states], and U (unfolded state). In the top pathway, stem 1 folds first to form the pkHP1 hairpin state; in the bottom pathway, stem 2 folds first to form the pkHP2 hairpin state. The structures representing the four states were taken from simulations. (B) Salt dependence of the VPK folding pathways from coarse-grained simulations. The fraction of molecules that fold via the pathway that populates pkHP1 as an intermediate is plotted as a function of the monovalent salt concentrations. The error bars represent the 95% exact confidence intervals. The free-energy difference between the two pathways, calculated based on the fraction of pkHP1, is marked on the right axis.