Fig 7.

Summary of the folding kinetics. The observed folding pathways, with their branching ratios, are illustrated. The ratios for the mutant are indicated in parentheses. For each structure, the native-like features are circled or boxed in green. Just before entering two of the three pathways (i.e., the helix-hairpin 1 and helix-hairpin 2 pathways), the helix forms as a result of stabilization by contacts with the β1 or β2 strand (labeled “helix-β1 or -β2”). As expected from its marginal stability (see Simulation Method), helix formation is initiated only when it makes contacts with the strands. After formation of the intermediate, all three pathways converge to a common rate-limiting step, which is the formation of the specific nucleus. Structures exhibiting native-like W43 burial are enclosed in a dotted orange box.