FIGURE 11.

Microstate helix-coil kinetics. The time evolution of mole fractions calculated over each 1 ns window before reaching equilibrium are shown for the eight dominant clusters listed in Table 4 for the folding (top) and unfolding (bottom) F_s ensembles in AMBER-99φ. From the initially increasing species in each plot, the apparent bulk unfolding mechanism is not equivalent to the reverse of the folding mechanism: folding initiates via nucleation and propagation of small single-helix structures (red) followed by evolution to the diverse equilibrium populations described in the text; in contrast, unfolding begins predominantly with the breaking of single-helix segments into multiple shorter helices (green), and may be considered as nucleation and propagation of the coil state within helical regions.