Fig. 3.

Flow-induced loop-to-β-hairpin transition of isolated β-switch. Snapshots of simulated structures of WT (A), M239V (B), and A238V (C) β-switches in representative FMD simulations taken at consecutive times (indicated) when the next new H-bond was formed. The simulations started from the loop conformations (1QYY or modeled after 1QYY by mutating residue 239 or 238 to a valine) and ended 6 ns after the first five H-bonds were formed and the loop almost became a complete β-hairpin. Formation frequencies (running fraction of time during which distance between each H-bond donor/acceptor pair was below the 3.5-Å cutoff) for the indicated H-bonds are averaged over six simulations and plotted vs. time for WT (D), M239V (E), and A238V (F). Some of the curves are obscure because they are too close to the x-axis. The end results at 6 ns are shown in G as a bar graph (mean ± SEM of six simulations) for WT (open bars), M239V (hatched bars), and A238V (solid bars). (H) Time required for each H-bond to form and survive for >50 ps the first time (mean ± SEM of six simulations) for WT (open bars), M239V (hatched bars), and A238V (solid bars).