Fig. 4.

Free-energy landscapes of segments B, C, and AB at 300 K. For C, it is necessary to distinguish between two possible topologies of the β-hairpin, which may have similar values for the backbone rmsd. We therefore use the rmsd over all nonhydrogen atoms as one coordinate for the free-energy map. For AB, because the observed structure involves a significant nonnative component, we use the α-helix content and energy as the two coordinates. Note that for the β-hairpin, the observed global free-energy minimum does not coincide with the global minimum of energy. The contour lines are separated by 1 kbT.