Sampling the complex energy landscape of a simple β-hairpin

The folding trajectories of a 16-residue β-hairpin are studied using the activation–relaxation technique with a generic energy model. From more than 70 trajectories, three folding pathways emerge. All involve a simultaneous optimization of the complete hydrophobic and hydrogen bonding interactions. The first two follow closely those observed by previous theoretical studies, while the third can be described as a reptation move of one strand of the β-sheet with respect to the other. This reptation move indicates that non-native interactions can play a dominant role in the folding of secondary structures.