ABSTRACT
The complexity of protein folding originates in large part from the huge amount of rotations about single bonds that are possible in a polypeptide chain. Even when only the backbone is considered, rotations about two single bonds can occur at every Cα atom. The enormous number of conformations that are thus possible for the backbone of an unfolded protein have long been considered as a major problem for protein folding (Levinthal, 1968).
