A CRITERION THAT DETERMINES FAST FOLDING OF PROTEINS - A MODEL STUDY

We consider the statistical mechanics of a full set of two-dimensional protein-like heteropolymers, whose thermodynamics is characterized by the coil-to-globular (T-theta) and the folding (T-f) transition tempe ratures. For our model, the typical time scale for reaching the unique native conformation is shown to scale as tau(f) similar to exp[sigma/ sigma(0)]. We argue that T-f scales linearly with the inverse of entro py of low-energy non-native states, whereas T-theta is almost independ ent of it. As sigma-->0, non-productive intermediates decrease, and th e initial rapid collapse of the protein leads to structures resembling the native state. Based solely on thermodynamic information, sigma ca n be used to predict sequences that fold rapidly.