Thermodynamics of proteins: Fast folders and sharp transitions

Several small globular proteins exhibit a simple two-state folding process (sharp transition). The rather short folding times of proteins (fast folders) indicate that folding is guided through some sequence of contact bindings. We discuss the possibility for reconciling a two-state folding event with a sequential folding process, i.e. a folding pathway in a schematic model of protein folding. We show that both single and multiple folding pathways can lead to an apparent two-state folding from a thermodynamic point of view. We also discuss water interactions in protein folding, leading to cold and warm destabilization of the protein. (C) 2002 Published by Elsevier Science B.V.