Modeling two-state cooperativity in protein folding - art. no. 041907

A protein model with the pairwise interaction energies varying as the local environment changes, i.e., including some kind of collective effect betwee n the contacts, is proposed. Lattice Monte Carlo simulations on the thermod ynamical characteristics and free energy profile show a well-defined two-st ate behavior and cooperativity of folding for such a model. As a comparison , related simulations for the usual G (o) over bar model, where the interac tion energies are independent of the local conformation, are also made. Our results indicate that the evolution of interactions during the folding pro cess plays an important role in the two-state cooperativity in protein fold ing.