Multi-self-overlap ensemble for protein folding: Ground state search and thermodynamics

Long chains of the HP lattice protein model are studied by the multi-self-o verlap ensemble Monte Carlo method, which was developed recently by Iba, Ch ikenji, and Kikuchi. This method successfully finds the lowest energy state s reported before for sequences of the chain length N = 42-100 in two and t hree dimensions. Moreover, the method realizes the lowest energy state that was ever found in a case of N = 100. Finite-temperature properties of thes e sequences are also investigated by this method. Two successive transition s are observed between the native and random coil states. Thermodynamic ana lysis suggests that the ground state degeneracy is relevant to the order of the transitions.