Global minimum configuration of a small peptide for the ECEPP/2 and ECEPP/3 force fields

We use a multicanonical ansatz to search for low energy conformations of a small peptide, Met-enkephalin. We found that the global minimum conformation of ECEPP/3 differs from that of the ECEPP/2 force field. The distribution and relative weights of the two conformations are calculated for various temperatures and compared for both force fields. We show that at room temperature and for both force fields the conformer which is the ECEPP/2 ground state is favored over the one which is the ECEPP/3 ground state.