Variation of the Energy Landscape of a Small Peptide under a Change from the ECEPP/2 Force Field to ECEPP/3

Themulticanonical ansatz is used to study variations in the energy landscape of a small peptide, Met-enkephalin, under a change from the ECEPP/2 force field to ECEPP/3. Local minima with energies up to 5 kcal/mol higher than the global minima are sampled and classified according to H-bridges and backbone angles. The distribution and relative weight for various temperatures of the minima are calculated and compared for the two force fields. We demonstrate that while there are small differences in the energy landscape our results at relevant temperatures are robust under changes between ECEPP/2 to ECEPP/3. New address: Institute for Molecular Science (IMS), Okazaki 444, Japan