  The multicanonical 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.
