  We propose a new generalized-ensemble algorithm, which we refer to as the
multicanonical-multioverlap algorithm. By utilizing a non-Boltzmann weight
factor, this method realizes a random walk in the multi-dimensional,
energy-overlap space and explores widely in the configurational space including
specific configurations, where the overlap of a configuration with respect to a
reference state is a measure for structural similarity. We apply the
multicanonical-multioverlap molecular dynamics method to a penta peptide,
Met-enkephalin, in vacuum as a test system. We also apply the multicanonical
and multioverlap molecular dynamics methods to this system for the purpose of
comparisons. We see that the multicanonical-multioverlap molecular dynamics
method realizes effective sampling in the configurational space including
specific configurations more than the other two methods. From the results of
the multicanonical-multioverlap molecular dynamics simulation, furthermore, we
obtain a new local-minimum state of the Met-enkephalin system.
