  Molecular simulations of the forced unfolding and refolding of biomolecules
or molecular complexes allow to gain important kinetic, structural and
thermodynamic information about the folding process and the underlying energy
landscape. In force probe molecular dynamics (FPMD) simulations, one pulls one
end of the molecule with a constant velocity in order to induce the relevant
conformational transitions. Since the extended configuration of the system has
to fit into the simulation box together with the solvent such simulations are
very time consuming. Here, we apply a hybrid scheme in which the solute is
treated with atomistic resolution and the solvent molecules far away from the
solute are described in a coarse-grained manner. We use the adaptive resolution
scheme (AdResS) that has very successfully been applied to various examples of
equilibrium simulations. We perform FPMD simulations using AdResS on a well
studied system, a dimer formed from mechanically interlocked calixarene
capsules. The results of the multiscale simulations are compared to all-atom
simulations of the identical system and we observe that the size of the region
in which atomistic resolution is required depends on the pulling velocity, i.e.
the particular non-equilibrium situation. For large pulling velocities a larger
all atom region is required. Our results show that multiscale simulations can
be applied also in the strong non-equilibrium situations that the system
experiences in FPMD simulations.
