  We introduce a variational approximation to the microscopic dynamics of rare
conformational transitions of macromolecules. Within this framework it is
possible to simulate on a small computer cluster reactions as complex as
protein folding, using state of the art all-atom force fields in explicit
solvent. We test this method against molecular dynamics (MD) simulations of the
folding of an alpha- and a beta-protein performed with the same all-atom force
field on the Anton supercomputer. We find that our approach yields results
consistent with those of MD simulations, at a computational cost orders of
magnitude smaller.
