  We have studied the effects of an external sinusoidal force in protein
folding kinetics. The externally applied force field acts on the each amino
acid residues of polypeptide chains. Our simulation results show that mean
protein folding time first increases with driving frequency and then decreases
passing through a maximum. With further increase of the driving frequency the
mean folding time starts increasing as the noise-induced hoping event (from the
denatured state to the native state) begins to experience many oscillations
over the mean barrier crossing time period. Thus unlike one-dimensional barrier
crossing problems, the external oscillating force field induces both
\emph{stabilization or destabilization of the denatured state} of a protein. We
have also studied the parametric dependence of the folding dynamics on
temperature, viscosity, non-Markovian character of bath in presence of the
external field.
