  Using Langevin dynamics simulations, we study the hysteresis in unzipping of
longer double stranded DNA chains whose ends are subjected to a time dependent
periodic force with frequency $\omega$ and amplitude $G$ keeping the other end
fixed. We find that the area of the hysteresis loop, $A_{loop}$, scales as
$1/\omega$ at higher frequencies, whereas it scales as
$(G-G_c)^{\alpha}\omega^{\beta}$ with exponents $\alpha=1$ and $\beta=1.25$ in
the low frequency regime. These values are same as the exponents obtained in
Monte Carlo simulation studies of a directed self avoiding walk model of a
homopolymer DNA [R. Kapri, Phys. Rev. E 90, 062719 (2014)], and the block
copolymer DNA [R. K. Yadav and R. Kapri, Phys. Rev. E 103, 012413 (2021)] on a
square lattice, and differs from the values reported earlier using Langevin
dynamics simulation studies on a much shorter DNA hairpins.
