  DNA hairpin molecules with periodic base sequences can be expected to exhibit
a regular coarse-grained free energy landscape (FEL) as function of the number
of open base pairs and applied mechanical force. Using a commonly employed
model, we first analyse for which types of sequences a particularly simple
landscape structure is predicted, where forward and backward energy barriers
between partly unfolded states are decreasing linearly with force. Stochastic
unfolding trajectories for such molecules with simple FEL are subsequently
generated by kinetic Monte Carlo simulations. Introducing probabilities that
can be sampled from these trajectories, it is shown how the parameters
characterising the FEL can be estimated. Already 300 trajectories, as typically
generated in experiments, provide faithful results for the FEL parameters.
