Comment on the paper "Comparison of the measured phase diagrams in the force-temperature plane for the unzipping of two different natural DNA sequences" by C.H. Lee, C. Danilowicz, V.W. Coljee, and M. Prentiss.

The paper by Lee et al. describes the experiments on the unzipping of lambda DNA sequences as a function of force and temperature. This comment aims to stress that the unzipping takes place out of equilibrium due to high sequence-dependent free-energy barriers. The force at which a heterogeneous sequence is unzipped therefore depends on the experimental waiting time.