Phase diagrams for DNA denaturation under stretching forces

Double-stranded DNA denaturation induced by an external force is modeled as a pair of complementary self-avoiding polymers with inter-strand binding potential. The resulting force-temperature phase diagram is determined using heuristic arguments, exactly solvable models and 3D Monte Carlo simulations. The results are qualitatively different for the cases where the force is applied to only one strand or to both strands. Crucial ingredients for getting a qualitative agreement with experimental results are the persistence lengths and the monomer sizes of single-stranded and double-stranded DNA. The subtle dependence of the small force behavior on the latter parameters, on the stretching mode and on the presence of denaturation bubbles is analyzed in detail.