The thermal denaturation of Peyrard-Bishop model with an external   potential
  The impact of various types of external potentials to the Peyrard-Bishop DNA denaturation is investigated through statistical mechanics approach. The partition function is obtained using transfer integral method, and further the stretching of hydrogen bond is calculated using time independent perturbation method. It is shown that all types of external potentials accelerate the denaturation processes at lower temperature. In particular, it is argued that the Gaussian potential with infinitesimal width reproduces a constant force at one end of DNA sequence as already done in some previous works. 
A. Sulaiman, F. P. Zen, H. Alatas, L. T. Handoko
physics.bio-ph cond-mat.stat-mech q-bio.BM