I have been performing a steered MD simulation on a ligand unbinding from a DNA. I have read through several publications and have come up only few which follows a similar scope. I have analyzed the trajectories and plot a PMF curve at a pulling velocity of 10 A/ns which seem to sample and give a good estimation of the forces. But unfortunately since my ligand is highly positively charged (+4) the PMF curve would keep on rising due to Coulombic forces. I appreciate your valuable expertise into handling this kind of a problem to obtain the correct PMF curve.