Efficiency of LIE method

 Dear all,
 I am trying to apply the Linear Interaction Energy method to a set of peptides.
 Unfortunately the method is not very successfull, I have trouble obtaining
 convergence of the Electrostatic potential. I believe this is because a few
 residues are charged. I have the impression that increasing the length of the
 simulation won't help solve the problem. So I'd like to know if there are ways
 to solve this problem within the context of the LIE method or if the method is
 not adapted for simulating charged ligands.
 Julien Michel