I have used blind docking (as binding site is not clear) approach to my target protein and finally I have clustered the poses. We have a ligand bind to 3 probable binding sites and have already performed the 3 simulations of of each protein ligand complex (separate binding sites). Now I want to see the cumulative effect of ligand when it binds to all the 3 sites. My question is how do you perform this simulation in gromacs 4.5 protein with all 3 ligands attached to the protein. How will I make the topology file, drg.itp, etc. ?