I am struggling with a ligand bound structure. The ligand seems to induce a small conformational change of one loop. However, despite my efforts I did not get any data with a full occupancy for this ligand yet. As a result, I have to deal with a loop in apo state (where ligand occupancy = 0) and a loop with a bound ligand (where ligand occupancy <1) and where the ligand is clashing with the modelled loop in the apo state. Hope I did myself clear. How to deal with this situation ? I am sure that phenix.refine can do it but how ? What I would like to try is something like that "alternate loop A" occupancy = X and "alternate loop B" occupancy = ligand occupancy = 1-X Maybe something specific in a parameter file ? Thank you for your help Xavier