[phenixbb] refinement for ligands with alternative conformation

Hello, I am working on the refinement of a structure about 2.8A, which the substrate ligand has an odd conformation. A blob of negative difference density about 4.8 sigma between the one portion of the ligand and the other. If I break down the ligand into two parts, the negative density disappears, however, one part of the ligands does not fit well. We suspect a mixture of conformations. Any suggestions would be appreciated on how to setup refinement for ligands with alternative conformation. Many thanks, Yi Zheng Department of Biochemistry Michigan State University