Effects on the difference-map (solid circles) and direct-map (open circles) correlations by varying the occupancy of the ligand. For each of the given structures the occupancy of the selected ligand was varied from 0.0 to 1.0 in steps of 0.05. The resulting model was refined with REFMAC for 30 steps. The REFMAC output model was tested for ligand–map correlations. The difference-map correlation can be brought down to expected levels (about 0) by decreasing the occupancy of the ligand. These structures were selected on the basis of having a combination of high-resolution data and (for the deposited structure) an unusual correlation of the ligand density and the difference map.