Hi All, I'm refining a structure (dev-1726) that contains 24 protein subunits which are assigned to chains A-X in the PDB file. Chains Y and Z are assigned to a couple of ligands and the ordered solvent molecules are chain w (lower case). I decided to give the "Update waters" option a try during refinement but it seems that the chain ID of the ordered solvent is changed to chain S by default. Since I already have a protein subunit assigned to chain S, the following error is obtained when I try to open the model in Coot (ERROR 39 READ: Duplicate sequence number and insertion code.). To enable visualization of the model in Coot, I can of course manually change the chain ID for the ordered solvent in the output PDB file using a text editor. However, is there a way to override the ordered solvent default chain ID in Phenix to prevent duplication? Thanks, Scott __________________________________ Scott Lovell Ph.D., Director Protein Structure Laboratory University of Kansas Del Shankel Structural Biology Center