I am trying to refine a structure with modified cysteines, which refmac recognized as CME just fine. Phenix has CME listed in the mon_lib_list.cif, but the CME.cif file was not in the mon_lib/c/ directory. I added it to the phenix mon_lib/c directory but phenix.refine still complained. I next added the CME.cif file ( copied from ccp4) as a command line input to phenix.refine, and added this to my parameters file: refinement.pdb_interpretation.apply_cif_modification { data_mod = CME residue_selection = chain A and resid 381 residue_selection = chain B and resid 381 residue selection = chain B and resid 530 } Still no luck. Thanks for your help, Kendall -- Kendall W. Nettles, PhD Associate Professor Department of Cancer Biology The Scripps Research Institute 130 Scripps Way Jupiter Fl 33458