Folks Phenix has the ability to refine two different amino acids (using alt. loc.) in the one place like in 1ejg. You can read more about it here. https://www.phenix-online.org/newsletter/CCN_2015_07.pdf#page=12 This crashes Coot until you add allow_duplicate_sequence_numbers() to $HOME/.coot.py in OSX or the appropriate place on Windows. For Windows, as there is no $HOME, Coot uses .coot.py or .coot-preferences/ directory for configuration - these can be found (added to) the directory in which Coot was installed (e.g. C:\WinCoot). Nigel PS While you're at it, why not add these lines below to automatically load FEM and polder maps. set_auto_read_column_labels("FEM", "PHIFEM", 0) set_auto_read_column_labels("mFo-DFc_polder", "PHImFo-DFc_polder", 1) --- Nigel W. Moriarty Building 33R0349, Molecular Biophysics and Integrated Bioimaging Lawrence Berkeley National Laboratory Berkeley, CA 94720-8235 Phone : 510-486-5709 Email : [email protected] Fax : 510-486-5909 Web : CCI.LBL.gov