Dear phenixbb, I'm trying to constrain a ligand-metal bond that is continuously getting altered by phenix.refine (my data's only 3.2A). I've added the following restraint but it just doesn't seem to be holding the bond length during refinement. Is there a different way of telling phenix.refine not to alter this distance? (I'm doing it all on the command line & by editing the .def file). refinement.geometry_restraints.edits { bond { action = *add atom_selection_1 = name CA and chain X and resname CA and resseq 1 atom_selection_2 = name O1 and chain L and resname ROC and resseq 1 distance_ideal = 2.380000 sigma = 0.100 } } Thanks, Simon --------------------------------------------------------------- Dr Simon Kolstoe Laboratory for Protein Crystallography Centre for Amyloidosis & Acute Phase Proteins UCL Medical School Rowland Hill Street, London NW3 2PF Tel: 020 7433 2765 http://www.ucl.ac.uk/~rmhasek ---------------------------------------------------------------