Dear all, i have a problem that i block on for quite a while. i need to add a D atom on carbonyl group (enol) as alternate conformation to a main chain protein amide group to refine with phenix.refine. It is not something that the program phenix.reduce can perdeuterate as it is an unusual position. it actually perdeuterates all the rest of the protein successfully. Does anyone have an idea how to proceed? i tried so far to rename the residue and give .cif restraints generated with readyset for the new tautomer. phenix seemed to recognised it but it failed due to the fact it does not recognise the residue as being a residue to link to the other residues and bounds bounce off. A friend told me a cif_link was the problem. Then i tried to apply cif_modification in a parameter file with the corresponding .cif file as explained briefly on: http://www.phenix-online.org/documentation/refinement.htm#anch88 it does not solve the problem. the link between the new tautomer residue and the rest of the residues does not occur in refinement. Thanks for your help in advance. i am getting deseperate. Maxime