Hi Chimera developers and users, I have faced a problem with chain IDs and secondary structure while working on a large file. As I am refining my model in Phenix and visualizing in Chimera, I need to go back and forth between these two software and that creates a problem. To replicate my problem, here I have taken an example from PDB so that you get the idea. If I take model bearing PDB id 5IRE and apply "phenix.pdb.biomt_reconstruction" I can generate the complete virus icosahedral structure from the asymmetric unit. But when I open this complete virus structure in Chimera and save it back again the chain IDs get changed. Is there any work around to maintain the original chain IDs and therefore maintain the secondary structure definitions in the file header, after opening and thereafter saving using Chimera? Best regards, Tofayel NTU Singapore