[Chimera-users] Stuck in adding residue in the C-terminal of a segment

Dear Experts, This is regarding adding an ALA residue in the C-terminal of a specific protein domain, with CHIMERA. I have a protein-complex with multiple domains and chains. I want to add an ALA residue (101-th position) in the chain D, after the 100th residue which is PRO. I followed the tutorial and have given the following command in command line: addaa ala,101 :100.d The following outcome was: Couldn’t find ‘O’ backbone atom of PRO 100.D. Request you to kindly let me know what the possible solution could be, so that I add an ALA residue in the C-terminal of Chain D. Thank you in advance, Regards, Prathit Chatterjee