Hi all,

I occasionally use ChimeraX's "build structure" to construct short peptides to use in teaching. For efficiency's sake, it would be nice if I could take things I've already built and "mutate" an amino acid using the swapaa command. However, when I try to do this using a custom built structure (for example, selecting the residue I want to change, and then executing swapaa sel arg), I get the error "No amino acid residues specified for swapping". 

The command works for downloaded structures, just not the custom ones. Is there a missing attribute that swapaa checks for, that isn't created when you make a custom peptide?

Dan