I am trying to open PDB (multi subunit complex) from phenix refinement in ChimeraX. One of the chains is A7. While the PDB’s open normally in coot, ChimeraX recognizes a couple of chains as nonstandard residues and is showing XXXX for the entire length of the amino acid sequence (ALA as ALAA 7 , MET as META 7) and so on. The residues correspond to subunit with chain ID A4.

Attached is the sequence view

Please suggest how to fix this.

Thanks

Abhilash.