Chain ID peculiarities

[petneb]

This is from PDB 6n2y. I don't get how these disconnected atoms are selected by these nodes:

[BradyAJohnston]

Hi @petneb - those are atoms from the ATP that is in the structure. The Is Backbone selects backbone atoms for both protein and nucleic acids, which includes the ribose of the ATP. The selection is based purely on the atom names and not whether it is part of a longer chain.

If you combine the selection with the Is Peptide it will limit it to just the protein backbone and no longer select those atoms: