split into chains loses chain info

[Elaine Meng]

If I open a structure and show the sequence of a chain it includes the missing segment box. If I split (into chains, default) and then show the sequence of that chain it omits the missing segment and concatenates the ends of it together. Screenshot where upper sequence is chain /b after 1t2p split, lower sequence chain /b in another copy of 1t2p that was not split.

The split one also loses the chain name information that appears in the status line on mouseover. Tested in daily build UCSF ChimeraX version: 1.3.dev202110150902 (2021-10-15)

[Tom Goddard]

The split command only copies the atoms and residues. It does not copy metadata such as the sequence which includes missing residues. I don't know if the sequence can be copied with the current atomic model data structures. Eric can advise on that and perhaps enhance the split command code to copy the sequence info.

[pett]

It doesn't depend on the metadata. It depends on copying the Chain information.

[pett]

If 'split' only split by chains, I would undertake this. But it can split on a wide variety of criteria: chains, ligands, connected polymers, etc. So reassigning to Tom. Anyway, to preserve Chain information, you need to use bulk_set on the new chain, like so: new_chain.bulk_set(old_chain.residues, old_chain.characters).

--Eric