[chimerax-users] not showing non-traced amino acids in sequence view after splitting a molecule

[Elaine Meng]

Hi Marta,
When you open a structure from PDB or mmCIF format, there is a special part of the file that gives the full sequence of the structure used in the experiment, even if parts of that structure are not visible in the density (and therefore do not have atomic coordinates).  This is part of the model information.

However, “split” makes new models, and it currently loses various kinds of information.  I believe this is the case in both Chimera and ChimeraX.  After splitting, it must only look at the coordinates to get the sequence. 

 My personal opinion is to avoid using “split” unless it is really necessary.

In Chimera it sometimes helped with molecular surface calculation, but in ChimeraX there is less reason to do it.  You can specify chains individually without splitting.  The main reason one might split is for separately fitting the chains.  However, if having the full sequence is important, you can instead open multiple copies of the original model and just delete the parts of each that you don’t need.

I hope this helps,
Elaine
-----
Elaine C. Meng, Ph.D.
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Mar 2, 2020, at 8:30 AM, Marta Perez Illana <marta.perez at cnb.csic.es> wrote:
> 
> Hi all
> When I open a cif in chimerax and press the sequence button the window shows up and there is everything within the molecule, including the non-traced amino acids (missing in the structure).
> 
> Whereas if I do split the molecule to have just one chain, then the sequence view only shows traced amino acids, but not the non-traced ones anymore... Any ideas on this please?
> 
> P.D. With cif files this was a bit confusing in regular chimera for me as well, since when saving the cif it was kind of converted and I guess some info regarding this non-traced aminoacids was missed...
> 
> Thank you!!!
> Marta