Hi Alessio,
You can hide any atoms that you want.  Those backbone atoms are shown because you showed the atoms of the whole residue, and "cartoon suppress false" means to allow showing backbone atoms at the same time as cartoon.  You can either just hide those atoms, or if you don't want to see any backbone atoms at the same time as ribbon, do not use "suppress false" with "cartoon".  There is no reason to use that option unless you want to show some backbone atoms at the same time as cartoon.

Even with "suppress false", however, you can just hide any/all of the atoms.  If you showed the whole residue :35 in chain A, for example, that will include backbone atoms N and C and O.  You can hide them with command:

hide /A:35@N,C,O

Or, if you don't want to figure out the residue numbers, you can Ctrl-click on the atoms to select them (selecting shows green outline) and use menu Actions... Atoms/Bonds... Hide.
<https://rbvi.ucsf.edu/chimerax/docs/user/selection.html>
<https://rbvi.ucsf.edu/chimerax/docs/user/menu.html#actions>

See explanation of the cartoon "suppress" option (suppressBackboneDisplay):
<https://rbvi.ucsf.edu/chimerax/docs/user/commands/cartoon.html>

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


> On Aug 28, 2024, at 12:22 AM, Alessio Nocentini via ChimeraX-users <chimerax-users@cgl.ucsf.edu> wrote:
>
> Thanks a lot Elaine.
>
> I propose you an example. Here is the figure. When typing "cartoon suppress false" I got these segments in red: how can I unshow them?
> How can I show the backbone for some residues only? In fact, I do not want to show backbones of residues such as those in green.
>
> Thank you again
>
> Best
>
> Alessio
>
> <Example.jpg>