Hi Yaowang, You can open the 8zza IHM model in ChimeraX using open 8zza from pdbdev If you get tomorrow's ChimeraX 1.10 release candidate or daily build you could also use open 8zza from pdbihm I just added the database name "pdbihm" because pdbdev was the development name of the IHM repository and is being phased out. As Ben said 8zza is a coarse grain model. Although you will see spheres in the model they do not represent individual atoms. The may represent whole residues or large subunits. Tom IHM 8zza shown in ChimeraX: 

On May 13, 2025, at 6:08 PM, Yaowang Li <liyaowang2911@163.com> wrote:

Hi, Ben and Tom

Thank you for your help.

“Real structural model” is not the right expression; I mean an atomic model. There should be an atomic model that was generated from the coarse-grained model, and the molstar program on the IHM website can display its atomic model. So it will be perfect that I can open it in Chimerax for viewing this complex structure. In short, I just want to get the atomic model, not the coarse-grained model.

Best wishes,

Yaowang

From: chimerax-users-bounces+liyaowang2911=163.com@cgl.ucsf.edu <chimerax-users-bounces+liyaowang2911=163.com@cgl.ucsf.edu> On Behalf Of Tom Goddard via ChimeraX-users Sent: Wednesday, May 14, 2025 2:01 AM To: liyaowang2911@163.com Cc: chimerax-users@cgl.ucsf.edu Subject: [chimerax-users] Re: cif file from pdb-ihm, the integrative structure

Hi Yaowang,

As Ben points out 8zza is an integrative hybrid model (IHM). Unfortunately the PDB gives ChimeraX a file with suffix ".cif" for 8zza that does not use the atomic model mmcif dictionary. ChimeraX would need to look at the contents of the file to decide that it is using the IHM dictionary. Currently ChimeraX identifies file types using the file suffix ".cif". That is why it says "No mmCIF models found" when you open this file. I've made a ChimeraX bug report to see if we can improve this

https://www.rbvi.ucsf.edu/trac/ChimeraX/ticket/17661

ChimeraX is able to read the IHM files. So if you download the 8zza.cif file and open it in ChimeraX with "open ~/Downloads/8zza.cif format ihm" it will show you the coarse grain model.

Tom

...

On May 13, 2025, at 8:58 AM, Ben Webb via ChimeraX-users <chimerax-users@cgl.ucsf.edu <mailto:chimerax-users@cgl.ucsf.edu>> wrote:

On 5/13/25 7:33 AM, Yaowang Li via ChimeraX-users wrote:

...

I am trying to analyze the structures that were deposited in the https://pdb-ihm.org <https://pdb-ihm.org/><https://pdb-ihm.org <https://pdb-ihm.org/>> Such as the entry: 8zza [...] which is a coarse-grained model, instead of a real structural model consisting of atom coordinates. Could anyone help me figure it out?

8zza is a model of the yeast nuclear pore complex. As you have observed, it is a coarse-grained model, not atomic. I'm not sure what you mean by "real structural model" but the resolution of the data in 2018 was such that only a coarse-grained structure was possible. That's what was deposited and that's what ChimeraX will show you. What are you trying to do?

Ben -- ben@salilab.org <mailto:ben@salilab.org> https://salilab.org/~ben/ "It is a capital mistake to theorize before one has data." - Sir Arthur Conan Doyle

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