[Chimera-users] error: more than 63 chains; cannot uniquely identify with single characters

Elaine Meng meng at cgl.ucsf.edu
Fri Jul 15 09:44:41 PDT 2016

On Jul 15, 2016, at 7:39 AM, Wu, Weimin (NIH/NIAMS) [E] <weimin.wu at nih.gov> wrote:

> Dear Elaine,
> I have a pdb structure with four chains A, B, C, D. and an icoshedral cryo-EM density map. I fit the pdb into the map, and generate 60 copies. I try to merge all these 60 pdbs into a combination, but without renumbering the residues (choose "retain the name" option). I did this operation before without any error, but now it came with the error "more than 63 chains; cannot uniquely identify with single characters". 
> If choose renumber the residues, then the merged is not easy to understand, not easy for comparison either. 
> Is there any other way to do it? Thank you,
> Weimin

On Jul 15, 2016, at 8:43 AM, Wu, Weimin (NIH/NIAMS) [E] <weimin.wu at nih.gov> wrote:

> Or easy to understand, can we add model number into the pdb as done in biological assembly pdb structure 1qgt.pdb1?

Hi Weimin,
I’m not sure how you made the copies, but if they are atomic structures I think this will work: Similar to what you said in your second message, instead of merging into a single model, simply keep all the models separate.  You can still save to a single “multi-model” PDB file with the main menu: File… Save PDB (or just save the Chimera session for later).

Then the copies will still all have chain IDs A,B,C,D which may be easier to work with anyway.  I tried this with 1pov (which has chains 0,1,3) and with “sym” made the whole assembly with 59 more copies for 60 total. I looked in the model panel and they were models #0 (original) and #1.1-59 (copies).  I saved as single PDB file and read it back in, and again had those same 60 models, each with the original chain IDs 0,1,3.

It is recommended you send questions to chimera-users at cgl.ucsf.edu (CC’d here) instead of just me because I am not the expert on everything.  :-)

I hope this helps,
Elaine C. Meng, Ph.D.                       
UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab
Department of Pharmaceutical Chemistry
University of California, San Francisco

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