Hybrid-36 LINK records

[Tristan Croll]

The following bug report has been submitted:
Platform:        Linux-3.10.0-1127.19.1.el7.x86_64-x86_64-with-glibc2.14
ChimeraX Version: 1.2.dev202103230345 (2021-03-23 03:45:30 UTC)
Description
Seems that LINKs in hybrid-36 PDB files still aren't being applied correctly by ChimeraX. Looks to me like the problem is that 2-character chain IDs are incompatible with fixed-width fields for LINK records, so they fall back to variable-width space-delimited text. 

(on behalf of the co-authors, I have to say that the model is unpublished and confidential)

OpenGL version: 3.3.0 NVIDIA 455.32.00
OpenGL renderer: TITAN Xp/PCIe/SSE2
OpenGL vendor: NVIDIA Corporation
Manufacturer: Dell Inc.
Model: Precision T5600
OS: CentOS Linux 7 Core
Architecture: 64bit ELF
Virutal Machine: none
CPU: 32 Intel(R) Xeon(R) CPU E5-2687W 0 @ 3.10GHz
Cache Size: 20480 KB
Memory:
	              total        used        free      shared  buff/cache   available
	Mem:            62G        9.0G         36G        223M         16G         52G
	Swap:          4.9G          0B        4.9G

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	03:00.0 VGA compatible controller [0300]: NVIDIA Corporation GP102 [TITAN Xp] [10de:1b02] (rev a1)	
	Subsystem: NVIDIA Corporation Device [10de:11df]	
	Kernel driver in use: nvidia
Locale: ('en_GB', 'UTF-8')
PyQt5 5.15.2, Qt 5.15.2
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File attachment: model_2b_working_noh_real_space_refined.pdb

model_2b_working_noh_real_space_refined.pdb​

[Tristan Croll]

Added by email2trac

[pett]

So you're saying that ChimeraX wrote these LINK records, is that right?

[Tristan Croll]

No - these were written by Phenix. When loaded in ChimeraX, most of the bonds aren't formed.
________________________________
From: ChimeraX <ChimeraX-bugs-admin@cgl.ucsf.edu>
Sent: 29 March 2021 21:32
Cc: pett@cgl.ucsf.edu <pett@cgl.ucsf.edu>; Tristan Croll <tic20@cam.ac.uk>
Subject: Re: [ChimeraX] #4430: Hybrid-36 LINK records

#4430: Hybrid-36 LINK records
------------------------------------+----------------------------
          Reporter:  Tristan Croll  |      Owner:  Eric Pettersen
              Type:  defect         |     Status:  accepted
          Priority:  normal         |  Milestone:
         Component:  Input/Output   |    Version:
        Resolution:                 |   Keywords:
        Blocked By:                 |   Blocking:
Notify when closed:                 |   Platform:  all
           Project:  ChimeraX       |
------------------------------------+----------------------------

Comment (by Eric Pettersen):

 So you're saying that ChimeraX wrote these LINK records, is that right?

--
Ticket URL: <https://plato.cgl.ucsf.edu/trac/ChimeraX/ticket/4430#comment:2>
ChimeraX <http://www.rbvi.ucsf.edu/chimerax/>
ChimeraX Issue Tracker

[pett]

Well, those LINK records are illegal, even for Hybrid-36. Hybrid-36 works by conscripting the space character between the residue name and the chain ID for a second chain ID letter. These LINK records output by Phenix are pushing things into totally unrelated columns. The columns for a LINK record are defined here: ​http://www.wwpdb.org/documentation/file-format-content/format33/sect6.html#LINK

For example, in the first LINK record in the file, the first 'AF' chain ID is in columns 22 and 23 (instead of 21 and 22, where they should be), which puts the 'F' in the residue-sequence-number columns. Similarly, the '9' in '29' is pushed into the insertion-code column, and things just get worse from there.

You need to get Phenix to fix the LINK records they are writing out.

[Tristan Croll]

OK. Will bring it up with them.
________________________________
From: ChimeraX <ChimeraX-bugs-admin@cgl.ucsf.edu>
Sent: 29 March 2021 21:50
Cc: pett@cgl.ucsf.edu <pett@cgl.ucsf.edu>; Tristan Croll <tic20@cam.ac.uk>
Subject: Re: [ChimeraX] #4430: Hybrid-36 LINK records

#4430: Hybrid-36 LINK records
------------------------------------+----------------------------
          Reporter:  Tristan Croll  |      Owner:  Eric Pettersen
              Type:  defect         |     Status:  accepted
          Priority:  normal         |  Milestone:
         Component:  Input/Output   |    Version:
        Resolution:                 |   Keywords:
        Blocked By:                 |   Blocking:
Notify when closed:                 |   Platform:  all
           Project:  ChimeraX       |
------------------------------------+----------------------------

Comment (by Eric Pettersen):

 Well, those LINK records are illegal, even for Hybrid-36.  Hybrid-36 works
 by conscripting the space character between the residue name and the chain
 ID for a second chain ID letter.  These LINK records output by Phenix are
 pushing things into totally unrelated columns.  The columns for a LINK
 record are defined here: http://www.wwpdb.org/documentation/file-format-
 content/format33/sect6.html#LINK

 For example, in the first LINK record in the file, the first 'AF' chain ID
 is in columns 22 and 23 (instead of 21 and 22, where they should be),
 which puts the 'F' in the residue-sequence-number columns.  Similarly, the
 '9' in '29' is pushed into the insertion-code column, and things just get
 worse from there.

 You need to get Phenix to fix the LINK records they are writing out.

--
Ticket URL: <https://plato.cgl.ucsf.edu/trac/ChimeraX/ticket/4430#comment:4>
ChimeraX <http://www.rbvi.ucsf.edu/chimerax/>
ChimeraX Issue Tracker

[pett]

I have also improved the PDB I/O code to handle 2-character chain ID LINK and SSBOND records, once Phenix outputs legal ones.