[phenixbb] Incorrect secondary structure assignment in a .pdb
Pavel Afonine
pafonine at lbl.gov
Thu Jun 28 09:38:11 PDT 2018
Hi Maciej,
please have a look at item #10 and Notes section here:
http://www.phenix-online.org/documentation/reference/real_space_refine.html
One sentence summary is: Make sure you use secondary structure (SS)
restraints in refinement, also making sure you provide SS annotations as
HELIX/SHEET records in input PDB that are as accurate as possible; this
is critical for successful refinement.
If you have more questions please get back to us!
Good luck!
Pavel
On 6/28/18 09:23, Maciej Jagielnicki wrote:
> Hi All,
>
> I used a combination of phenix real space refine and Coot to build a
> model into a cryoEM density map. I used an existing .pdb file as a
> starting point for my building. During the build, some helical
> elements became strands and vice versa (it was very clear to my eyes).
> Unfortunately, neither Phenix nor Coot would automatically update the
> header information for secondary structure elements, and I had to
> manually edit the header so that helices would show up in correct
> places when the .pdb file was viewed in Chimera or similar software.
> Not an ideal way of doing this which is likely related to what
> happened next.
>
> When the header information is removed, however, as it happens when
> the pdb.extract tool prepares a .pdb file for submission by turning it
> into a .cif file, the secondary structure elements are still displayed
> when a .cif file is visualized (bizzare in itself) but also the
> secondary structure is taken straight from the starting .pdb file (the
> one I used as a base for my model to which there is no connection
> whatsoever). The question is this - where does the incorrect secondary
> information come from in the absence of the header? How to fix this? I
> cannot deposit a file that shows helices/sheets wherever it wants...
>
> Regards,
> Maciej J.
>
> --
> Maciej Jagielnicki, MS.
> Graduate Student
> University of Virginia
> Molecular Physiology and Biological Physics
> 480 Ray C Hunt Drive Rm 320
> Charlottesville, VA
> Lab Phone: 434-243-2520
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