[phenixbb] Support for residues on symmetry elements - first reaction
Felix Frolow
mbfrolow at post.tau.ac.il
Sun Dec 27 11:58:37 PST 2009
Ralf ----- GREAT
However I do not get what it is ==1 and !=1
Are they have meaning or it is encoding striking back?
And to the last question: yes, it is good to keep
coordinates constrained to stay on the symmetry element. It should be
a default.
FF
Dr Felix Frolow
Professor of Structural Biology and Biotechnology
Department of Molecular Microbiology
and Biotechnology
Tel Aviv University 69978, Israel
Acta Crystallographica D, co-editor
e-mail: mbfrolow at post.tau.ac.il
Tel: ++972 3640 8723
Fax: ++972 3640 9407
Cellular: ++972 547 459 608
On Dec 27, 2009, at 20:24 , Ralf W. Grosse-Kunstleve wrote:
> The current development version of phenix.refine (dev-268 or later)
> supports residues located on symmetry elements, e.g. SO4 on a three-fold
> axis. phenix.refine now computes structure factors slightly differently
> compared to older versions.
> The new rules are:
>
> - Atoms with occupancy == 1 are subject to automatic handling of the
> symmetry.
> Example:
> An atom near a three-fold axis (distance to symmetry copy <= 0.5 A)
> is moved onto the axis and constrained in refinement to stay on
> the axis. The "special position factor" (1/3 is this case) is taken
> into account internally. The factor does not appear in the occupancy.
>
> - Atoms with occupancy != 1 are assumed to take the special position
> factor into account in the occupancy. Automatic handling of the
> symmetry is turned off.
> Example:
> A disordered SO4 molecule near a three-fold axis should have
> occupancies of 0.33 for all atoms.
>
> - If all atoms in a residue have occupancies != 1, all
> nonbonded symmetry interactions between the atoms in the
> residue are disabled.
>
> These three rules are meant
> - to bring phenix.refine in line with other programs and the PDB.
> - "to do the right thing" in most cases without manual intervention.
>
> Please let me know if you see problems with the new way phenix.refine
> uses occupancies to determine special position constraints and
> exclusions for nonbonded symmetry interactions.
>
> Does anyone need atoms with partial occupancies but constrained to
> stay on a symmetry axis during refinement?
>
> Ralf
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