Hi Jarros
On 03/14/2016 05:56 AM, Jarrod Mousa wrote:
> Hi all,
>
> I have two data sets for a protein that both index and scale into
> P212121 and process easily in imosflm, yet AIMLESS and Xtriage suggest
> twinning, although no laws fit P212121.
May I suggest you read the following references. It is not always very
easy detect a REAL twin in protein crystals ...
- Yeates & Fam (1995). Protein crystals and their evil twins. Structure.
7(2). R25-R29.
- Yeates (1997). Detecting and overcoming crystals twins. Methods in
Enzymology. 276. 344-358.
- Padilla & Yeates (2003). A statistical for local intensity differences
... Acta Cryst. D59, 1124-30, 2003
Usually you need more than just one indicator, and the REAL ones are not
detectable by images inspection.
Nevertheless, it is always very useful a visual inspection of your images.
Could you perhaps, try XDS and tell us about the <I**2>/2<I>**2 HIGHER
ORDER MOMENTS OF WILSON DISTRIBUTION OF ACENTRIC DATA
In my experience it is a good first indicator
You could also try http://services.mbi.ucla.edu/Twinning/
> I tried indexing into P1 and Xtriage finds three possible
> pseudo-merohedral twin laws h-k-l, -h,k-l, and -h,-k,l. I can find
> solutions easily in Phaser, but these will not refine Rfree. I am
> wondering what the best approaches are to find the correct spacegroup
> and try to solve the structure correctly?
If I understood correctly, you obtain "easily" MR solutions in P1 with
Phaser, could you tell us about the Z-scores and LLG ?
So then you tried refmac and the Rfree didn't goes down? or what?
What about your Rsym, Completeness, resolution and B-factors (wilson and
refinement ones)?
All the best
Carlos
>
> thanks,
>
> Jarrod Mousa
--
Carlos CONTRERAS MARTEL, Ph.D.
(CR1 CNRS)
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"Bacterial Pathogenesis Group"
Institut de Biologie Structurale
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