Dear Eleanor,
Many thanks for you comments.
I have run aimless/pointless with those data sets having unit cell (134/67,
134/67, 183, 90, 90 120) previously integrated with P31 2 1.
Previously, I forced aimless to not determine laue group, to keep the original
SG, and now I let aimless determine
Donghyuk - testing your "twinning" in a lower symmetry space group can be
misleading.
Many checks look to see if twin related reflections are similar.
But the twin laws are often the same as the symmetry operators, so if you
have ignored the true symmetry, you will wrongly assume you have twinning.
Dear Randy,
Thank you for the important information and the useful link. I have another
question to bother you.
How accurately can these twining assessment programs report the data? What
could prevent these programs from reporting twinning data? (Twinned data are
reported as untwinned data)
Dear Lan,
Yes, that’s a serious problem that has led some people astray, including a few
papers where people got apparently good R-factors by invoking non-existent
twinning.
You can find a brief discussion of this point on the CCP4 wiki
(https://strucbio.biologie.uni-konstanz.de/ccp4wiki/index
Hi Randy,
> As Jacob and others have mentioned, you will always get lower R-factors once
> you treat the data as being twinned, and the more twin operators the bigger
> the reduction in R-factors.
Do normal data with no twinning, but refined with twin operator(s), show
similar phenomenon?
Donghyuk:
How good were your original images? If the paeks are sharp and clean, your processing could be easier; or you need more efforts. The data processing statistics is more important for troubleshooting.
Your showed an apparent SG of p6322, but it does have to be exact, especially when wit
N)CS.
> >
> > Hope this makes my remark a little clearer.
> >
> > Best,
> > Herman
> >
> > PS: While other BB readers may have had the same question, I have posted
> > the reply to the BB. I hope you don't mind.
> >
> >
> > -
[mailto:p.du...@ibmc-cnrs.unistra.fr]
Gesendet: Freitag, 11. Januar 2019 11:52
An: Schreuder, Herman /DE
Cc: CCP4BB@JISCMAIL.AC.UK
Betreff: Re: [ccp4bb] AW: [ccp4bb] AW: [EXTERNAL] [ccp4bb] translational NCS &
twinning
Le Vendredi 11 Janvier 2019 09:07 CET, herman.schreu...@sanofi.com a écrit:
That P6322 Xtriage shows pretty clearly that you have good data, and that
it is not twinned..
So I think you stick with that spacegroup - introducing false twin laws to
explain true crystal symmetry reduces the R values at the expense of
getting clear electron density.
You could process the data
Hi,
I'm just catching up on the BB after the CCP4 Study Weekend!
Going back to the beginning of this thread, it's true that tNCS and twinning
have opposite effects on the intensity moments, which can mask each other.
However, for simple cases (as this one appears to be) with a single NCS
tran
; Herman
>
> PS: While other BB readers may have had the same question, I have posted the
> reply to the BB. I hope you don't mind.
>
>
> -Ursprüngliche Nachricht-
> Von: Guan, Lan [mailto:lan.g...@ttuhsc.edu]
> Gesendet: Donnerstag, 10. Januar 2019 20:53
> A
Januar 2019 20:53
An: Schreuder, Herman /DE
Betreff: Re: [ccp4bb] AW: [EXTERNAL] [ccp4bb] translational NCS & twinning
Dear Herman,
I have read your insightful comments on twining and tNCS for years now, which
is very useful and helpful! Thanks,
For Donghyuk’s case, do you think that he re
Dear all,
Thank you very much for all of your suggestions and sharing experiences.
As many of you commented, the current small unit cell C2 refinement seems to be
incorrect or correct, and I should put some efforts to crack this question.
- To Phill Jeffrey,
The idea, trying to find high symmet
For two projects in the distant past, we dealt with tNCS by initially telling
lies to the software (1szp and 3pkz). The tNCS was strong enough that there
was a clear weak/dark pattern in the diffraction pattern, so for the initial
molecular replacement we used a data set in the smaller unit cel
On Thursday, January 10, 2019 2:11:52 AM PST Donghyuk Shin wrote:
> Dear all,
>
> I am having tough time with my Xtal data sets those seem to be twinned or
> have translational NCS, and it will be greatly appreciated if you can give me
> some advices or comments!
>
> Data was initially processe
Donghyuk
The combination of two things gives me cause for concern:
1. You've reindexed something that apparently scaled OK in point group
622 into point group 2, with a smaller cell. Since it's hard to fake
that sort of data agreement in 622, I assume your data is at the very
least pseudo-62
lly.
Best,
Herman
-Ursprüngliche Nachricht-
Von: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] Im Auftrag von Donghyuk
Shin
Gesendet: Donnerstag, 10. Januar 2019 11:12
An: CCP4BB@JISCMAIL.AC.UK
Betreff: [EXTERNAL] [ccp4bb] translational NCS & twinning
Dear all,
I am having toug
Dear Jacob Keller and Vipul,
Thank you both very much for the reply.
Regarding the R-values, I am just wondering whether the huge gap between
refinements w/ w/o twin operator can be possible even the crystal is not
twinned?
Best wishes,
Donghyuk
>>I feel you went ahead with right strategy.
I agree with this part regarding lowering symmetry.
>>For 2.1 A datasrt, the appropriate drop in Rfree/ Rwork is a strong
>>indicator, i believe.
This is not true—even non-twinned data will improve in R values with twinning
operators added as parame
Hi Donghyuk,
I feel you went ahead with right strategy.
For 2.1 A datasrt, the appropriate drop in Rfree/ Rwork is a strong
indicator, i believe.
If you have already build all possible model, using tls can be of further
help.
Cheers,
Vipul
On Thu 10 Jan, 2019, 3:52 PM Donghyuk Shin Dear all,
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