Re: [ccp4bb] translational NCS & twinning

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?

Re: [ccp4bb] translational NCS & twinning

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

[ccp4bb] AW: [ccp4bb] AW: [ccp4bb] AW: [EXTERNAL] [ccp4bb] translational NCS & twinning

Le Vendredi 11 Janvier 2019 12:18 CET, a écrit: Thank you Herman you for this clear and informative comments !! Particularly your last point, which I found very instructive. Now I remember the title of the article by T.O. Yeates "Protein crystals and their evil twins" in 1999. And this correspo

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[ccp4bb] AW: [ccp4bb] AW: [ccp4bb] AW: [EXTERNAL] [ccp4bb] translational NCS & twinning

Dear Philippe, As Randy just pointed out, when twinning, pseudosymmetry and other pathologies come into play, things really get complicated. I agree with what you said but for the current problem, things may be more complicated. To summarize: - "bona fide" twinning: there are two different, i

Re: [ccp4bb] translational NCS & twinning

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

Re: [ccp4bb] translational NCS & twinning

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

Re: [ccp4bb] AW: [ccp4bb] AW: [EXTERNAL] [ccp4bb] translational NCS & twinning

Le Vendredi 11 Janvier 2019 09:07 CET, herman.schreu...@sanofi.com a écrit: Dear Herman, As far as I understood the twinning problem, what you say is only true in some occasions, and not in others. If the "macroscopic" domains are so small that they are smaller than the X-rays coherence length,

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[ccp4bb] AW: [ccp4bb] AW: [EXTERNAL] [ccp4bb] translational NCS & twinning

Dear Lan, Thank you for your compliment. I do not use Xtriage, so I did not bother looking at the log files. What I meant to say is that with twinning, the crystal has different macroscopic domains where the molecules have different orientations, say one domain with orientation A and one domai