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Re: [ccp4bb]: detwinning anomalous data
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Hi Ambrose,
I don't know if you have double checked this, but be sure that the twin
operation doesn't relate I+ to I-. In my case R3 with 20% twinning I+ was
related to I+ and I- was related to I- so I could do what you are
suggesting. However, I believe that not all twinning cases are like this.
Depending on your space group, I+ could be related to I- by the twin
fraction. Therefore, what you are proposing would not work.
This is just a caution. Maybe another CCP4 poster/reader has checked all
twinning possibilities to support or refute my caution. At least one
space group to be careful of is P6 with 2-fold twinning about a,b. This
combination relates I+ to I- by the twin operator making what you suggest
impractical.
Best of Luck,
Chris
PS. "Non-helpful Advice" - Find un-twinned crystals! If you found one
that was less twinned, keep searching. Worked for me - in the end.
On Thu, 13 Sep 2001, Ambrose R Cole wrote:
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> *** CCP4 home page http://www.ccp4.ac.uk ***
>
> I have been having lots of trouble with 50% twinning for a Se-met
> derivative that I am working on. Recently I have collected a data set
> which appears to be less twinned (33%). I would like to attempt to detwin
> this data set but keep the anomalous signal. Is it a good idea to
> seperate the F+ and F-, detwin and then join them back together if so how
> do I join them back together to create a normal mtz file with FP, DANO
> etc.
>
> any help would be greatly appreciated
> thanks
> Ambrose
>
>
Christopher L. Colbert, Ph.D.
Research Associate
Howard Hughes Medical Institute Phone: (214) 648 5002
University of Texas Southwestern Medical Center FAX: (214) 648 5095
5323 Harry Hines Boulevard
Dallas, TX 75390