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RE: [ccp4bb]: Twinning/Merging



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Daniel,

Why do you think the data set (s) are twinned?

It would be useful to run truncate and look at the cumulative intensity
distributions for each of your data sets. The observed curves should be very
close to the theoretical curves.  If not then there is something wrong with
the data set, one possibility maybe twinning.

Regards
**********************************************
Chris F. Snook, Ph.D.                     email : snookc@missouri.edu      
Dept Biochemistry                        phone : (573)-884-2302         
Univ. of Missouri                           FAX   : (573)-884-4812         
117 Schweitzer Hall

Columbia

MO 65211

______________________________________________

> ----------
> From: 	Daniel Schlieper
> Sent: 	Friday, December 15, 2000 8:22 AM
> To: 	ccp4bb@dl.ac.uk
> Subject: 	[ccp4bb]: Twinning/Merging
> 
> ***  For details on how to be removed from this list visit the  ***
> ***    CCP4 home page http://www.dl.ac.uk/CCP/CCP4/main.html    ***
> 
> Dear all,
> 
> Of one protein, I used 3 crystals to collect a data set at room
> temperature. The data set is to 96 % complete, diffracts to 2.35 A,
> and has a very high Rmerge value after scalepack: 16 % (77 % in the
> 2.38-2.35 A shell). 
> 
> The twinning test (from Yeates, www.doe-mbi.ucla.edu/Services/Twinning/) 
> gave no twinning at all.
> 
> I used the very same protein to grow crystals of the very same crystal
> form. (The crystals differ in the substrate co-crystallized). These
> crystals were measured at 100 K, and I collected full data sets of
> every crystal. Tested for twinning, it came true, that all of them
> were twins of 5-15% (P3221, (-h,-k,l)).
> 
> Now I wonder if the 3 crystals measured at room temperature have been
> twins as well, and if I may explain the high R-value with that. Is
> this true?
> 
> See you in York!
> 
> Best regards, Daniel
> 
> -- 
> Daniel Schlieper                      Institut fuer Biochemie
>                                       Zuelpicher Strasse 47
> Daniel.Schlieper@Uni-Koeln.De         Universitaet zu Koeln 
> Tel.: +49 221 470-6443, Fax: -5092    50674 Koeln, Germany
> 
> 
> -- 
> Daniel Schlieper                      Institut fuer Biochemie
>                                       Zuelpicher Strasse 47
> Daniel.Schlieper@Uni-Koeln.De         Universitaet zu Koeln 
> Tel.: +49 221 470-6443, Fax: -5092    50674 Koeln, Germany
>