Re: [phenixbb] twin/pseudo-symmetry question

Hi Todd, There are 3 possible C2's you can choose from. Try besides R32 R3 C2 (no 1) C2 (no 2) C2 (no 3) P1 If you use labelit / imosflm you have full control over which spacegroup you can choose. HKL2000 doesn't provide enough control over which indexing solution you want to use. Alternatively, you could have an 'obverse/reverse twin' in R32, a special kind of reticular twin. In this twinning form, the hexagonal sublattice causes the twinning. When you index your data, check if the integral absences are indeed absent (when you are in the hexagonal setting). If not, you could have an obverse reverse twin. I have no clue about CCP4, but in phenix selecting the free set is done properly using the full symmetry of the lattice. If this is done incorrectly, you will get in trouble later down the line, so better make sure that things are ok. P On 11 November 2011 10:03, Green, Todd wrote:

For the R32 set, I generate the r-free in phenix directly from the scalepack file for data processed in R32. For C2, it was generated from the C2 processed scalepack file but in ccp4 using the scalepack2mtz script then imported to phenix(because i used molrep for the molecular replacement). But, I kept this same data file with the same r-free for all of the refinement runs before and during twin refinement. Seem reasonable?

-Todd

-----Original Message----- From: [email protected] on behalf of Nathaniel Echols Sent: Fri 11/11/2011 11:53 AM To: PHENIX user mailing list Subject: Re: [phenixbb] twin/pseudo-symmetry question

On Fri, Nov 11, 2011 at 9:47 AM, Green, Todd wrote:

...

the true space group is C2. Are these r-values too low? does the difference in values according to each twin law mean something?

I don't know enough to answer the rest of the question, but one thing to look out for is how you generate the R-free flags - which program did you use, and when you reprocessed in C2, did you generate a new set of R-free flags?  If you're not careful with this, you can end up severely biasing R-free when performing twinned refinement.

-Nat _______________________________________________ phenixbb mailing list [email protected] http://phenix-online.org/mailman/listinfo/phenixbb

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