Hi Nat, Kelly, Kay and Jürgen,
I also prefer the I422 with 1 mol/ASU since all the analysis pointed to higher symmetry. I will refine with I422 and report back.
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The xtriage log for I422 data says high combined Z-score:
The quarter of Intensities *least* affected by the anisotropy correction show
<I/sigI> : 3.45e+00
Fraction of I/sigI > 3 : 4.09e-01 ( Z = 4.02 )
The quarter of Intensities *most* affected by the anisotropy correction show
<I/sigI> : 1.54e+00
Fraction of I/sigI > 3 : 7.20e-02 ( Z = 12.06 )
The combined Z-score of 12.71 indicates that there probably is significant
systematic noise amplification that could possibly lead to artefacts in the
maps or difficulties in refinement
______________________
Thanks,
Tongqing
Tongqing Zhou, Ph.D.
Staff Scientist
Structural Biology Section
Vaccine Research Center, NIAID/NIH
Building 40, Room 4609B
40 Convent Drive, MSC3027
Bethesda, MD 20892
(301) 594-8710 (Tel)
(301) 793-0794 (Cell)
(301) 480-2658 (Fax)
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-----Original Message-----
From: Nathaniel Echols [mailto:[email protected]]
Sent: Tuesday, May 08, 2012 1:25 PM
To: PHENIX user mailing list
Subject: Re: [phenixbb] UPDATE-- Difficult dataset and refinement--P422? I422?Twinning?
On Tue, May 8, 2012 at 10:08 AM, Kelly Daughtry <[email protected]> wrote:
>> 1. Is it really twinned since including twin-law in refinment gave
>> much better numbers?
> I would say, it likely is twinned
Actually, Xtriage says not:
The results of the L-test indicate that the intensity statistics behave as expected. No twinning is suspected.
The symmetry of the lattice and intensity however suggests that the input space group is too low. See the relevant sections of the log file for more details on your choice of space groups.
Twinned refinement can be deceptive because it often lowers the R-factors even if twinning isn't present - Garib Murshudov warns about this in his talks on the subject.
-Nat
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