[ccp4bb] P21, twinned date & NCS refinement

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CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Substituting zero vs. Fc for unobserved reflections
From: Gregg Crichlow gregg {- dot -} crichlow {- at -} YALE {- dot -} EDU
Date: 2012-03-27

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Subject: Re: Substituting zero vs. Fc for unobserved reflections
From: Ethan Merritt merritt {- at -} U {- dot -} WASHINGTON {- dot -} EDU
Date: 2012-03-27

Subject: P21, twinned date & NCS refinement
From: "Bosch, Juergen" jubosch {- at -} JHSPH {- dot -} EDU
Date: 2012-03-27

Dear CCP4BBers and PhenixBBers (cross posting here, since we all read both anyhow)

to the experts out there here's my question:

We have a P21 dataset with 2 molecules in the asu and a refined twin fraction of 38% according to phenix.refine using a twin law operator.

My gut feeling tells me that I can't use NCS unless I detwin the data, is that a correct assumption ?

How does phenix.refine [PDB] [mtz] twin_law="h,-k,-l" main_ncs=true would deal with this problem ?

Same question goes to Garib, it's very convenient to just specify twin in your Refmac script without further values and magic happens but what if I add NCS restrains, will Refmac treat them correctly according to the twin operator ?

Twins are confusing in real life and even more in crystals I think.

And no the data can not be processed in a higher space group, P222 results in Rmerges of >40% in the lowest resolution shell, the beta angle is 92.4 degrees in P21. And if processed in P1 we get 4 molecules per asu and a refined twin fraction of 50%, which in my eyes clearly indicates it's not P1 but really P21.

Hope to get some interesting feedback on this issue.

Thanks,

Jürgen

......................
Jürgen Bosch
Johns Hopkins University
Bloomberg School of Public Health
Department of Biochemistry & Molecular Biology
Johns Hopkins Malaria Research Institute
615 North Wolfe Street, W8708
Baltimore, MD 21205
Office: +1-410-614-4742
Lab: +1-410-614-4894
Fax: +1-410-955-2926
http://web.mac.com/bosch_lab/

CCP4bb navigation

CCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999

Previous message:
Subject: Substituting zero vs. Fc for unobserved reflections
From: Gregg Crichlow gregg {- dot -} crichlow {- at -} YALE {- dot -} EDU
Date: 2012-03-27

Next message:
Subject: Re: Substituting zero vs. Fc for unobserved reflections
From: Ethan Merritt merritt {- at -} U {- dot -} WASHINGTON {- dot -} EDU
Date: 2012-03-27