Re: [ccp4bb] twwining operator

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

Previous message:
Subject: twwining operator
From: siva charan siva {- dot -} charan {- at -} UNI-GRAZ {- dot -} AT
Date: 2007-05-21

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Subject: Molecular Replacement of a Known Anomalous Substructure
From: Jacob_Keller j-keller2 {- at -} NORTHWESTERN {- dot -} EDU
Date: 2007-05-21

Subject: Re: twwining operator
From: Phil Jeffrey pjeffrey {- at -} PRINCETON {- dot -} EDU
Date: 2007-05-21

Well there are no general twinning operators for a monoclinic space
group (e.g. like P3, P4) but there are two special cases which come to mind:

* beta=90 in which case the twinning operator is something like
(h,-k,-l) - pseudo primitive orthorhombic.
* where the monoclinic lattice lengths conspire to make your lattice
pseudo C-centered orthorhombic, in which case the twinning operator is
usually something like (h,k,-h-l) but not necessarily identical to that
depending on your cell.

I've had both of these happen to me.

Best way is to run CNS or mmtbx.xtriage (the latter useful for tests
other than twinning), both of which list the twin operators that they try.

Phil Jeffrey
Princeton, NJ

siva charan wrote:
> hello
>
> I have a data set to 2.4 A, which has space group of *P21 *. From the
> cumulative intensity distribution graph, indicates that data is
> twinned . To run the detwin program in ccp4, one has to know the
> twinning operator. Can anybody help me, how can I get the twinning
> operator for monoclinic space group. I have checked for twin operators
> at http://www.ccp4.ac.uk/dist/html/twinning.html, but there are no
> twining operators for monoclinic space group.
> regards
> siva

CCP4bb navigation

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

Previous message:
Subject: twwining operator
From: siva charan siva {- dot -} charan {- at -} UNI-GRAZ {- dot -} AT
Date: 2007-05-21

Next message:
Subject: Molecular Replacement of a Known Anomalous Substructure
From: Jacob_Keller j-keller2 {- at -} NORTHWESTERN {- dot -} EDU
Date: 2007-05-21