[ccp4bb] MAD and twinning

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CCP4bb <-- 2007 <-- April 2007 <-- 24 April 2007

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Subject: looking for 2-oxo-histidine library
From: adeline {- dot -} robin {- at -} IBS {- dot -} FR adeline {- dot -} robin {- at -} IBS {- dot -} FR
Date: 2007-04-24

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Subject: Re: MAD and twinning
From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK
Date: 2007-04-24

Subject: MAD and twinning
From: Jordi Benach jb1343 {- at -} COLUMBIA {- dot -} EDU
Date: 2007-04-24

Hi,

I just got a MAD dataset (~2.5A) of a crystal that so far seems to
belong to P31 or P32 space group and that also scales pretty well
in P3121 or P3221. According to the UCLA twinning server, the
P31/P32 crystal is merohedrally twinned with a twinning fraction of
0.33 and following a twinning operation h,-h-k,-l. CNS gives a
twinning fraction of 0.42.

Although we have solved twinned crystals in the lab with similar
twinning fractions/resolution in the past using SOLVE or BnP/SHELX,
only realizing that the crystal was twinned during refinement when
the R values wouldn't go down.

In this P31/P32 case, however, I can't solve the twinned data with
any program, or at least I can't get interpretable electron density
maps. Any ideas, clues? Is there a way to get a program that will
detwin raw intensity data (like *.sca files directly from
scalepack)?

Thanks,

Jordi

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CCP4bb <-- 2007 <-- April 2007 <-- 24 April 2007

Previous message:
Subject: looking for 2-oxo-histidine library
From: adeline {- dot -} robin {- at -} IBS {- dot -} FR adeline {- dot -} robin {- at -} IBS {- dot -} FR
Date: 2007-04-24

Next message:
Subject: Re: MAD and twinning
From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK
Date: 2007-04-24