Quick navigation:        Home   |    Site Map   ||    References   |    Biography   ||    Copyright   |    Other copyright   |    Contact us   |   
Protein structure
 

Re: [ccp4bb] MAD and twinning
 

Basic tutorials: 		 
 

CCP4bb navigation

CCP4bb <-- 2007 <-- April 2007 <-- 24 April 2007
Previous message:
Subject: MAD and twinning
From: Jordi Benach jb1343 {- at -} COLUMBIA {- dot -} EDU
Date: 2007-04-24 		Next message:
Subject: Re: MAD and twinning
From: Philippe DUMAS p {- dot -} dumas {- at -} IBMC {- dot -} U-STRASBG {- dot -} FR
Date: 2007-04-24


Subject: Re: MAD and twinning
From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK
Date: 2007-04-24
Well - it is pretty tricky to get reliable anomalous signal after
detwinning, but I guess you can try!

There are 2 ways I would test - one is detwin assigning I+ and I- - it
is meant to handle the anom pairs correctly.. You can input the twin
operator and the twin factor.

Then SFCHECK will also detwin data - but you will need to read the
manual to see if it will handle anomaous data properly..

Eleanor

Jordi Benach wrote:
> 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
>
>
>

CCP4bb navigation

CCP4bb <-- 2007 <-- April 2007 <-- 24 April 2007
Previous message:
Subject: MAD and twinning
From: Jordi Benach jb1343 {- at -} COLUMBIA {- dot -} EDU
Date: 2007-04-24 		Next message:
Subject: Re: MAD and twinning
From: Philippe DUMAS p {- dot -} dumas {- at -} IBMC {- dot -} U-STRASBG {- dot -} FR
Date: 2007-04-24


ProteinCrystallography.org: Copyright 2006-2008 by Quid United Ltd