[ccp4bb] twin fraction varies between crystals?

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CCP4bb <-- 2007 <-- April 2007 <-- 17 April 2007

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Subject: Research/Senior Associate - Structural Biology
From: Sridhar Prasad SridharP {- at -} MBASIS {- dot -} COM
Date: 2007-04-17

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Subject: Re: twin fraction varies between crystals?
From: Peter Zwart PHZwart {- at -} LBL {- dot -} GOV
Date: 2007-04-17

Subject: twin fraction varies between crystals?
From: Mark Mayer mayerm {- at -} MAIL {- dot -} NIH {- dot -} GOV
Date: 2007-04-17

For cases where people have had merohedral twinning, did the twin fraction vary substantially
between individual crystals grown under indentical conditions? I have no prior experience with
merohedral twinning, and was surprised to see that the twin fraction varied substantially as detailed
below, and that by screening we were able to get untwinned xtals.

The project started with a weak home data set for which the twin fraction was 0.478, and which
scaled in both H3 and H32. We just came back from APS with data sets from another three crystals,
for which the ML twin fraction, estimated using phenix.xtriage with scalepack merged intensities as
input, varied from 0.335, 0.219 and 0.02. The latter is refining very nicely, in H3 and will not scale in
H32.

Thanks - Mark

CCP4bb navigation

CCP4bb <-- 2007 <-- April 2007 <-- 17 April 2007

Previous message:
Subject: Research/Senior Associate - Structural Biology
From: Sridhar Prasad SridharP {- at -} MBASIS {- dot -} COM
Date: 2007-04-17

Next message:
Subject: Re: twin fraction varies between crystals?
From: Peter Zwart PHZwart {- at -} LBL {- dot -} GOV
Date: 2007-04-17