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Re: [ccp4bb] twin fraction varies between crystals? |
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CCP4bb navigationCCP4bb <-- 2007 <-- April 2007 <-- 18 April 2007Subject: Re: twin fraction varies between crystals? From: Dirk Kostrewa dirk {- dot -} kostrewa {- at -} PSI {- dot -} CH Date: 2007-04-18 thus far, in the many cases where we had merohedral twinning, the twin fraction varied usually a lot, ranging from ~0.1-0.5 for the same crystallization conditions. So, it's a good idea to screen a couple of crystals and check their twin fractions (estimating the true twin fraction is a completely different story ...). Good luck, Dirk. Mark Mayer wrote: > 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 -- **************************************** Dirk Kostrewa Paul Scherrer Institut Biomolecular Research, OFLC/110 CH-5232 Villigen PSI, Switzerland Phone: +41-56-310-4722 Fax: +41-56-310-5288 E-mail: dirk.kostrewa@psi.ch http://sb.web.psi.ch **************************************** CCP4bb navigationCCP4bb <-- 2007 <-- April 2007 <-- 18 April 2007 |
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