Hi Mark,
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
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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: [EMAIL PROTECTED]
http://sb.web.psi.ch
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