Dear Sergei,
since your Rmerge is high at low resolution even in P1, my guess is,
that there was a problem either with the crystal or with the data
collection. Fine slicing should improve the data quality, because your
get a better description of the reference profiles and reduce the
background. Different merging of fine-sliced images into
"coarser-sliced" images was already systematically done by Wolfgang
Kabsch, with the result, that finer slices gave better results, although
slices much finer than half the full mosaicity angle of a reflection
didn't improve the results much further (I've heard a talk given by
Wolfgang, but never found a publication about these results). There is a
publication in 1999 about fine-slicing by Jim Pflugrath, that you might
want to read about this (Acta Cryst D55, 1718-1725). So, merging
fine-sliced images into coarse-sliced probably won't help.
Anyway, good luck!
Dirk.
Am 05.11.10 09:40, schrieb Sergei Strelkov:
Dear All,
I am processing a dataset collected (not by me) with 0.1 degree
oscillations.
The diffraction is quite weak even though there is a clean diffraction
pattern to about 3A.
Either Mosflm or XDS processes the data readily with +/- default settings
but both yield a high overall Rmerge of about 0.23 in the expected
symmetry.
Processing in P1 yields an overall Rmerge of ~0.18, but what is
especially disappointing
is that Rmerge is as high as 0.15 at ~5A resolution already.
The question is, how can we process the data so that the merging
statistics
becomes more reasonable?
Apparent mosaicity turns out to be ~0.5A. My naive way of thinking is
to try treating each five consecutive frames as a single 0.5 degree
frame.
Does anyone have experience with this?
Many thanks in advance,
Sergei
--
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Dirk Kostrewa
Gene Center Munich, A5.07
Department of Biochemistry
Ludwig-Maximilians-Universität München
Feodor-Lynen-Str. 25
D-81377 Munich
Germany
Phone: +49-89-2180-76845
Fax: +49-89-2180-76999
E-mail: kostr...@genzentrum.lmu.de
WWW: www.genzentrum.lmu.de
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