Without seeing the raw data and watching the integration of frames, I
would be suspicious of an incorrect space group assignment with an
Rmerge 0.10. Are image spots well-predicted by the integration program
(all spots have predictions, all predictions have spots)? Are the spots
well-resolved
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Dear Hamid,
the statistics for I/sigI and the R-value per resolution shell would
shed more light than the overall values.
Judging from the Rmerge in the high resolution shell the data may have
been processed by somebody who still thinks Rmerge = 30%
[CCP4BB@JISCMAIL.AC.UK] on behalf of hamid khan
[hamid...@yahoo.com]
Sent: Friday, March 29, 2013 8:19 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: [ccp4bb] High Rmerge and I/sigma values?
Dear CCP4BB Members,
I am interested in your expert comments/opinions about two values of a protein
crystal
I must disagree with Tim on the statement Rmerge should not be
published anymore. That would be a shame. Perhaps even a crime.
When Uli Arndt introduced Rmerge he was in no way, shape or form
proposing that it be used for resolution cutoffs, or anything else
about the quality of the structure.
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Hi James,
you misquote me: I was saying that Rmeas should be replacing Rmerge,
and I guess everything you say holds for Rmeas, too, but still it is a
better statistical quantity than Rmerge. So please replace Rmerge with
Rmeas.
Best,
Tim
On
Ahh. But what I'm saying is that Rmeas is not a replacement for
Rmerge because Rmeas is _always_ lower than Rmerge. It is even less
useful that a low-multiplicity Rmerge for evaluating the
diffractometer.
I fully realize that Rmeas does have the desirable property of being
flatter with respect
To support James Holton, MAD Scientist
From the very far past:
In 60's we have estimated X-ray diffraction data by eyes, using strips of
intensities made with propagating exposure factor increase of 2 (I guess in F
it corresponds to sqrt(2)~=1.4).
We have used to estimate our Weissenberg
Woops! Sorry. I was thinking Rpim, which is always lower than Rmerge.
Rmeas is always higher, and more correctly estimates the
infinite-multiplicity Rmerge.
Sorry for the confusion, and thanks for the many reminders I just got
about the definition!
-James Holton
MAD Scientist
On
