Dear Andrea,
I agree with Tim and still cut the resolution at <I/sigma>=2. In my
experience, including higher resolution shells with poorer
signal-to-noise never changed the apparent resolution of the electron
density maps.
In addition, the high resolution limit at <I/sigma>=2 coincides very
well with the point where the Fo vs. Fo +Gauss(0,1)*sigma(Fo)
correlation coefficient curve, reported by BUSTER, crosses the
recommended lower limit of 0.9.
And please note, CC*=0.5 corresponds to CC(1/2)=0.143. In my very
limited experience, <I/sigma>=2 corresponds to roughly CC(1/2)~0.7.
Although I'm very excited about the CC(1/2) or CC* paper by Karplus &
Diederichs, I still prefer to be on the save side, until it has been
verified in numerous cases, that choosing high resolution cutoffs based
on CC(1/2) really leads to higher resolution structures. The recommended
procedure to include small resolution increments in refinement to decide
the high resolution cutoff is very time-consuming.
Best regards,
Dirk.
Am 13.06.13 17:15, schrieb Andrea Edwards:
Hello group,
I have some rather (embarrassingly) basic questions to ask. Mainly.. when
deciding the resolution limit, which statistics are the most important? I have
always been taught that the highest resolution bin should be chosen with I/sig
no less than 2.0, Rmerg no less than 40%, and %Completeness should be as high
as possible. However, I am currently encountered with a set of statistics that
are clearly outside this criteria. Is it acceptable cut off resolution using
I/sig as low as 1.5 as long as the completeness is greater than 75%? Another
way to put this.. if % completeness is the new criteria for choosing your
resolution limit (instead of Rmerg or I/sig), then what %completeness is too
low to be considered? Also, I am aware that Rmerg increases with redundancy, is
it acceptable to report Rmerg (or Rsym) at 66% and 98% with redundancy at 3.8
and 2.4 for the highest resolution bin of these crystals? I appreciate any
comments.
-A
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Dirk Kostrewa
Gene Center Munich
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
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