Thanks for the reply,
Does this mean REFMAC/Coot does need the missing number flags (and
thus you will get improved maps ONLY if uniqueify is run) or does
REFMAC/Coot recognise when a reflection is missing and use DFc
regardless (in which case there is no point running uniqueify)?
Simon
On 12 Mar 2008, at 16:00, George M. Sheldrick wrote:
All these programs only refine against reflections that were actually
measured. REFMAC, but not SHELXL, provides the 'Sigma-A' weight
coefficients for Coot to use DFc instead of 2mFo-DFc for the
reflections
for which Fo is not known (or is reserved for the free R) to
calculate a
map. This will in general improve the appearence of the map at the
cost
of introducing a little model bias. As far as I know these
'unobserved'
reflections are not used in calculating the difference map. CNS is
probably like SHELXL, I'm not sure what phenix.refine does.
George
Prof. George M. Sheldrick FRS
Dept. Structural Chemistry,
University of Goettingen,
Tammannstr. 4,
D37077 Goettingen, Germany
Tel. +49-551-39-3021 or -3068
Fax. +49-551-39-2582
On Wed, 12 Mar 2008, Simon Kolstoe wrote:
Dear CCP4bb,
I was looking through the REFMAC manual today and found the
following advice:
"Completing the data to include all possible hkls. Should do this
after data
reduction, and certainly before using REFMAC. This is now done with
the
uniqueify script. It is best done using CCP4i."
http://www.ccp4.ac.uk/dist/html/refmac5/usage/examples.html#exam0
Is it a good idea to always run uniqueify on data before running
REFMAC - what
about other refinement programs such as SHELX, CNS or phenix.refine?
Simon
