Dear Prem,
you also need to count the number of restraints as observations and
constraints, which reduce the number of parameters. The number of restraints
at this resolution might exceed the number of observations. If I remember
correctly, the numbers are listed in the refmac5 log file and pro
Dear all,
How observation is to parameter ratio is determined for a crystal
structure. Suppose If we have only one observation for each parameter at a
resolution of say 2.9 Angstrom, how terribly it is easy to overfitt for the
data to get a misleading agreement between model and experiment ? Is the
On Wed, 2009-09-23 at 16:05 +0200, Dirk Kostrewa wrote:
>
> yes, but this is only in case of torsion angle refinement. For x,y,z
> the determinancy point is ~3 A.
>
True, but to count all the x,y,z,b as parameters is only sensible with
unrestrained refinement. If restraints are properly impose
I've seen this estimate of the determinancy point for torsion angle
refinement presented by Axel Brunger at ACA meeting this summer. I
don't remember all the details, but no, it did not refer to the approach
described in the paper where higher resolution model is used as a
restraint. It was simpl
Brunger, A., DeLaBarre, B., Davies, J. & Weis, W. X-ray structure
determination at low resolution. ACTA CRYSTALLOGRAPHICA SECTION
D-BIOLOGICAL CRYSTALLOGRAPHY 65, 128-133 (2009).
The paper quotes Wayne Hendrickson (says "submitted") regarding
"determinancy" point (i.e. where the number of obse
Dear Ed Pozharski,
Am 23.09.2009 um 15:48 schrieb Ed Pozharski:
Take a look at this:
Brunger, A., DeLaBarre, B., Davies, J. & Weis, W. X-ray structure
determination at low resolution. ACTA CRYSTALLOGRAPHICA SECTION
D-BIOLOGICAL CRYSTALLOGRAPHY 65, 128-133 (2009).
The paper quotes Wayne Hendri
Take a look at this:
Brunger, A., DeLaBarre, B., Davies, J. & Weis, W. X-ray structure
determination at low resolution. ACTA CRYSTALLOGRAPHICA SECTION
D-BIOLOGICAL CRYSTALLOGRAPHY 65, 128-133 (2009).
The paper quotes Wayne Hendrickson (says "submitted") regarding
"determinancy" point (i.e. wher
Hi Hugh
A data/parameter ratio of 0.5 does seem low even at 3.4 Ang, I would
expect it closer to 1 (say 0.8 to 0.9) depending on the solvent content.
Why is it low - is your completeness low? What matters from the point
of view of what Rfree you should expect, all being well, is the
observation/p
Dear Hugh Morgan,
this ratio is only true if you refine your atomic model without any
geometrical restraints against the observed X-ray data. If you include
parameters for ideal geometry, you add ideal bond lengths, angles,
chiral volumes, planar groups and dihedral angles as additional
"
Hi,
We are attempting to address a referees comment concerning our
data/parameter ratio for a 3.4 A structure. Although the ratio is only 0.5, the
R/Rfree is 25/29, which seems acceptable. Ideally I would like to include a
reference showing a graph or table of data:parameter vs resolution b
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