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. where the number of observations becomes
equal to the number of flexible torsions (of course, in this extreme
case gemoetric restraints essentially become constraints and you don't
refine B-factrors at all.  With 50% solvent this is ~5.4A, and you are
far from that limit.

It is rather surprising that any reviewer anywhere would have doubts
about possibility to refine structural model at 3.4A.  While I don't
know what the referee said *exactly*, but he/she may be unaware of this

http://www.rcsb.org/pdb/statistics/histogram.do?mdcat=refine&mditem=ls_d_res_high&minLabel=0&maxLabel=5&numOfbars=10&name=Resolution



On Wed, 2009-09-23 at 12:48 +0000, hugh morgan wrote:

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 but I have been unable to find such a paper. Please

could someone point me in the right direction.

Thanks in advance

Hugh

P.S. It would be nice to know if this table has been published

http://www-structmed.cimr.cam.ac.uk/Course/Basic_refinement/Refinement.html

or something similar to this, which includes higher resolution

structures

http://dirac.cnrs-orleans.fr/plone/Members/hinsen/data-parameter-ratio-in-x-ray-structure-determination

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