On 29.08.2008, at 03:16, Ian Tickle wrote:
> You don't really need a program: e.g. if there are N non-H atoms
> refined, then there are 4N params (isotropic B) or 9N (aniso). TLS
> adds
> 19 params per group to the isotropic count. You count unique
> reflections.
That simple count doesn't take into account restraints, however.
A while ago I looked at data/parameter ratios in PDB structures and
was surprised at how small they can get. There are some histograms
with a bit of analysis at
http://dirac.cnrs-orleans.fr/plone/Members/hinsen/data-parameter-
ratio-in-x-ray-structure-determination
for those who are interested.
Konrad.
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Konrad Hinsen
Centre de Biophysique Moléculaire, CNRS Orléans
Synchrotron Soleil - Division Expériences
Saint Aubin - BP 48
91192 Gif sur Yvette Cedex, France
Tel. +33-1 69 35 97 15
E-Mail: [log in to unmask]
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