standard deviations for cell constants

Rob Hooft Rob.Hooft at
Mon Jun 10 07:25:35 EST 1996

Zbyszek Otwinowski <zbyszek at> writes:

> Conclusion:
> There is no sensible procedure for reporting
> error of the unit cell. Fortunatelly it does not matter, as the error
> is very small.

However, after the refinement of a structure with inaccurate cell
parameters, a systematic deviation of the bond lengths in the
structure can be detected. The effect may be "marginal" in many cases,
but in over 50% of all protein structures in the PDB it is detectable
at the >99.99% confidence level! In some cases, the error is >2% in one
of the axis lengths.

In one particular case known to us, the crystallographer --worried by
the warning message from our software-- found a problem in the dataset.
Solving the problem resulted in a 1% drop in R.

For software and results see:


Rob Hooft.

=== Rob.Hooft at EMBL-Heidelberg.DE   http://www.Sander.EMBL-Heidelberg.DE/rob/ ==
==== In need of protein modeling?  http://www.Sander.EMBL-Heidelberg.DE/whatif/
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