Hi Evette,

(1) best practices in refining against  lower resolution data (~4 angstrom)
> to achieve the best model,
>


obtain a model that fits data best under requirement that it has zero
geometry violations (Ramachandran, Cbeta deviations, rotamers, CABLAM,
etc..).

Note, a geometry outlier (Ramachandran plot outlier, for instance) does not
necessarily mean wrong. Example of a valid outlier: page 21 here:
http://phenix-online.org/presentations/latest/pavel_validation.pdf

However, low-resolution data is unlikely to justify outliers, that's why
zero is the goal (unless there is no other strong reasons to support the
outlier).


> One might encounter a hypothetical situation where standard refinement
> approaches gave a model with poor Ramachandran statistics.  Imposing
> Ramachandran restraints gave a model with improved Ramachandran statistics
> but at the expense of higher Rfree.
>

This is likely a software issue or incorrect use by the user. Contact
refinement software developers to resolve the issue.

Pavel

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