[phenixbb] Very low resolution data set

[Pavel Afonine]

>> 1 What is the expected Rfree and Rwork for such low resolution data? I looked up PDB bank, and there is a 11.5A crystal with Rfree=~0.4. But not sure whether there is a kind of value for Rfree to consider the refinement works or not.
> It's difficult to come up with any meaningful statistics, because
> these structures are usually barely refined, for obvious reasons.
> (R-free in the high 30s is not uncommon for published structures,
> however.)  I don't understand the math well enough to know what to
> expect, but I've seen R-factors in the mid-to-low 40s for structures
> refined against nonsense low-resolution data (again ~6Å).  An R-free
> of 0.49 is very suspicious.

It can be anything, and low too. Just take any known structure, cut data 
at 15A and compute R, you may get 10% for well placed molecules.

This and references therein may help to set expectations:
http://journals.iucr.org/d/issues/2012/06/00/wd5173/index.html

Pavel