[phenixbb] R/R free reported values

Nathaniel Echols nechols at lbl.gov
Mon Oct 27 16:43:26 PDT 2014

On Mon, Oct 27, 2014 at 1:19 PM, George Devaniranjan <devaniranjan at gmail.com
> wrote:

> Would you define "significant" for me (as you see it of course)?

Pavel's definition:


"...the difference between R factors computed using the different methods
is typically less than 0.01%."

I think this is probably a typo and it is supposed to mean "1%" or "0.01",
which would have been my estimate.  Certainly differences below 0.005 are
hardly worth noticing, and below 0.001 is statistical noise.  Differences
above 0.01 are more worrisome (although not entirely unheard of).

I am NOT a X-ray crystallographer but I was intrigued by this post. I have
> RE-refined structures and have seen R/R (Free) go up say by 0.4
> Say from 0.110 to 0.150
> Would you say that is significant for high resolution structures ?

Yes.  It may reflect a sub-optimal refinement strategy, although I have
seen this happen occasionally when re-refining (in Phenix) an
ultra-high-resolution structure previously refined with SHELX.

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