Dear Kay.
If it is still relevant, the following article by Kleywegt and Jones also look
at the correlation between R and Rfree as a function of resolution and find it
to be: Rfree = 1.065*R + 0.036.
Kleywegt GJ, Jones TA.
"Homo crystallographicus--quo vadis?"
Structure. 2002 Apr;10(4):465-72.
http://www.ncbi.nlm.nih.gov/sites/entrez?TermToSearch=11937051
Best Regards
Bjørn
--
Bjørn Pañella Pedersen
Ph.D Student, MSc
Department of Molecular Biology Office: +45 89425021
University of Aarhus Lab: +45 89425010
Gustav Wieds Vej 10c Email: [EMAIL PROTECTED]
DK-8000 Aarhus C Lab WWW: http://www.bioxray.dk
Denmark
Miller, Mitchell D. wrote:
Have a look at
Rfree and the Rfree Ratio. I. Derivation of Expected Values of
Cross-Validation Residuals Used in Macromolecular Least-Squares
Refinement. Tickle IJ, Laskowski RA and Moss DS
Acta Cryst. (1998). D54, 547-557
http://dx.doi.org/10.1107/S0907444997013875
and
Rfree and the Rfree ratio. II. Calculation of the expected values and
variances of cross-validation statistics in macromolecular least-squares
refinement. Tickle IJ, Laskowski RA and Moss DS Acta Cryst. (2000). D56,
442-450 http://dx.doi.org/10.1107/S0907444999016868
Regards,
Mitch
-----Original Message-----
From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Kay Diederichs
Sent: Thursday, November 15, 2007 8:42 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: [ccp4bb] difference of R_work and R_free as a function of resolution
Dear crystallographers,
today I explained to a student that I believe that the difference of
R_work and R_free should decrease as a function of resolution, because
at high resolution there is less danger of overfitting, whereas at low
resolution one is always overfitting to some extent. I'd say this should
be true at least in absolute terms, but probably even in relative terms:
for example, for a 1.5A structure I'd expect R_work/R_free= 14%/16%,
whereas at 3A I'd expect 28%/35%.
I believe that I saw plots (maybe in a link given in a posting on
CCP4BB) obtained for structures from the PDB, which confirmed this
hypothesis. But I've been googling and searching through postings now
for quite some while, and cannot seem to find anything to that effect.
Does anybody have a pointer to an analysis of this effect?
thanks,
Kay
P.S. Would be good to put this into the CCP4 Wiki article on R-factors
