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: [log in to unmask]
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:[log in to unmask]] On Behalf Of Kay Diederichs
>> Sent: Thursday, November 15, 2007 8:42 AM
>> To: [log in to unmask]
>> 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
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