Hi U
Well if you can tell me the total number of atoms in your PDB file (NOT
counting any H atoms), I can estimate a range for the expected optimal
Rfree assuming your value of Rwork and the no of reflns in your working
set (~= 19x1715 = 32585 right?). If you have any NCS I can't promise my
estimate will be very accurate, because it will also depend a lot on the
nature of the NCS, how you selected your test set, how you restrained
the NCS etc. I can already tell you that the range of optimal Rfree
(+/- 3 sd's) will be ~ +/- 0.014 (i.e. +/- 3x0.267/sqrt(2x1715)) from
whatever is the expected value.
Cheers
-- Ian
> -----Original Message-----
> From: [log in to unmask]
> [mailto:[log in to unmask]] On Behalf Of U Sam
> Sent: 20 June 2008 21:23
> To: Mark J. van Raaij; [log in to unmask]
> Subject: RE: [ccp4bb] How many reflections for Rfree?
>
> I use CCP4i, refmac5 for the refinement using data of 2.45
> angstrom. My R and Rfree is 0.182 and 0.267 respectively. For
> calculating Rfree ,5% of random data (1715 reflections) was
> used . So I see there is a difference of about 8.5% between R
> and Rfree. Is this difference reasonable ?
> Any idea how can I improve Rfree and difference between R and
> Rfree gets less than 5%.
> Thanks,
>
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