-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Dear Nicholas,
for a data set with 5132 unique reflections you should flag 10.5% for Rfree, otherwise you could as well drop Rfree completely and use the whole data set for refinement. At least this is how I understand Axel Brunger's article about Rfree where he states that one needs 500-1000 reflections for a significant meaning of Rfree. I have wondered where the '5%-rule' came in which compromises the Rfree for low resolution data sets (especially with high symmetry). If Axel Brunger's initial statement has become obsolete I would appreciate some clarification on the required number of flagged reflection, but until then I will keep on flagging 500-1000 reflections, rather than 5%. Tim On 10/15/2011 10:48 AM, Nicholas M Glykos wrote: >>> For structures with a small number of reflections, the statistical >>> noise in the 5% sets can be very significant indeed. We have seen >>> differences between Rfree values obtained from different sets reaching >>> up to 4%. >> >> This is very intriguing indeed! Is there something specific in these >> structures that Rfree differences depending on the set used reach 4%? >> NCS? Or the 5% set having less than ~1000-1500 reflections? > > Tassos, by your standards, these structures should have been described as > 'tiny' and not small ... ;-) [Yes, significantly less than 1000. In one > case the _total_ number of reflections was 5132 reflections (which were, > nevertheless, slowly and meticulously measured by a CAD4 one-by-one. These > were the days ... :-)) ]. > > > > - -- - -- Dr Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen GPG Key ID = A46BEE1A -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iD8DBQFOm9p6UxlJ7aRr7hoRAkumAKD5beU+JnpRuO7TJF1232a1axMtAACdHCI5 nf8+rtr5Are0kBgmk9w0rg4= =Agc9 -----END PGP SIGNATURE-----
