Dear Faisal, The Wilson B-factor is the B-factor of the diffraction data and is calculated by the data processing software. The B-factor of the atoms is produced by the refinement program. Ideally the Wilson B (B-factor of the data) and average B of all atoms (B-factor of the model) should be very similar.
In a perfect world, your resolution limit is determined by the Wilson B-factor (amount of crystal disorder) and one expects a low Wilson B-factor for high resolution data and a high Wilson B-factor for low resolution data. I think there are even papers were people have calculated the relation between Wilson B-factor and resolution limit. In practice, for low-resolution data the calculated B-factor may not be very well defined since it also depends on the scale factor. Also for high-resolution models, many water molecules with high B-factors may be included, while for low-resolution models only a few waters with low B-factors may have been included skewing the calculated average B. The first thing to check would be the Wilson B-factors and that they do not deviate too much from the average B-factors. I would be cautious drawing too many conclusions from the average B-values, since they reflect the crystal quality. E.g. if the cryoprotectant for one of the crystals was not optimal, you may get a high average B-value which has nothing to do with the stability of your protein. Best, Herman Von: CCP4 bulletin board [mailto:[email protected]] Im Auftrag von Faisal Tarique Gesendet: Donnerstag, 14. August 2014 10:31 An: [email protected] Betreff: [ccp4bb] Difference between different b factors values Dear all I request you to please tell me the difference between wilson B-factor and average B, all atoms ?? I have two structures one native at 2A resolution, having mean b factor of 24 and the other a complex structure of the same protein with a ligand (at 2.6A resolution) has mean b factor of 23..Why there is a difference in the b factor for these two coordinates with the later having (low resolution) lower value than the previous (high resolution)..?? is this a normal phenomenon or the stability is due to bound ligand molecule, which is stabilizing the whole structure ?? Please pour some light in this direction.. -- Regards Faisal School of Life Sciences JNU
