This topic has been discussing on the BB many times and a little searching should give you some long-winded answers (some written by me).
The short version. If you refine a model with a common B factor for all atoms, or keep a very narrow distribution of B's, you will end up with an average B close to the Wilson B. If you don't something is seriously wrong. If you allow a distribution of B's in your model, that distribution is skewed on the high side because B factors cannot go below zero but there is no physical upper bound. The average of those B's will always be larger than the Wilson B. How much larger depends on your refinement method more than the properties of the crystal since it is determined by how large a tail you allow your B distribution to have. You didn't say what your B factor model was when you achieved an average value of 31 A^2. This value seems tiny to me since it implies that your intensities are falling off in resolution so slowly that you surely should have been able to measure data to a higher resolution. If you decide to deposit this model you should look into why you have such a low value. On the other hand, the average B of 157 A^2 seems quite reasonable for a 3 A model (using modern resolution cutoff criteria). It is higher than your Wilson B, but that is expected. In addition, as you note, the uncertainty of a Wilson B is quite large in the absence of high resolution data. Yes, this is the short version. ;-) Dale Tronrud On 4/7/2020 5:16 AM, Nicholas Keep wrote: > I am at the point of depositing a low resolution (3.15 A) structure > refined with REFMAC. The average B factors were 31 before I added the > TLS contribution as required for deposition which raised them to 157- > this is flagged as a problem with the deposition, although this did not > stop submssion. The estimated Wilson B factor is 80.5 (although that > will be quite uncertain) so somewhere between these two extremes. > > Is it only the relative B factors of the chains that is at all > informative? Should I report the rather low values without TLS > contribution or the rather high ones in any "Table 1"? Comments > appreciated. > > Thanks > > Nick > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
