Low B-factors

[F.E.Dodd]

Hi,

I am currently refining a structure with 8 to 3A data.

I have processed the data using CCP4 and get a B-factor for the
data between 15 and 20 from "truncate", depending on the resolution 
ranges I use.

After one simulated annealing run, which yielded a R-work of 24%
and an R-free of 30%, I tried to do an overall B-factor refinement.
(i.e. one B-factor for the whole molecule)  Xplor refines the 
B-factor down to 2 and the says that it has converged.  

Can anyone tell me why I might be getting such a low B-factor
in the refinement and how I might go about spolving the problem?

Thanks,
Fraser.


-- 
 Fraser E. Dodd,
 CCLRC Daresbury Laboratory,     Telephone: +44 (0)1925 603625
 Daresbury, Warrington,                Fax: +44 (0)1925 603124
 Cheshire, WA4 4AD,
 U.K.                                E-mail: F.E.Dodd at dl.ac.uk
--