[ccp4bb] unusually low B-factors

[Paul Paukstelis]

Greetings,

We've been working on a number of related structures. Crystals are in 
P64 with fairly small unit cell (40,40,55) and only diffract to around 
2.5-3.0, so we aren't working with a lot of reflections. For several of 
these data sets the maps look very reasonable but Refmac refinement 
gives us unusually low B-factors after either individual or grouped 
refinement (average of around 10 A2 with some residues around 2 A2) 
while others are more 'normal' (avg. 30-40) with very similar maps. I 
suspect something in data processing, but I was wondering if there are 
opinions about what I should look for in cases like this. Thanks in advance.

--paul