You dont say what the translation vector is, or the spacegroup, but if
one of the translation components is fractional, eg 0.5 with an
orthogonal SG or 0.333 in a trigonal, then it can generate aparent
absences along an axis, and it s easy to mis-assign the spacegroup; eg
call something P212121 when in fact it is P21 2 21 or some such..
The effect of that is just what you describe..
Eleanor
Marina Siponen wrote:
Dear CCP4 bulletin boarders,
I've been experiencing problems with the refinement of a structure at a
resolution of 1.9 Å with a ~30% pseudo-translation.
The structure in question is a dimer of dimers (i.e. tetramer.) This is
what is observed in the asu and is correct based on biological
information. During refinement one of the two dimers refines nicely
while the second is seeing its B-factors rise considerably > 70 or 80,
consequently maps are degrading while R-factors are steadily decreasing.
Any explanation/suggestions/experience dealing with pseudo-translation
in data processing/solving and refinement would be particularly helpful.
Any good literature dealing with the subject would also be greatly
appreciated.
Thank you
Marina
Marina Siponen, PhD
Karolinska Institutet
MBB/SGC
Scheeles väg 2
171 77 Stockholm
Sweden
Phone: +46-8-524 868 42
Fax: +46-8-524 868 68
[email protected]
