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Dear all,
I am refining a structure with two
protomers in the asymmetric unit; resolution range 25-2.0 Angstroem; hexagonal
space group P6122; total number of reflections: 22 000; total number of atoms to
refine: ~2800.
I have been using TLS refinement in
the last stage of refinement and got a nice drop in Rfree and Rcryst: before
TLS: Rfree=19.3 Rcryst=17.3. after TLS refinement: Rfree=18.2 Rcryst=16.6.
I used two TLS groups for the two protomers in
the asymmetic unit respectively, 5 cycles of TLS refinement+9 cycles of
normal Refmac refinement. However I did not turn the "Fix B-factors" field on,
though I entered Wilson B in the respective field. When going back and runnning
the same refinement procedure as above, this time fixing B-factors to Wilson B I
get: Rfree=18.5 Rcryst= 17.3. i.e little worse than above.
Since I am not very experienced in
using TLS refinement my question is whether it is necessary to fix the
B-factors. It makes more sense to me, but I would like to have some competent
advice on that. If fixing is advicable: to what should I fix it (with this
particular refinement problem).
Thanks very much,
Florian
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Florian Schmitzberger University of Cambridge Department of Biochemistry 80 Tennis Court Road CB2 1GA Cambridge Tel: 0044-1223-766029 |