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Hi,<br>
<br>
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<div>I do have a data is at very low resolution, so only possible to
do rigid body refinement. <br>
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<br>
it depends what you call "low resolution". In small molecule
crystallography ~1A resolution is "low resolution" (Acta Cryst. (2007).
D63, 160-170). So, without knowing what the resolution of your data is
I can't really tell whether you need to refine individual anisotropic
B-factors or the whole model as just one TLS group.<br>
<br>
Anyway, if by "low resolution" you mean what comes to my mind this very
minute, you can still try:<br>
<br>
Coordinates:<br>
- Simulated Annealing refinement in torsion angle space;<br>
- Highly restrained refinement of individual coordinates;<br>
- Optimize weights against Rfree.<br>
- You may need to use secondary-structure restrains (available in
recent PHENIX versions).<br>
ADP:<br>
- combined refinement of TLS+individual or group B-factors;<br>
- Highly restrained individual ADP refinement;<br>
- Simple group ADP refinement (where the size of groups depends on
resolution or/and data-to-parameters ratio)<br>
- Optimize target weights.<br>
NCS:<br>
- use if available.<br>
Bulk-solvent:<br>
- optimize mask parameters (r_solvent and r_shrink) using
optimize_mask=true (this is will done automatically in future versions
of phenix.refine).<br>
Multi-Start SA:<br>
- people find it useful (Andrei Korostelev, Martin Laurberg, and Harry
F. Noller "Multistart simulated annealing refinement of the crystal
structure of the 70S ribosome". PNAS 2009 106:18195-18200).<br>
<br>
Good luck!<br>
Pavel.<br>
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