Hi Raja,
I would like to add to Pavel's excellent advice and ask if you have tried TLS refinement? It always improves the model in our hands, and in most structures ( http://journals.iucr.org/j/issues/2009/03/00/he5437/index.html ). You might also consider excluding the regions with poor geometry from the NCS groups, to see if they are in fact different. You are also forcing NCS regardless of the RMS distance. I would refine a few rounds without NCS and with the default refinement parameters, and then then turn the NCS back on. Look in the .geo file for excessive distances, and examine these regions in Coot using the NCS ghosts and maps to decide if they should be excluded from the NCS groups.
Another suggestion would be to try the kicked maps, or generate composite omit maps to look at the regions with poor geometry.
You might need to subtly change half a dozen residues surrounding the geometry outlier to fix the problem. This might be done with simulated annealing, or try autobuild in place.
Lastly, if its only a few residues, you can't fix it, and the maps support your model, don't worry about it.
Best Regards,
Kendall Nettles
On 11/17/09 3:02 PM, "Raja Dey"
Hi Raja,
pdb validation summary letter gives a list
of covalent bond angles greater than 6 times standard deviation for dna part of my molecule. I am wondering if someone can tell how to fix that. I used PHENIX to refine my molecule. I did not use any restraints for the dna part.
did you completely turn off all the geometry restraints for that selected part of your structure? If so, then it is not surprising that it got distorted during refinement at 2.9A resolution, and therefore I would suggest re-running phenix.refine using all the restraints that phenix.refine normally uses by default.
Also a few amino acids are listed for which
phy and psy fall outside Ramachandran plot. I like to know what is the best way to fix these phy, psy angles.
1) Can't you do it in Coot? (especially when there are only a few such outliers, as you say).
2) Try adding riding H atoms and re-run phenix.refine (with and w/o weights optimization to see which option gives better results).
3) Try a quick geometry regularization going into trying "2)". Repeat the same with and w/o H.
This is a pretty frequent question, so I hope someone someone can tell a success story about it...
Final refined parameters are
REMARK Start: r_work = 0.3576 r_free = 0.3345 bonds = 0.009 angles = 1.344 REMARK Final: r_work = 0.2517 r_free = 0.2845 bonds = 0.008 angles = 1.209
at 2.9A resolution
Looks reasonable given the resolution...
Pavel.
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