[ccp4bb]: Refinement: R factor not going down.

["Inna Levin" <inna.levin@weizmann.ac.il>]

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Do you apply NCS (non crystallographic symmetry) restraints/constraints? 
If yes, it might be that some parts of your molecule donâ€*t comply with it. In such case a non-averaged omit map should help. 
(In my case NCS could be applied everywhere, but at one single loop, and R-factor did not go beyond 0.35, unless the NCS was released)

Inna Levin
-----------------------------------------------------


Hello! Is there anyone who can give me some help?

I am working on a protein structure and get in trouble in refinement. Some details are:
(1)SG: p212121
(2)diffraction data: 
       completeness: >95 (outmost > 85)
       resolution: 2A (I/sigma>>3, completeness>85)
       R_merge: total 0.06, outmost shell 0.124
(3)molecular replacement, sequence homology between model and my molecule > 80
I have tried several times of refinement. Every time I can only refine to R=0.3 and cannot go any more. Now the detail
is:
       I have done: rigid refinement, anneal, minimize refinement, B_group refinement and manual adjustment of the
model
       R=0.30  R_free=0.31
       composite_omit_map fit my model quite well
       cannot reduce R or R_free if apply minimize, b_individual or add_water.
       I use cns on Linux (Athlon 2000+ SMP)

What's wrong with my work? Thank you for any help in advance!
         
                               

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