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

[Phil Evans <pre@mrc-lmb.cam.ac.uk>]

***  For details on how to be removed from this list visit the  ***
***          CCP4 home page http://www.ccp4.ac.uk         ***



At 2A resolution (or better) arp/warp (warpNtrace) is a good method of
getting away from bias problems in molecular replacement

Phil


OnLineHelpForm writes:

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!