[ccp4bb]: End of Refinement ?

[raji <raji@lamar.colostate.edu>]

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Hi Everyone,
I am trying to understand when one 'practically' decides to end structure 
refinement.
In my case, I am working on a 2A structure and I am at a stage where I have 
added protein, DNA, ligand, waters and alternate side chains (and I think I 
can still continue to add waters!). 
I have a few questions-
1. I added alternate side chains in my previous round of refinement (374 atoms 
out a total of 13770 atoms) and I saw absolutely no change in either my 
R-factor or R-free. (I did not add much else to my structure apart from the 
side chains). Does that mean they make no difference to my structure inspite 
of the clear density that I see ?
2. Is plateauing of R-free the criterion to stop refinement ?
3. Is there a quick way to guesstimate how many atoms it takes to bring about, 
for e.g., a 1% drop in R-free. I ask this because in my past few rounds, there 
has been only a marginal drop in R-free after manual addition of a couple 
hundred water molecules.
Pl. help me understand. 
Thanks for your time and patience.
Raji

Rajeswari Edayathumangalam
Dept. of Biochemistry & Molecular Biology
Colorado State University
Fort Collins, CO 80523 USA