[phenixbb] refinement question

Francis E Reyes Francis.Reyes at Colorado.EDU
Fri Jun 26 08:59:30 PDT 2009

NCS restraints increases the data:parameter ratio in low resolution  
situations. Others have suggested not releasing NCS restraints unless  
your resolution is > 2.0A and the model is complete (as including NCS  
can help you build/complete your model with the use of NCS averaged  
maps). When you do not include NCS, do you see sidechain differences  
among the monomers making up the NCS?

Personally I keep NCS in unless I do see genuine differences among the  
monomers (which could be biologically significant depending on your  
system). Of course these small differences (say in a binding pocket)  
would likely need to be verified with omit maps or even better,  

Just my 0.02.


On Jun 26, 2009, at 9:49 AM, Maia Cherney wrote:

> Hi all,
> I am wondering why the ncs refinement gives me a better Rfree (21.0%)
> than without ncs (21.7%). I have this experience with different  
> projects
> and different data  (3.3 A  and 2.3 A). The R work is similar ~18%
> As it's a fact with my data, which refinement do you think should be  
> the
> final?
> Maia
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Francis Reyes M.Sc.
215 UCB
University of Colorado at Boulder

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