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Re: [ccp4bb]: removeing ncs



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hi !

Firstly, it may be good idea to consider the data/parameter ratio in your
structure.  If its of fairly good resolution (say 2.2A or better), you may
have the ratio above 1.2-1.5  Then you may consider to remove NCS
restraints. In that case, you can monitor R-free for different weights and
also for "zero" weights (i.e. for no restraints) and see if it turns out
to be a better R-free in no restraints case.  Further, you may check the
validity of NCS related monomers using LSQMAN program from Upasala
Software Factory

There are atleast 2 articles in lit. which might be of some help for you
to decide.

1. Kleywegt GJ
   Use of NCS in crystallographic refinement
   Acta Cryst D 52 pp : 842

2. Kleywegt GJ, Brunger AT.
   Checking your imagination: applications of the free R value.
   Structure. 1996 4 pp:897-904.

Hope it helps,
Anil

  _____________________________________________________________________
   Anil K Padyana, Department of Physics, Indian Institute of Science,
   Bangalore - 560 012, INDIA Phone:+91-80-3092718 FAX:+91-80-3601683
  _____________________________________________________________________




On Tue, 26 Sep 2000, Leonard Thomas wrote:

> ***  For details on how to be removed from this list visit the  ***
> ***    CCP4 home page http://www.dl.ac.uk/CCP/CCP4/main.html    ***
> 
> Hi all,
> 
> Just a simiple (I think) question about using NCS restraints.  I have a
> structure that has 2 mol/asymm.  I have been using NCS retraints sofar
> with  pretty good results.  My question is when do most people remove
> the restraints, if they are removed at all. The compound is not a dimer
> so there must be some difference in the molecules.
> 
> Thank you for your comments.
> Len
>   
> -- 
> Leonard M. Thomas Ph.D.			Phone (816)235-2571
> University of Missouri - Kansas City	Fax   (816)235-1503 
> School of Biological Sciences		email thomasle@umkc.edu
> 5100 Rockhill Road, Kansas City, MO 64110
> 

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