Re: [ccp4bb]: removeing ncs

["David J. Schuller" <schuller@uci.edu>]

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On Tue, 26 Sep 2000, Leonard Thomas wrote:

> 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.

i might leave the restraints in place until i had reason to do
otherwise.  do you see any differences in the structures?  do you see any
evidence in the difference maps that one of the monomers wants to
move?  (e.g. positive fo-fc density on one side and negative on the other 
side of a loop)

you could also try halfway measures; reduce the weight on the restraints
or else reduce weight on the sidechains but not the mainchain. if a loop
clearly deviates from the NCS you could leave just that part out of the
restraints. 

how badly do you need the restraints?  if the resolution is ~ 2.5 A or
worse you may want to keep them around as long as possible.

=======================================================================
"I am an omnivorous reader with a strangely retentive memory for trifles"
                                                      -- Sherlock Holmes
=======================================================================
                        David J. Schuller
                        modern man in a post-modern world
                        University of California-Irvine
                        schuller@uci.edu