ncs-strict and waters

Gerard 'CD' Kleywegt GERARD at XRAY.BMC.UU.SE
Tue Feb 27 05:09:51 EST 1996


One for the FAQ ?

NCS strict = CONstrained -> all units are identical, including any water
  molecules etc.; the other molecules don't even "exist" during refinement;
  they are generated from the refined one plus the operators for
  structure-factor calculations -> no way to have differences

NCS REstraints -> some or all (parts of) molecules are similar; this means
  that water molecules can be omitted from the restraint scheme; to get
  very small differences (i.e., almost as small as with constraints) for
  the restrained parts, use force constants of the order of 100-300 kCal
  mol-1 A**-2 (this also tends to yield simlar Rfree values)

--gerard



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