Index

Protein Data Bank exchange dictionary (pdbx) version 1.0521

_phasing_MIR_der.R_cullis_anomalous

Definition:

   Residual factor R~cullis,ano~ for anomalous reflections for this
   derivative.

   The Cullis R factor was originally defined only for centric
   reflections.  It is, however, also a useful statistical
   measure for anomalous  reflections, which is how it is used in
   this data item.

   This is tabulated for acentric terms.  A value less than 1.0
   means there is some contribution to the phasing from the
   anomalous data.

                sum |Fph+~obs~Fph-~obs~ - Fh+~calc~ - Fh-~calc~|
            R~cullis,ano~ = ------------------------------------------------
                       sum|Fph+~obs~ - Fph-~obs~|

   Fph+~obs~  = the observed positive Friedel structure-factor
                amplitude for the derivative
   Fph-~obs~  = the observed negative Friedel structure-factor
                amplitude for the derivative

   Fh+~calc~  = the calculated positive Friedel structure-factor
                amplitude from the heavy-atom model
   Fh-~calc~  = the calculated negative Friedel structure-factor
                amplitude from the heavy-atom model

   sum is taken over the specified reflections

   Ref: Cullis, A. F., Muirhead, H., Perutz, M. F., Rossmann, M. G.
        & North, A. C. T. (1961). Proc. R. Soc.  London Ser. A,
        265, 15-38.

Type: float

Mandatory item: no

Category: phasing_MIR_der