Index

Protein Data Bank exchange dictionary (pdbx) version 1.0521

_pdbx_refine_component.correlation

Definition:

   
      Correlation coefficient of electron density for each residue or ligand, 
      side chain, main chain
 
      The density correlation coefficient is calculated for each component
      from atomic densities of (2Fobs-Fcalc) map - "Robs" and the model
      map (Fcalc) - "Rcalc" :
 
      D_corr =  <Robs><Rcalc>/sqrt(<Robs**2><Rcalc**2>)
 
      where <Robs> is the mean of "observed" densities of atoms of the
       component (backbone or side chain).
  
            <Rcalc> is the mean of "calculated" densities of 
             component atoms.
 
      The value of density for some atom from map R(x) is:
 
               sum_i ( R(xi) * Ratom(xi - xa) )
      Dens =  ---------------------------------- 
                   sum_i ( Ratom(xi - xa) ) 
 
        where  Ratom(x) is atomic electron density for the x-th grid point.
               xa - vector of the centre of atom.
               xi - vector of the i-th point of grid.
               Sum is taken over all grid points which have distance
               from the center of the atom less than the Radius_limit.
               For all atoms Radius_limit = 2.5 A.

      Ref: Vaguine, A.A., Richelle, J. & Wodak, S.J. (1999). Acta Cryst. D55,199-205

Type: float

Mandatory item: no

Category: pdbx_refine_component