Data Item _pdbx_refine_component.correlation


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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

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