Data Item _refine.overall_SU_ML


Item name
Category name
Attribute name
Required in PDB entries
Used in current PDB entries
Yes, in about 46.4 % of entries

Item Description

The overall standard uncertainty (estimated standard deviation) of the positional parameters based on a maximum likelihood residual. The overall standard uncertainty (sigmaX)2 gives an idea of the uncertainty in the position of averagely defined atoms (atoms with B values equal to average B value) 3 Na (sigmaX)2 = --------------------------------------------------------- 8 pi2 sumi {[1/Sigma - (Eo)2 (1-m2)](SUM_AS)s2} Na = number of atoms Eo = normalized structure factors m = figure of merit of phases of reflections included in the summation s = reciprocal-space vector SUM_AS = (sigmaA)2/Sigma2 Sigma = (sigma{E;exp})2 + epsilon [1-(sigmaA)2] sigma{E;exp} = experimental uncertainties of normalized structure factors sigmaA = <cos 2 pi s deltax> SQRT(SigmaP/SigmaN) estimated using maximum likelihood SigmaP = sum{atoms in model} f2 SigmaN = sum{atoms in crystal} f2 f = atom form factor deltax = expected error epsilon = multiplicity of diffracting plane summation is over all reflections included in refinement Ref: (sigma_A estimation) "Refinement of macromolecular structures by the maximum-likelihood method", Murshudov, G. N., Vagin, A. A. & Dodson, E. J. (1997). Acta Cryst. D53, 240-255. (SU ML estimation) Murshudov, G. N. & Dodson, E. J. (1997). Simplified error estimation a la Cruickshank in macromolecular crystallography. CCP4 Newsletter on Protein Crystallography, No. 33, January 1997, pp. 31-39.

Data Type

Data type code
Data type detail
float item types are the subset of numbers that are the floating numbers.
Primitive data type code
Regular expression