title: Simple algorithm for a maximum-likelihood SAD function.
abstract: Recently, the multivariate complex normal distribution has been used to develop a maximum-likelihood probability function for single-wavelength anomalous diffraction phasing and refinement of heavy-atom parameters [Pannu & Read (2004), Acta Cryst. D60, 22-27]. The function accounts explicitly for the correlations between the observed and calculated Friedel mates and their errors. However, the method of derivation of the equation described by Pannu & Read (2004) leads to a complicated likelihood expression that suffers from a number of algorithmic limitations. Here, an alternative derivation of the P(SAD) function is described that leads to simplified algorithmic requirements and that allows an intuitive understanding of the expression.
authors.affiliation: University of Cambridge, Department of Haematology, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 2XY, England.
authors.forename: Airlie J
authors.initials: AJ
authors.lastname: McCoy
authors.forename: Laurent C
authors.initials: LC
authors.lastname: Storoni
authors.forename: Randy J
authors.initials: RJ
authors.lastname: Read
mesh_terms: D000465:Algorithms; D043542:DNA, Z-Form / Q000737:chemistry; D016013:Likelihood Functions
chemical_list: D043542:DNA, Z-Form