Refinement of macromolecular structures by the maximum-likelihood method

GN Murshudov, AA Vagin, EJ Dodson - … Crystallographica Section D …, 1997 - scripts.iucr.org
Acta Crystallographica Section D: Biological Crystallography, 1997scripts.iucr.org
This paper reviews the mathematical basis of maximum likelihood. The likelihood function
for macromolecular structures is extended to include prior phase information and
experimental standard uncertainties. The assumption that different parts of a structure might
have different errors is considered. A method for estimating σA usingfree'reflections is
described and its effects analysed. The derived equations have been implemented in the
program REFMAC. This has been tested on several proteins at different stages of refinement …
This paper reviews the mathematical basis of maximum likelihood. The likelihood function for macromolecular structures is extended to include prior phase information and experimental standard uncertainties. The assumption that different parts of a structure might have different errors is considered. A method for estimating σA using `free' reflections is described and its effects analysed. The derived equations have been implemented in the program REFMAC. This has been tested on several proteins at different stages of refinement (bacterial α-amylase, cytochrome c′, cross-linked insulin and oligopeptide binding protein). The results derived using the maximum-likelihood residual are consistently better than those obtained from least-squares refinement.
International Union of Crystallography