title: How good are my data and what is the resolution?
abstract: Following integration of the observed diffraction spots, the process of `data reduction' initially aims to determine the point-group symmetry of the data and the likely space group. This can be performed with the program POINTLESS. The scaling program then puts all the measurements on a common scale, averages measurements of symmetry-related reflections (using the symmetry determined previously) and produces many statistics that provide the first important measures of data quality. A new scaling program, AIMLESS, implements scaling models similar to those in SCALA but adds some additional analyses. From the analyses, a number of decisions can be made about the quality of the data and whether some measurements should be discarded. The effective `resolution' of a data set is a difficult and possibly contentious question (particularly with referees of papers) and this is discussed in the light of tests comparing the data-processing statistics with trials of refinement against observed and simulated data, and automated model-building and comparison of maps calculated with different resolution limits. These trials show that adding weak high-resolution data beyond the commonly used limits may make some improvement and does no harm.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, England. pre@mrc-lmb.cam.ac.uk
authors.forename: Philip R
authors.initials: PR
authors.lastname: Evans
authors.forename: Garib N
authors.initials: GN
authors.lastname: Murshudov
mesh_terms: D000465:Algorithms; D016880:Anisotropy; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D003627:Data Interpretation, Statistical; D007090:Image Interpretation, Computer-Assisted; D008958:Models, Molecular; D012984:Software
keywords: data reduction; data scaling; data statistics; software