LAUE IMAGE-ANALYSIS .2. VARIABLE RADIAL ELLIPTIC MASKING AND ITS APPLICATION IN STUDIES INVOLVING INHERENTLY STREAKED LAUE EXPOSURES

Many Laue diffraction patterns from crystals of particular biological or chemical interest are of insufficient quality for their analysis to be feasible. In many cases, this is because of pronounced streaking of the spots owing to either large mosaic spread or disorder introduced during reactions in the crystal. Methods for the analysis of exposures exhibiting radial or near-radial streaking are described, along with their application in Laue diffraction studies of form-II crystals of Met-tRNA synthetase and a photosynthetic reaction centre from Rhodobacter sphaeroides. In both cases, variable elliptical radial masking has led to significant improvements in data quality and quantity and exposures that previously were too streaked to process may now be analysed. These masks can also provide circular profiles as a special case for processing high-quality Laue exposures and spatial-overlap deconvolution may be performed using the elliptical or circular masks.