Mosaic spread characterization of microgravity-grown tetragonal lysozyme single crystals

Mosaic spread values for crystals grown in microgravity were measured using synchrotron radiation. Full width at half maximum (FWHM) values for diffra ction line profiles in the range 10-20 " (arc seconds, 1 " = 1 degrees/3600 ) were observed. These values are similar to these measured for crystals gr own on earth using the gel-acupuncture method. The crystals analysed are co mposed of from two to five domains producing peaks having widths from 5 to 15 ". The distribution of these domains is neither homogeneous (with domain s of lower quality concentrated in the centre of the crystal) nor isotropic (producing peaks whose width changes depending on the observation directio n). Methodological aspects are also discussed, with special consideration o f the effects of mosaic spread on the data-collection procedures for high-r esolution (low-intensity) reflections.