An Algorithm for Automatic Mosaic Spread Analysis of a Protein Crystal

The present paper describes the program MOSAICITY which assembles tools developed for the mosaic spread analysis of protein crystals. This analysis, performed in an automatic and nonparametric way, combines wavelet filters and morphological treatment in order to localize reflections in a diffraction pattern. The reflection intensities, rescaled according to incidence-beam intensity and corrected for the background, are measured using a fine rotation angle slicing. A Gaussian profile fitting is performed. The angular width can be corrected for the Lorentz factor, beam divergence and energy resolution in order to obtain an estimate of the mosaic spread of the crystal. For this last stage, a new analytical expression for the φ extent of the reflection range has been derived.