In this Bruker Webinar, Dr. Andrea Thorn from the Laboratory of Molecular Biology in Cambridge presents the new program AnoDe for macromolecular crystallography.

AnoDe is part of the SHELX software suite. The program estimates anomalous or heavy-atom density by reversing the usual procedure for experimental phase determination by the SAD, MAD, SIRAS and other methods. Instead of adding a phase shift alpha to the heavy atom phases to obtain a starting value for the native protein phase, the phase shift is subtracted from the native phase to obtain the heavy atom substructure phase. The required native phase is calculated from the information in a PDB file of the structure.

The resulting density enables even very weak anomalous scatterers such as sulfur to be located, to visualize radiation damage in crystal structures and differences between isomorphous crystals. Potential applications include the identification of unknown atoms and the validation of molecular replacement solutions.

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