W0312

Rotating Anode Micro Focus Application for Protein Data Collection. Frank van Meurs, Anita Coetzee, Bram Schierbeek and Léon Seijbel, Bruker Nonius BV, Oostsingel 209, 2612 HL Delft, The Netherlands.

Systems including rotating anode sources with a 300 micron focal size have been predominantly used for single crystal X-ray data collection on proteins in the home labs. Micro focus generators have hardly been used there so far. These smaller focal sizes are certainly of interest when using them in combination with modern optics. Such combinations deliver a beam, which is not simply a plateau of radiation, but rather a centrosymmetric and inhomogenous beam. Modern data processing and correction software allows for appropriate correction of the observed intensities.

For small crystals of proteins a micro focus generator equipped with graded multi-layer optics offers a tremendous advantage in terms of I/sigma(I) and/or the number of observed reflections above a chosen threshold value. The smaller the sample the higher the gain with respect to the traditional plateau type of primary beam.

We will present results illustrating the gain observed for some typical small to medium sized protein samples of various crystal sizes.