Towards automated Laue data processing: application to the choice of optimal X-ray spectrum

Laue data reduction has now reached a level of sophistication that allows n early automated processing to be performed. The software described enables complete reduction of the data with essentially no user intervention, makin g Laue processing almost as straightforward as monochromatic data processin g. Interactive work is limited to the indexing of only one Laue pattern. Mo re importantly, it is shown that the data quality is substantially enhanced when soft-limited predictions are used. Further improvement obtained by ta king advantage of the structure-factor amplitudes from a known closely rela ted structure is described. To determine the most suitable type of insertio n device to be used for time-resolved Laue crystallography, the technique d escribed was applied to Laue data sets collected from photoactive yellow pr otein under identical conditions but with three different insertion devices : a wiggler, a broad-bandpass undulator and a single-line undulator. Althou gh the optimal choice may ultimately be dictated by sample parameters (such as mosaic spread) and by the type of experiment (repeatable or non-repeata ble reactions), the results here show that the use of single-line undulator s will generally yield by far the best compromise between data quality, acq uisition time and radiation damage.