A BAYESIAN-APPROACH TO LAUE DIFFRACTION ANALYSIS AND ITS POTENTIAL FOR TIME-RESOLVED PROTEIN CRYSTALLOGRAPHY

A solution to the energy-overlap problem in Laue diffraction is descri bed that does not require redundancy in the measurements. The new meth od follows a Bayesian approach with multidimensional probability densi ty functions. The only assumption made is the validity of Wilson stati stics. The intensity components of reflection multiplets are deconvolu ted and estimates of their precision are obtained. The Laue patterns a re processed to their physically relevant wavelength-dependent resolut ion limit; no 'soft parameters' are involved. The Bayesian method may also be applied to deconvoluting spatial overlaps. The power of the me thod is demonstrated by a test application to bovine trypsin. The comp leteness at low and medium resolution as well as at very high resoluti on (1.4 Angstrom) is enhanced very substantially as compared with stan dard procedures; the 'low-resolution hole' problem is solved. As a con sequence, the contrast in electron-density maps improves so far that t hey become comparable in quality with maps from monochromatic data at high resolution. The new method is of interest for all types of Laue d iffraction experiments, in particular for single-shot time-resolved st udies on short time scales. Simulation calculations for single-shot La ue conditions and for the disorder-order transition in trypsinogen as a model system demonstrate the potential power of applications in prot ein crystallography that combine high resolution and Bayesian processi ng.