PROTEIN CRYSTALLOGRAPHY AT ULTRA-SHORT WAVELENGTHS - FEASIBILITY STUDY OF ANOMALOUS-DISPERSION EXPERIMENTS AT THE XENON K-EDGE

A protein crystallography experiment at the xenon K-edge (lambda = 0.3 58 Angstrom) has been successfully carried out at the materials scienc e beamline (BL2/ID11) of the ESRF. The samples used in this methodolog ical study were crystals of porcine pancreatic elastase, a 26 kDa prot ein of known structure. The diffraction data are of excellent quality. The combination of isomorphous replacement and anomalous dispersion o f a single xenon heavy-atom derivative allowed accurate phase determin ation and the computation of a high-quality electron density map of th e protein molecule. This is the first fully documented report on a com plete protein crystallography experiment, from data collection up to p hase determination and calculation of an electron density map, carried out with data obtained at ultra-short wavelengths. Experimental consi derations as well as possible advantages and drawbacks of protein crys tallography at very short and ultra-short wavelengths are discussed.