Neutron Laue diffraction in macromolecular crystallography

The time scales required for conventional neutron diffraction analysis of biological single crystals at, or near, atomic resolution are prohibitive such studies are rarely performed. Laue (white beam) diffraction can provide a more rapid and efficient survey of reciprocal space, maximising the flux at the sample and stimulating large numbers of reflections simultaneously. A LAue Diffractometer (LADI). designed specifically for macromolecular crystallography, has been installed on a cold neutron guide at ILL. The detector comprises a large Gd₂O₃-doped neutron-sensitive image plate (400 × 800 mm) mounted on a cylindrical camera (318 mm diameter) that is read in phonographic mode after exposure. Detector response has been evaluated and performance indicators are given. Narrow (Quasi-Laue) band-passes (dλ/λ = 8-20%) are often required for large unit-cell biological crystals in order to reduce reflection overlap and incoherent background. Laue and Quasi-Laue data have now been collected for a number of proteins and other biological crystals. Recent results are presented and future prospects reviewed.