LADI—A dedicated facility for biological crystallography

The LAD1 instrument at ILL provides a unique and powerful tacility for neutron protein crysrdlography at high-resolution (l.5Å) and is used to locate hydrogen atoms and water molecules thatcannot be seen by X-ray analysis alone in biological structures [1]. The combination of a broad bandpass quasi-Laue geometry with a large cylindrical area detector provides 10–100 fold gains in efficiency compared with conventional neutron diffractometers [2]. This has made feasible studiesof larger biological complexes and smaller crystals than previously possible and has redefined the role and expectations of neutron protein crystallography [3,4]. Current studies are addressing questions of broad biological significance concerning enzymatic mechanism, ligand-binding interactions, solvent effects, structure dynamics and their implications [5-l0]. Life scientists are nowpresenting state of the art problems in biology that challenge the current capabilities of the insnument and a further order of magrutude gain in performance would be decisive in opening new fields of research. The developments of the instrument proposed to the ILL millennium program will provide unprecedented capability for neutron analysis of biological macromolecules such as proteins and DNA/RNA, and become the benchmark for biomolecular crystallography at the next generation neutron sources.