LADI-III - A quasi-Laue diffractometer for biology

LADI-III is a quasi-Laue neutron diffractometer used for single-crystal studies of biological macromolecules at high resolution (1.5 - 2.5Å) in order to locate individual protons or deuterons of special interest, water structures or other small molecules that can be marked with deuterium to be particularly visible. Data collection is feasible for samples with unit-cell edges ranging from 50 to 150Å using crystal volumes from ~0.05 to 0.5mm³, respectively.

Neutron protein crystallographic projects typically aim to address questions concerning:

• enzyme mechanisms
• drug or ligand-binding interactions

LADI-III uses a large cylindrical area detector composed of neutron-sensitive image-plates, which completely surround the crystal and allows large numbers of reflections to be recorded simultaneously. Data are collected using a quasi-Laue method in order to provide a rapid survey of reciprocal space, while reducing the background on the detector compared to use of the full white beam.