DALI - A quasi-Laue diffractometer for large proteins

To extend the capabilities and capacity for neutron macromolecular crystallography experiments at ILL, a second quasi-Laue diffractometer DALI has been commissioned at H141 as part of the ILL Endurance Programme. DALI utilizes a neutron velocity selector to provide both higher transmission and a narrower bandwidth (δλ/λ ~10%) than LADI-III, required to extend capabilities to studies of larger, more complex systems.

In October 2025, a completely new neutron-sensitive cylindrical image plate detector was built and installed on DALI and neutron diffraction tests and analyses were performed using crystals of proteins covering a wide range of molecular weights, from the very small (6 kDa) to the very large (271 kDa). The results show that the LADI-III and DALI neutron protein crystallography diffractometers are highly complementary; LADI-III delivers higher quality diffraction data for small to medium-sized proteins (5-70 kDa) and DALI, with its new detector and narrow bandwidth velocity selector, now delivers diffraction data of higher quality for large proteins (70-150 kDa). In addition, the tests indicate that DALI can even be used to study very large proteins (>150 kDa) that were previously out of range. This represents a step change in capabilities for neutron protein crystallography research and further cements the ILL’s position as world-leading in the field.