The NMX macromolecular diffarctometer is a time-of-flight (TOF) quasi-Laue diffractometer optimised for small samples and large unit cells. The ESS long pulse source is well suited for a quasi-Laue macromolecular diffractometer that can spread the background in the TOF dimension, while the Bragg peaks are observed at a defined TOF. Therefore a macromolecular diffractometer at the ESS can be used either to study systems with smaller crystals or larger unit cell volumes. Growing well-ordered protein crystals of cubic millimetre volume is extremely difficult, so the instrument is optimised for submillimeter crystal sizes. The small, low-divergence beam leads to a high transverse q-resolution, which makes the instrument useful for a wide range of single crystal diffraction experiments in materials science and magnetism.
Detectors mounted on robotic arms allow large unit cells to beresolved by increasing the crystal-to-detector distance, which incurs an increase in the data collection time, but without a compromise in dmin. Many of the scientifically most interesting biological systems, such as proton pumping membrane proteins, crystallise in large unit cells, so resolving a large unit cell edge is a unique advantage. Materials science or magnetism experiments often require bulky sample environment, around which the robotic positioners can place the detectors in an optimal manner.
The combination of a neutron flux comparable to leading high flux reactor instruments, together with time-of-flight to separate signal from background, the ability to resolve large unit cells leads to world-leading performance particularly with the experimentally most challenging systems. This would transform neutron macromolecular crystallograhphy into a technique that could answer a significantly larger number of hydrogen-related questions in biomolecular science than before.
The preliminary engineering design was completed in 2014 culminating with the successful Tollgate 2 review in December 2014. The team are currently implementing the recommendations of the review in preparation for the detailed engineering design.
Instrument Core Team
Scientific Project Leader Esko Oksanen, ESS
Lead Engineer Giuseppe Aprigliano, ESS
Institut de Biologie Structurale, Grenoble, France
Department of Molecular Biology and Genetics, University of Aarhus, Denmark