Speaker
Dr
Esko Oksanen
(European Spallation Source ESS AB)
Description
The NMX macromolecular diffractometer planned at the European Spallation Source in Lund is a time-of-flight (TOF) quasi-Laue diffractometer optimised for small samples and large unit cells in order to locate the hydrogen atoms relevant for the function macromolecules.
The ESS long pulse source with its highly brilliant neutron moderator is ideally suited for a macromolecular diffractometer. We estimate that a macromolecular diffractometer at the ESS could be used to collect data from crystals of ~200 µm dimension in some days, which represents an order of magnitude improvement over currently available sources. More importantly it broadens the range of systems that can be investigated to many biologically very interesting molecules, including membrane proteins such as proton pumps.
One of the limiting factors with current neutron instruments is that the fixed detector geometry only allows a maximal unit cell edge of ~150 Å to be resolved without a compromise in the diffraction resolution (dmin). The NMX detectors will be mounted on robotic arms, allowing larger unit cells to be resolved by increasing the crystal-to-detector distance. This incurs an increase in the data collection time, but reflections to the same dmin can still be observed by moving the detectors. Many of the scientifically most interesting systems, such as proton pumping membrane proteins, crystallise in large unit cells, so being able to resolve a large unit cell edge is a unique advantage. The combination of a neutron flux higher than leading high flux reactor instruments, such as LADI-III, together with the ability to resolve large unit cells and the ability to separate signal from background by time-of-flight leads to world-leading performance particularly with the experimentally most challenging systems. This would transform neutron crystallography into a technique that could answer a significantly larger number of hydrogen related questions in biomolecular science than before.
Primary author
Dr
Esko Oksanen
(European Spallation Source ESS AB)
Co-author
Giuseppe Aprigliano
(European Spallation Source ESS AB)
