A multi-reservoir extruder for time-resolved serial protein crystallography and compound screening at X-ray free-electron lasers

Serial crystallography at X-ray free-electron lasers (XFELs) permits the determination of radiation-damage free static as well as time-resolved protein structures at room temperature. Efficient sample delivery is a key factor for such experiments. Here, we describe a multi-reservoir, high viscosity extruder as a step towards automation of sample delivery at XFELs. Compared to a standard single extruder, sample exchange time was halved and the workload of users was greatly reduced. In-built temperature control of samples facilitated optimal extrusion and supported sample stability. After commissioning the device with lysozyme crystals, we collected time-resolved data using crystals of a membrane-bound, light-driven sodium pump. Static data were also collected from the soluble protein tubulin that was soaked with a series of small molecule drugs. Using these data, we identify low occupancy (as little as 30%) ligands using a minimal amount of data from a serial crystallography experiment, a result that could be exploited for structure-based drug design. Protein serial crystallography at X-ray free-electron lasers (XFELs) is a powerful technique for structure determination. Here, authors present a device for sample delivery designed to abate challenges to non-specialists allowing for compound screening.

Automated summary

This study presents a new device for sample delivery at X-ray free-electron lasers (XFELs), which significantly reduces sample exchange time and user workload. The device was used to study protein structures and identified low occupancy ligands, which can be valuable for drug design.