Upgraded SSRF BL19U2 beamline for small-angle X-ray scattering of biological macromolecules in solution

The biological small-angle X-ray scattering (BioSAXS) beamline (BL19U2) at the Shanghai Synchrotron Radiation Facility, China, is dedicated exclusively to small-angle scattering experiments for biological macromolecules in solution. With recent advances in data-analysis algorithms and X-ray detectors, SAXS becomes an ideal complementary technique to other structural and biophysical methods, but it can also be applied alone to obtain important structural information. Owing to the increasing interest in solution scattering studies from the biological community, the workload on BL19U2 has steadily risen. A major upgrade of BL19U2 was performed to improve the beamline data quality, to enrich the possible sample environments and to provide a user-friendly interface. These upgrades involved the major components of BL19U2, including the optical system (slits, beamstop), the electronics, the control and acquisition software, and the sample environments, which resulted in improvements to the collected angular range in BL19U2. These upgrades have significantly broadened the scope of macromolecule size (from kilodaltons to gigadaltons) analysed at the beamline. The dedicated BL19U2 BioSAXS beamline now offers fully automated data-collection and remote-control possibilities. These developments have paved the way for high-throughput studies that generate significant quantities of structure information over a short period of time.