The SSRL Beamline BL4-2 is a permanent experimental station for small-angle X-ray scattering and diffraction (SAXS) techniques dedicated to research in structural biology and biophysics. The station provides state-of-the-art experimental facilities for structural studies on biological material such as nucleic acids, proteins, protein assemblies, virus particles, biological fibers as well as lipid membranes and membrane-protein/DNA complexes. In addition to supporting SAXS experiments on biological systems in equilibrium, BL4-2 also maintains state-of-the-art experimental facilities for time-resolved studies featuring a high photon flux multilayer monochromator, a fast readout photon counting detector (Pilatus3 X 1M) and a stopped-flow device optimized for biological samples providing access to reaction time scales in the milliseconds and above. The BL4-2 instrument features a pin-hole geometry x-ray scattering camera, which can be configured in different ways to accommodate a variety of data collection modes and experiments, including high throughput solution scattering, size-exclusion chromatography coupled solution scattering, general fixed-targed scattering and diffraction, low angle single crystal diffraction, fiber diffraction and gracing-incidence scattering and diffraction. A heavily customized version of the Blu-Ice/DCS software, originally developed for macromolecular crystallography experiments, is used to control the entire instrument providing an intuitive graphical user interface for all experiments.

The beamline BL4-2 is part of the SSRL Structural Molecular Biology Program and is supported by the DOE Office of Biological and Environmental Research and by the National Institutes of Health, National Institute of General Medical Sciences.