SLAC National Accelerator Laboratory
The SSRL Structural Molecular Biology (SMB) resource, funded by DOE-BER and NIH-NIGMS, operates as an integrated facility with three cores of technological R&D and scientific focus:
- macromolecular crystallography (MC)
- small-angle x-ray scattering (SAXS)
- x-ray spectroscopy (XAS/XES) including x-ray microXAS imaging
There is significant synergy between the three cores in technological R&D and research to provide an integrated approach, enabling the use of multiple methods to address increasingly complex and challenging scientific problems. The resource operates 7 dedicated beam lines (4 MC, 1 SAXS, 2 XAS) and supports shared access to several other XAS/XES beam lines. The SMB resource is also a partner in R&D and user support of the Linac Coherent Light Source (LCLS; the x-ray free electron laser) facility’s Macromolecular Femtosecond Crystallography instrument. The SMB facility sustains and enhances the scientific user community through an extensive support, training and dissemination program.
The SMB resource is located at the Stanford Synchrotron Radiation Lightsource (SSRL), whose 3-GeV SPEAR3 storage ring provides low-emittance, high-brightness synchrotron light at 500 mA current, with top-off injection, providing annual run times of ~5,100 hrs with >97% delivery. SSRL is a DOE-funded national user facility at SLAC National Accelerator Laboratory, Menlo Park, California, and part of Stanford University.
Collectively, the study of the diffraction (MC), scattering (SAXS), absorption and emission (XAS/XES/imaging) of x-rays by biological materials provides a remarkably rich and broad window on structure and function across a range of biologically relevant length and time scales. As biological materials in general interact rather weakly with x-rays, and samples are often dilute, small or available in limited quantities, the unique properties of synchrotron radiation x-rays – extremely high intensity, tunability and high collimation – have come to play an increasingly important and transformative role in structural biology and imaging.
Macromolecular crystallography provides 3-dimensional structural knowledge of macromolecules, at atomic resolution. It requires that the biomolecules are present in a crystal, and studies range from individual proteins to large multi-protein complexes to membrane proteins. Increasingly these studies use micron-sized crystals, and are reaching into the time-domain.
Small-angle x-ray scattering provides structural and dynamics information from solutions or partially ordered arrays of biomolecules under physiologically relevant conditions, albeit at lower resolution (~7-10 Å or higher) compared to that obtainable from crystallography or cryo-electron microscopy. SAXS is a powerful tool for time-resolved studies and hence can be used to address questions like large conformational changes during enzyme reactions, protein-protein interactions, and folding intermediates.
X-ray spectroscopy provides electronic information and local chemical structure of metals at atomic resolution, and this on the key roles of metals in biological structure and function. Structural information (electronic and geometric) can be obtained from x-ray absorption edge and extended fine structure (EXAFS) experiments (collectively called XAS; local structure around the metal out to ~5 Å). Enhanced electronic information into the time-domain is addressed using x-ray emission (XES) spectroscopy. MicroXAS imaging provides spatially-resolved information on metal distribution and chemical speciation in biological materials, on length scales from nm to cm, from cells to tissues.
To address the most complex biological questions across a range of length and/or time scales that are not accessible using a single methodology, increasingly there is use of multiple methodologies with integration of the results from each.
Access to Facility
Access to the facility is via submission of beam time access proposals that undergo peer-review. Several mechanisms are available within this frame work. See Proposal Submittal and Scheduling Procedures for Research.
Points of Contacts