New System Makes X-Ray Free Electron Lasers More Accessible to Synchrotron Users

Artistic rendering shows the planned instrumentation for a macromolecular femtosecond crystallography
This artistic rendering shows the planned instrumentation for a macromolecular femtosecond crystallography (MFX) experimental station at the Linac Coherent Light Source. The simulated light flash shows where X-ray pulses strike a sample, producing a diffraction pattern (upper right, in purple) that can then be analyzed to reveal the 3-D structure of a biological molecule (bottom right). Credit: SLAC National Accelerator Laboratory

X-ray free electron lasers (XFELs) are powerful new tools for examining the detailed structures of biological macromolecules. XFELs can enable the characterization—at higher resolution than is possible at synchrotrons—of multiprotein complexes, membrane proteins and other important molecules that produce only micron-sized and/or very radiation-sensitive crystals, which make structural investigations especially difficult. Recently, a data collection system has been developed at the Stanford Synchrotron Radiation Lightsource (SSRL) for use at the world's first XFEL, the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory.

The highly automated new system uses an instrument familiar to crystallographers called a goniometer to precisely and rapidly position crystals into the X-ray beam. The goniometer can introduce samples that have been cryopreserved or are at room temperature. The system is complementary to those that deliver crystals in liquid jets or droplets into the beam. Whereas only a small fraction of the target crystals are exposed to the X-ray beam in a jet-delivery system, the goniometer-based system offers the major advantage that many fewer crystals need to be produced for the collection of a full data set. Additionally, if a crystal is large enough, the system allows for multiple exposures to be collected from different locations on the crystal.

Currently, the goniometer set-up must be transported from SSRL to the LCLS X-ray Pump/Probe (XPP) experimental station, installed for LCLS beamtime use and then disassembled. But a new, dedicated macromolecular femtosecond crystallography (MFX) experimental station under development at LCLS will make a similar, enhanced goniometer set-up permanently available to users. Other sample introduction modes will also be available at MFX, so researchers will be able to use the mode that best suits their experiments.

The goniometer-based set-up used at XPP was developed at the SSRL structural biology resource with support from NIGMS Biomedical Technology Research Resources grant P41GM103393 and in collaboration with LCLS.

The MFX construction project, launched in April 2014, is supported by the Department of Energy Office of Science's Office of Biological and Environmental Research and Office of Basic Energy Sciences, LCLS, Stanford University and NIGMS Biomedical Technology Research Resources grant P41GM103393.

Cohen A, Soltis S, Gonzalez A, et al. Goniometer-based femtosecond crystallography. Proc Natl Acad Sci USA. 2014 Dec 2;111(48), 17122-7. PMCID: PMC4260607.

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For additional information, contact Douglas M. Sheeley.