A fixed-target platform for serial femtosecond crystallography in a hydrated environment
M. L. Shelby,
D. Gilbile,
T. D. Grant,
C. Seuring,
B. W. Segelke,
W. He,
A. C. Evans,
T. Pakendorf,
P. Fischer,
M. S. Hunter,
A. Batyuk,
M. Barthelmess,
A. Meents,
M. A. Coleman,
T. L. Kuhl,
M. Frank
Affiliations
M. L. Shelby
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
D. Gilbile
University of California at Davis, California, USA
T. D. Grant
Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, Hauptman-Woodward Institute, SUNY University at Buffalo, Buffalo, New York, USA
C. Seuring
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Hamburg, Germany
B. W. Segelke
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
W. He
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
A. C. Evans
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
T. Pakendorf
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Hamburg, Germany
P. Fischer
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Hamburg, Germany
M. S. Hunter
Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California, USA
A. Batyuk
Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California, USA
M. Barthelmess
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Hamburg, Germany
A. Meents
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Hamburg, Germany
M. A. Coleman
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
T. L. Kuhl
University of California at Davis, California, USA
M. Frank
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
For serial femtosecond crystallography at X-ray free-electron lasers, which entails collection of single-pulse diffraction patterns from a constantly refreshed supply of microcrystalline sample, delivery of the sample into the X-ray beam path while maintaining low background remains a technical challenge for some experiments, especially where this methodology is applied to relatively low-ordered samples or those difficult to purify and crystallize in large quantities. This work demonstrates a scheme to encapsulate biological samples using polymer thin films and graphene to maintain sample hydration in vacuum conditions. The encapsulated sample is delivered into the X-ray beam on fixed targets for rapid scanning using the Roadrunner fixed-target system towards a long-term goal of low-background measurements on weakly diffracting samples. As a proof of principle, we used microcrystals of the 24 kDa rapid encystment protein (REP24) to provide a benchmark for polymer/graphene sandwich performance. The REP24 microcrystal unit cell obtained from our sandwiched in-vacuum sample was consistent with previously established unit-cell parameters and with those measured by us without encapsulation in humidified helium, indicating that the platform is robust against evaporative losses. While significant scattering from water was observed because of the sample-deposition method, the polymer/graphene sandwich itself was shown to contribute minimally to background scattering.
