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A fixed-target platform for serial femtosecond crystallography in a hydrated environment

By 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

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Category

BioXFEL Publications

Published on

Type

journal-article

Author

M. L. Shelby and D. Gilbile and T. D. Grant and C. Seuring and B. W. Segelke and W. He and A. C. Evans and T. Pakendorf and P. Fischer and M. S. Hunter and A. Batyuk and M. Barthelmess and A. Meents and M. A. Coleman and T. L. Kuhl and M. Frank

Citation

Shelby, M.L. et al., 2020. A fixed-target platform for serial femtosecond crystallography in a hydrated environment. IUCrJ, 7(1), pp.30–41. Available at: http://dx.doi.org/10.1107/s2052252519014003.

Abstract

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.

DOI

http://dx.doi.org/10.1107/s2052252519014003

Funding

NSF-STC Biology with X-ray Lasers (NSF-1231306)