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Serial femtosecond crystallography

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Serial femtosecond crystallography (SFX) is a form of X-ray crystallography developed for use at X-ray free-electron lasers (XFELs).[1][2][3] Single pulses at free-electron lasers are bright enough to generate resolvable Bragg diffraction from sub-micron crystals. However, these pulses also destroy the crystals, meaning that a full data set involves collecting diffraction from many crystals. This method of data collection is referred to as serial, referencing a row of crystals streaming across the X-ray beam, one at a time.

Serial Femtosecond Crystallography (SFX) schematic

History

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While the idea of serial crystallography had been proposed earlier,[4] it was first demonstrated with XFELs by Chapman et al.[5] at the Linac Coherent Light Source (LCLS) in 2011. This method has since been extended to solve unknown structures, perform time-resolved experiments, and later even brought back to synchrotron X-ray sources.

Methods

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In comparison to conventional crystallography, where a single (relatively large) crystal is rotated in order to collect a 3D data set, some additional methods have to be developed to measure in the serial mode. First, a method is required to efficiently stream crystals across the beam focus. The other major difference is in the data analysis pipeline. Here, each crystal is in a random, unknown orientation which must be computationally determined before the diffraction patterns from all the crystals can be merged into a set of 3D hkℓ intensities.

Sample Delivery

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The first sample delivery system used for this technique was the Gas Dynamic Virtual Nozzle (GDVN) which generates a liquid jet in vacuum (accelerated by a concentric helium gas stream) containing crystals. Since then, many other methods have been successfully demonstrated at both XFELs and synchrotron sources. A summary of these methods along with their key relative features is given below:

  • Gas Dynamic Virtual Nozzle (GDVN)[6] - low background scattering, but high sample consumption. Only method available for high repetition rate sources.[7]
  • Lipidic Cubic Phase (LCP) injector[8] - Low sample consumption, with relatively high background. Specially suited for membrane proteins
  • Other viscous delivery media[9][10] - Similar to LCP, low sample consumption with high background
  • Fixed target scanning systems (wide variety of systems have been used with different features, with standard crystal loops,[11] or silicon chips[12]) - Low sample consumption, background depends on system, mechanically complex
  • Tape drive (crystals auto-pipetted onto a Kapton tape and brought to X-ray focus) - Similar to fixed target systems, except with fewer moving parts

Data Analysis

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In order to recover a 3D structure from the individual diffraction patterns, they must be oriented, scaled and merged to generate a list of hkℓ intensities. These intensities can then be passed to standard crystallographic phasing and refinement programs. The first experiments only oriented the patterns[13] and obtained accurate intensity values by averaging over a large number of crystals (> 100,000). Later versions correct for variations in individual pattern properties such as overall intensity variations and B-factor variations as well as refining the orientations to fix the "partialities" of the individual Bragg reflections.[14]

References

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  1. ^ Liu, W.; et al. (2013). "Serial Femtosecond Crystallography of G Protein–Coupled Receptors - PubAg". Science. 342 (6165). US: United States National Agricultural Library: 1521–1524. doi:10.1126/science.1244142. PMC 3902108. PMID 24357322. Retrieved 2019-02-26.
  2. ^ Mizohata E, Nakane T, Fukuda Y, Nango E, Iwata S (April 2018). "Serial femtosecond crystallography at the SACLA: breakthrough to dynamic structural biology". Biophysical Reviews. 10 (2): 209–218. doi:10.1007/s12551-017-0344-9. PMC 5899704. PMID 29196935.
  3. ^ Martin-Garcia JM, Conrad CE, Coe J, Roy-Chowdhury S, Fromme P (July 2016). "Serial femtosecond crystallography: A revolution in structural biology". Archives of Biochemistry and Biophysics. 602: 32–47. doi:10.1016/j.abb.2016.03.036. PMC 4909539. PMID 27143509.
  4. ^ Neutze R, et al. (August 2000). "Potential for biomolecular imaging with femtosecond X-ray pulses". Nature. 406 (6797): 752–757. doi:10.1038/35021099. PMID 10963603. S2CID 4300920.
  5. ^ Chapman HN, Fromme P, Barty A, White TA, Kirian RA, Aquila A, et al. (February 2011). "Femtosecond X-ray protein nanocrystallography". Nature. 470 (7332): 73–7. Bibcode:2011Natur.470...73C. doi:10.1038/nature09750. PMC 3429598. PMID 21293373.
  6. ^ DePonte DP, Weierstall U, Schmidt K, Warner J, Starodub D, Spence JC, Doak RB (September 2008). "Gas dynamic virtual nozzle for generation of microscopic droplet streams". Journal of Physics D: Applied Physics. 41 (19): 195505. arXiv:0803.4181. Bibcode:2008JPhD...41s5505D. doi:10.1088/0022-3727/41/19/195505. S2CID 119259244.
  7. ^ Wiedorn MO, Awel S, Morgan AJ, Ayyer K, Gevorkov Y, Fleckenstein H, et al. (September 2018). "Rapid sample delivery for megahertz serial crystallography at X-ray FELs". IUCrJ. 5 (Pt 5): 574–584. doi:10.1107/S2052252518008369. PMC 6126653. PMID 30224961.
  8. ^ Weierstall U, James D, Wang C, White TA, Wang D, Liu W, et al. (2014). "Lipidic cubic phase injector facilitates membrane protein serial femtosecond crystallography". Nature Communications. 5: 3309. Bibcode:2014NatCo...5.3309W. doi:10.1038/ncomms4309. PMC 4061911. PMID 24525480.
  9. ^ Sugahara M, Mizohata E, Nango E, Suzuki M, Tanaka T, Masuda T, et al. (January 2015). "Grease matrix as a versatile carrier of proteins for serial crystallography". Nature Methods. 12 (1): 61–3. doi:10.1038/nmeth.3172. hdl:2433/203008. PMID 25384243. S2CID 25950836.
  10. ^ Conrad CE, Basu S, James D, Wang D, Schaffer A, Roy-Chowdhury S, et al. (July 2015). "A novel inert crystal delivery medium for serial femtosecond crystallography". IUCrJ. 2 (Pt 4): 421–30. doi:10.1107/S2052252515009811. PMC 4491314. PMID 26177184.
  11. ^ Gati C, Bourenkov G, Klinge M, Rehders D, Stellato F, Oberthür D, et al. (March 2014). "Serial crystallography on in vivo grown microcrystals using synchrotron radiation". IUCrJ. 1 (Pt 2): 87–94. doi:10.1107/S2052252513033939. PMC 4062088. PMID 25075324.
  12. ^ Roedig P, Ginn HM, Pakendorf T, Sutton G, Harlos K, Walter TS, et al. (August 2017). "High-speed fixed-target serial virus crystallography". Nature Methods. 14 (8): 805–810. doi:10.1038/nmeth.4335. PMC 5588887. PMID 28628129.
  13. ^ White TA, Kirian RA, Martin AV, Aquila A, Nass K, Barty A, Chapman HN (April 2012). "CrystFEL: a software suite for snapshot serial crystallography" (PDF). Journal of Applied Crystallography. 45 (2): 335–41. doi:10.1107/S0021889812002312.
  14. ^ White TA, Mariani V, Brehm W, Yefanov O, Barty A, Beyerlein KR, Chervinskii F, Galli L, Gati C, Nakane T, Tolstikova A, Yamashita K, Yoon CH, Diederichs K, Chapman HN (April 2016). "Recent developments in CrystFEL". Journal of Applied Crystallography. 49 (Pt 2): 680–689. doi:10.1107/S1600576716004751. PMC 4815879. PMID 27047311.
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