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Femtosecond Membrane-Protein Nanodiffraction using a Hard X-Ray Laser

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A summary of recent results will be presented from the Linac Coherent Light Source (LCLS) at Stanford, the first hard X-ray laser. This produces 1- 8 kV pulses of X-rays of 10 -300 fs duration in a 3 micron beam, which we have use to obtain diffraction patterns from millions of submicron Photosystem I (PS I), PS II and PSI -ferredoxin, protein nanocrystals prepared in the Fromme lab at ASU . These are supplied fully hydrated in a liquid jet running in vacuum across the LCLS beam. We study the diffract-and-destroy mechanism in which a useful diffraction pattern is formed before the nanocrystal is vaporised. In this way radiation damage of delicate membrane proteins is avoided. Each pulse produces one pattern from one randomly oriented nanocrystal, which is read out, and the process repeated at 60 Hz. We have assesed the quality of the data by comparison with synchrotron data. Data analysis for these partial reflections, and new solutions to the phase problem based on them (which may help us emerge from the swamp of model-bias in the PDB ) will be discussed. I will also discuss preliminary time-resolved pump-probe experiments on PS I -ferredoxin undocking with this apparatus. Experiments using correlations and fluctuations in “snap-shot” SAXS patterns are also reviewed, in which an image of one particle has been reconstructed using the scattering from many randomly oriented identical particles, ab initio, without modelling. For more information, see [1,2,3,4].

A workshop on X-ray lasers in Biology will be help in Berkeley from Jan 18, 2011. See

*and the SLAC /CFEL Hamburg/Heidelburg MPI /ASU collaboration. See Chapman et al Nature, Submitted. (2010) for a full author list.

1. Chapman Nature Materials. 8, 299 (2009)

2. Kirian, Spence et al Optics Express 18, 5713 (2010).

3. Kirian, et al. Acta Cryst A (2010). Submitted.

4. Saldin et al. New J. Phys. 12, 035014 (2010).

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