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SUMMARY:Femtosecond Membrane-Protein Nanodiffraction using a Hard X-Ray La
 ser - John Spence\, Arizona State University
DTSTART:20101123T161500Z
DTEND:20101123T180000Z
UID:TALK25849@talks.cam.ac.uk
CONTACT:Scientific Meetings Co-ordinator
DESCRIPTION:A summary of recent results will be presented from the Linac C
 oherent 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 b
 eam\, which we have use to obtain diffraction patterns from millions of su
 bmicron Photosystem I (PS I)\, PS II and PSI-ferredoxin\, protein nanocrys
 tals 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 diffr
 act-and-destroy mechanism in which a useful diffraction pattern is formed 
 before the nanocrystal is vaporised.  In this way radiation damage of deli
 cate membrane proteins is avoided. Each pulse produces one pattern from on
 e randomly oriented nanocrystal\, which is read out\, and the process repe
 ated at 60 Hz. We have assesed the quality of the data by comparison with 
 synchrotron data. Data analysis for these partial reflections\, and new so
 lutions 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  discus
 s preliminary time-resolved pump-probe experiments on PS I-ferredoxin undo
 cking 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 o
 riented identical particles\, ab initio\, without modelling. For more info
 rmation\, see [1\,2\,3\,4].\n\nA workshop on X-ray lasers in Biology will 
 be help in Berkeley from Jan 18\, 2011.  See  https://sites.google.com/a/l
 bl.gov/biology-with-fels/\n\n \n\n*and the SLAC/CFEL Hamburg/Heidelburg MP
 I/ASU collaboration. See  Chapman et al Nature\, Submitted. (2010) for a f
 ull author list.\n\n1. Chapman  Nature Materials. 8\, 299 (2009)\n\n2. Kir
 ian\, Spence  et al  Optics Express  18\, 5713 (2010).\n\n3. Kirian\, et a
 l. Acta Cryst A (2010). Submitted.\n\n4. Saldin et al. New J. Phys.  12\, 
 035014 (2010).
LOCATION:Max Perutz Lecture Theatre\, Medical Research Council (MRC) (MRC 
 Laboratory of Molecular Biol
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