Physical Society Colloquium

Femtosecond nanodiffraction using a hard X-ray laser

John Spence

Physics Department
Arizona State University & LBNL

A summary of recent results will be presented from the Linac Coherent Light Source (LCLS) at Stanford. This produces 2 - 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 Photosystem 1 (PS I) protein nanocrystals. 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. The sum of these spot patterns forms an indexable virtual "powder pattern". In this way radiation damage of delicate membrane proteins is avoided. Each pulse produces one pattern from one 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. New solutions to the phase problem are suggested by this work. I will also discuss preliminary pump-probe experiments on PS I-ferredoxin with this apparatus, and results from PS II. Experiments using correlations in fast WAXS patterns are also reviewed. For reviews and more information on this approach to nanocrystallography of hydrated samples, see [1,2,3].

[1] Chapman, H. Nature Materials. 8, 299 (2009)
[2] Kirian, Spence et al Optics Express 18, 5713 (2010)
[3] Kirian, et al. Acta Cryst A (2010). Submitted.