Coherent diffraction imaging of single particles and biomolecules

The centre of investigations will be at

• the VUV-FEL in Hamburg
• the LCLS when it comes to life in about 2008,
• and the sub-10-fs source in Munich (10⁷ – 10⁸ photons/s)

till TT-XFEL becomes operational in 2009. Soft X-ray lasers (such as the VUV-FEL of DESY) will provide the first opportunities to test predictions on amage formation on ultrashort time scales and at extreme photon intensities. Besides testing methods of sample manipulation and injection in cooperation with C.3.1 we will validate methods of classifying and averaging diffraction patterns, and will reconstruct 3D structures from diffraction data sets. Although the shortest wavelength of soft-X-ray lasers precludes atomic resolution imaging, this source will be essential to validate the diffraction-based imaging technique. The experiments will give direct and compelling evidence of the viability of the models and determine the capabilities of the imaging technique of single-particle X-ray diffraction. The dynamics of the sample explosion will be followed over the very short duration of the pulse by measuring small-angle scattering on a stream of exploding particles, using the soft-X-ray FEL. Protein conformation in the gas phase will be investigated by using techniques from electro-spray ionisation mass spectrometry and flow cytometry. We will measure the radius of gyration from clouds of mass-selected particles by small-angle scattering. A method of parallel coherent imaging to relax FEL pulse requirements will be tested at synchrotrons. This will be based on coherent diffractive imaging from a beam of hydrated molecules injected into a vacuum chamber. Alignment of the molecules will be attempted with optical lasers. Such experiments will be carried out on a stream of particles exposed to coherent synchrotron radiation, and later also at the LCLS. All experiments will be dramatically improved when the Stanford radiation source becomes available (Dr. Hajdu is taking up a position as head of the Stanford single-molecule-imaging programme). Simulations have guided the work so far, and will play a significant role in the future of this project as the first experimental results start pouring in.