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Ph.D. Thesis
Cellular X-‐ray Imaging with ultra-‐short Pulses
Novel X-‐ray sources such as Free Electron Lasers (FEL) and laser driven compact X-‐ray sources enable entirely new imaging capabilities. High resolution density maps of biological cells can be measured by ultra-‐short pulses, circumventing the need of fixation or slicing of the sample as well as effects of radiation damage[1]. To exploit these capabilities, the current iterative phase reconstruction algorithms and imaging modes will be surveyed in view of this application. The use of single pulses and the size of the eukaryotic cells as opposed to small bacteria and viruses, which have been imaged so far at FEL sources, necessitates adaptation of the experimental design and algorithms. Secondly, appropriate aqueous sample environment for sample delivery have to be devised. The current project will test an existing microfluidic water jet for high throughput delivery of cells, using also nano-‐focused synchrotron radiation[2], in view of the parameters compatible with live cells delivery and high hit rates. Finally, proof-‐of-‐concepts experiments shall be carried out. The research is funded by Nanoscale Photonic Imaging SFB 755 as well as the Virtual Institute 'In-‐Situ Nano-‐Imaging of Biological and Chemical Processes provisional schedule line', in close collaboration with the group of Prof. Dr. Sarah Köster, as well as with collaborating groups at HASAYLAB/DESY.
[1] Hajdu, J. et al. Single mimivirus particles intercepted and imaged with an X-‐ray laser. Nature 470, 78–82 (2011)
[2] Priebe, M. et al. Orientation of biomolecular assemblies in a microfluidic jet. New J. Phys. 12, 043056 (2010)
Figure: Functional principle of the liquid jet as sample delivery system. Observed diffraction pattern of a particle within the water jet using soft X-ray FEL (FLASH). Radial intensity profile exhibiting a strong diffraction streak orthogonal to the jet, with an oscillatory intensity profile. This modulation can be analyzed in terms of the water interface (jet geometry, capillary waves, near-molecular density profile, break-up instabilities).
Contact
Assistance: Dr. Dong-Du Mai Tel: +49 (0)551 - 39 - 14 41 4 · Email: [email protected]
Head of Institute: Prof. Dr. Tim Salditt Tel: +49 (0)551 - 39 - 94 27 · Email: [email protected]
