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Biological Laboratory X-Ray Microscopy

Time: Fri 2020-08-21 13.00

Location: FD5 eller via zoom, Du som saknar dator/datorvana kan kontakta Thomas Frisk, för information, Roslagstullsbacken 21, Stockholm (English)

Subject area: Biological and Biomedical Physics Optics and Photonics

Doctoral student: Mikael Kördel , Biomedicinsk fysik och röntgenfysik

Opponent: Dr Rajmund Mokso, Lunds universitet, Lund

Supervisor: Hans Hertz, Fysik, Fysik, Biomedicinsk fysik och röntgenfysik, Albanova VinnExcellence Center for Protein Technology, ProNova; Ulrich Vogt, Biomedicinsk fysik och röntgenfysik; Jonas A. Sellberg, Biomedicinsk fysik och röntgenfysik

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Soft x-ray microscopy in the water window (𝜆 ≈ 2.3 − 4.3 nm) is a powerful technique for high-resolution biological imaging. The strong natural contrast between carbon-based structures and water allows visualization of hydrated and unstained samples, while providing enough transmission through up to ∼ 10 μm of organic matter. Furthermore, the full potential of this technique can be exploited by performing computed tomography, thus obtaining a complete 3D image of the object.

Routine short-exposure water-window microscopy of whole cells and tissue is currently performed at synchrotron-radiation facilities around the world, but with a limited accessibility to the wider research community. For this reason, laboratory-based systems have been developed, which are now reaching maturity. The benefits compared to the synchrotron-based instruments include easier integration with complementary methods in the home laboratory, in addition to the increased access that allows for the often time-consuming optimization of experimental parameters as well as longitudinal studies.

This Thesis presents recent developments of the Stockholm laboratory x-ray microscope as well as several biological applications. Work has been done on improving the mechanical and thermal stability of the microscope, resulting in a resolution of 25 nm (half period) in images of test targets. The biological applications were enabled by a significantly increased x-ray flux through the system as well as an improved operational stability. This work demonstrates 10-second exposure imaging of whole cryofixed cells, imaging of viral infections in cells, and 20 minutes total exposure cryotomography.