Single Molecule Holography Realized

I am very grateful that I could join, maybe one of the most exciting experimental efforts recently. It goes back to Denis Gabor, the inventor of holography, who really proposed an idea to improve electron microscopy (D. Gabor, A New Microscopic Principle, Nature 161, 777-778 (1948)).

Above is shown what Gabor suggested. A coherent point emitter shines electrons onto a suspended object and the a screen record the pattern that is formed by the unscattered wave interfering with the scattered part of the beam. The pattern is called the hologram. In it each point of the object creates an image that looks like a Fresnel lens. This kind of lens illuminated with light bundles it into one point again, by diffraction not refraction. And this is how the holographic image can be reconstructed, a hologram is illuminated with again coherent light and the object reappears.

Gabors idea was realized with light once the laser was invented (image below). For a holographic electron microscope there was no source and no sample holder at the time. These problems have now been solved and I had to chance to take part in the endeavor and deposit folded proteins onto the sample holder of freestanding graphene to be imaged in the holographic microscopy, with the images nowadays reconstructed in-silico.

Scheme of the holographic microscope. Below, a hologram and the reconstructed image of the protein BSA (scalebar 2nm).

Hans-Werner Finks group at the University of Zuerich built the holographic microscope for electrons. The emitter is a very sharp metal tip, the sample holder is ultrapure, freestanding graphene. And the molecule is placed on the surface with preparative mass spectrometry, hence with my ion beam deposition instrument.

Just now we published this in PNAS:

J.-N. Longchamp, S. Rauschenbach, S. Abb, C. Escher, T. Latychevskaia, K. Kern & H.-W. Fink: Imaging Proteins at the Single Molecule Level. Proc. Natl. Acad. Sci. U.S.A. doi:10.1073/pnas.1614519114 (2017)

and there was a nice accompanying article, nicely explaining the implications:

F. Forneris & A. Mattevi: Expanding the structural biology toolbox with single-molecule holography. Proc. Natl. Acad. Sci. U.S.A. (2017)

And also a few other outlets reported

NZZ article

MPG press release



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