Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Mikroskopie und Tomographie Vortrag: Mi., 11:30–11:50 M-V2
Nano-Tomography and Spectromicroscopy with the new BESSY X-Ray Microscope
Gerd Schneider 1 , Peter Guttmann 1 , Stefan Rehbein 1 , Stefan Heim 1 , Diane
Eichert 1
1 BESSY m.b.H., Albert-Einstein-Str. 15
X-ray microscopy is a powerful imaging technique with many applications in materials,
environmental and life sciences. Among many scientific questions in life sciences, the
cell nucleus which is a vital and complex organelle is still a mystery. How the DNA
it contains and its associated proteins are arranged and packaged to fit within this
approx. 10 micron diameter organelle is unknown. The normal cellular contingent of
DNA is 105-fold longer than the nuclear diameter. Some DNA compaction (6-fold)
can be accounted for by its wrapping around nucleosomes. The nucleosomal fiber
is itself probably folded to yield a thicker fiber of 30 nm thickness, providing 7-fold
more compaction. How this “30 nm fiber” is folded to achieve the further necessary
compaction is unknown. Other questions of packaging concern how much “free” space
for diffusion is available in the nucleus.
The interaction of x-rays is element specific, therefore, x-ray nano-tomography can be
used to quantify the packing density of organic material. However, different proteins
or molecular structures cannot be distinguished directly in x-ray microscope images.
This problem is solved by the availability of specific fluorescent probes detectable by
fluorescence microscopy. Thus the two imaging modalities are complementary. Since
fluorescence and x-ray microscopy permit analysis of whole cells, it is possible to investigate
the same cell in both microscopes. These correlative studies are ideally suited
to x-ray microscopy because of its ability to image cells in 3D. We expect to develop a
widely applicable technique that, as applied to nuclear structure, will yield significant
new insights.
3D x-ray microscopy - pioneered at BESSY has found numerous applications worldwide.
To further improve 3D x-ray imaging towards sub-10 nm spatial resolution and
to increase the usable photon energy range by phase contrast methods, progress has to
be made in x-ray optics, instrumentation and theory. In the talk, the current status
and future aspects of x-ray microscopy at 3rd generation electron storage rings and
the upcoming Free Electron Lasers with their fs-pulses will be discussed.