Thesis-PDF - IAP/TU Wien

Crystalline Cell Parts
Crystalline cell parts had to be imaged after a series of preparation and purification
steps. Successful imaging included semicrystalline starch deposits (paramylum
grains) and cell parts. AFM imaging of such a cell part solution has never been
done before and in this sense the next images are unique. A view on a dried sample
by optical microscopy is seen in Fig. 6.15. Small lumps of material aggregated
and it often was difficult to locate intact cell parts within.
In comparison, in Fig. 6.16 a patch of dried crystalline cell part solution as
imaged by AFM is shown. This patch is of good quality because it does not only
contain the residue of dissolved biological material but also crystalline cell parts.
E.g. a paramylum grain can be spotted to the lower left of the image.
In Fig. 6.17 a feature often found in such a dried crystalline cell parts preparation
is seen. The size and shape of this feature correlate to those of a lipid body,
one of Euglena’s energy storage facilities.
The search for the photoreceptor of E. gracilis yielded the imaging of very
interesting regular structures such as the one in Fig. 6.18. Despite the layered
nature of the structure, further AFM investigation is needed for a more complete
assessment. An E. gracilis cell contains only one photoreceptor at a mass of only
about 1/20000th of that of the whole cell. Even in our purified solution a targeted
approach using AFM is difficult.
The last figure, Fig. 6.19, gives a 3D-view of a paramylum grain based on AFM
height information. It confirms the overall concentric pattern found in such a grain
stemming from the crystalline assembly of microfibrils only 4 nm in diameter. On
page 60, Fig. 4.18 shows a SEM image of a freeze-fractured paramylum grain. The
details of the microfibril assembly are not yet fully understood. ([108], [113])
Figure 6.15: The cantilever scanning over a dried solution of crystalline
cell parts. Image taken by optical light microscopy (transmitted light).
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