Physik auf der Nanometer Skala und/oder Biophysik

Allgemeines:

Bachelor-Arbeiten: Die Bachelorarbeit in Physik besteht aus einer aktiven Mitarbeit in einer der Forschungsgruppen. Das Resultat der Arbeit wird in einem schriftlichen Bericht festgehalten und in einem Vortrag dargestellt. Die Bachelorarbeit wird benotet.

Master-Arbeiten: Nach Auswahl des Themas der Masterarbeit nach Absprache mit dem Betreuer, geht es zunächst darum, ein sorgfältiges Forschungsproposal zu verfassen, das im Rahmen eines Vortrags im Gruppenseminar vorgestellt wird. Die Masterarbeit ist eine selbständige Forschungsarbeit, die etwa 9 Monate (Richtzeit) dauert.

Weitere Informationen finden Sie hier.

Die unten aufgelisteten Themen sind sowohl für Bachelor- als auch Master-Arbeiten geeignet, natürlich nach entsprechender Anpassung der zum jeweiligen Thema zu erreichenden Ziele.

Subjects - updated fall 2009

Study of carbon nanotubes functionalized with bio-molecules

Low-energy electron holography and low-energy electron oversampling imaging are the only two methods, known to exist, which enable us to observe single bio-molecules at high resolution without damaging them. The experiments request that the bio-molecules should be free-standing, for instance over 100nm-1000nm holes or slits milled in a thin carbon film. Since the bio-molecules of interest are smaller than theses holes, they have to be carried. Functionalized carbon nanotubes appear as one of the best possible carrier for bio-molecules.
A Bachelor or Master thesis is related to these efforts by carrying out sample preparations of carbon nanotubes deposited onto thin carbon films and imaging them in a transmission electron microscope. Furthermore, TEM imaging of proteins, for instance Ferritin, attached to functionalized nanotubes should be also be carried out.

For more information contact: Jean-Nicolas Longchamp

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Diffusion of C 60 clusters on tungsten surfaces

This project is related to the set-up and methods of the practicum experiment in connection with the lecture “Physik auf der Nanometer-Skala”. The diffusion of C-60 clusters (so-called buckyballs) on tungsten surfaces shall be measured from experimentally derived auto-correlation functions of the field electron current from a C 60 covered tungsten tip surface. The decay time of the current autocorrelation function at different temperatures shall reveal the diffusion coefficient for C 60 on tungsten.

This project is related to the development of coherent electron sources for which information about the thermal stability of individual C-60 clusters onto field emitter tips is of importance

The development of coherent electron sources is related to a collaboration within the EU Project “SIBMAR” aiming at structural information on single molecules by electron holography

The earliest starting date for this study July 09

For more information contact: Conrad Escher

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Numerical hologram reconstruction

Holography with low energy electrons, exhibiting wave length between 0.01 to 0.1 nm is believed, at least by us, to have the potential of structural biology at the single molecule level. An electron hologram forms when an object (a single biological molecule) is placed in the path of the coherent electron wave.

The holographic record is recorded by a CCD chip and reconstructed numerically by back propagation of the field distribution. The result is a three-dimensional structure monitored on a computer screen. The tiny wavelength of the electrons provides sub-nm resolution in the reconstructed object. Eventually, three-dimensional spatial structural information with high resolution would provide the first tool for structural biology on a single molecule level. While the core of the reconstruction routine has been created, there are related problems to be solved which can be considered for a Bachelor or Master thesis.

A more experimentally oriented subject concerns the reconstruction of electron holograms using visible light from a green laser. Employing cross correlation to align subsequently acquired noisy holograms to produce a high single to noise holographic record is another subject which would mainly be concerned with numerical respectively programming work.

The above projects are related to a collaboration within the EU Project “SIBMAR” aiming at structural information on single molecules by electron holography.

For more information contact: Tatiana Latychevskaia

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Thermal desorption spectroscopy of water molecules bound to biomolecules

It is believed that water, bound to biological molecules, has a significant effect on the free energy landscape of a protein and with this on its function. This project aims at measuring the binding energy of water molecules towards different biological molecules, like a protein or a DNS strand. The molecules shall first be embedded into a thin amorphous ice layer and kept at liquid nitrogen temperature. After the transfer into a vacuum chamber, the samples shall be heated up while the water vapour pressure is measured with a quadrupole mass spectrometer. The thermal desorption spectra (water vapour pressure with increasing temperature) provide information on the binding of water to the specific molecule of interest.

The above project is related to a collaboration within the EU Project “SIBMAR” aiming at structural information on single molecules by electron holography

For more information contact: Conrad Escher

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Design of a miniaturized electron lens

Electron lenses exhibit intrinsic aberrations which is one of the reasons why the achievable resolution in modern microscopes is still orders of magnitude larger than the De Broglie wave length of the electrons. We have started an effort to circumvent the inherent lens aberrations by scaling down the lens to micrometer dimensions and by employing an atomic sized electron source.

A Bachelor or Master thesis is related to these efforts by carrying out ray tracing calculations with an existing software package. By regarding the boundary conditions of what is achievable in view of our abilities to machine materials on the nanometer-scale in our laboratory, the goal is to find an appropriate and realistic lens design, respectively a completely down-scaled electron column (in the case of a Master thesis).

The above project is related to collaboration with the University of California at Los Angeles and supported by the Swiss National Science Foundation. The overall goal is to achieve structural information about a single molecule by coherent electron diffraction.

For more information contact: Elvira Steinwand and/or Jean-Nicolas Longchamp

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January 2009: Workshop on “Current Trends of Structural Biology on the Single Molecule Level” associated with the EU project SIBMAR.

Subject fields shall be: Cryo-Electron Microscopy, X-ray methods including envisioned applications of X-ray Free Electron Lasers, Electron Holography, Coherent Diffraction and Oversampling.