biophysics is among the most expanding fields in physics. In my opinion biophysics, the application of techniques developed by physicists on biological problems will continue to be a fruitful field in physics. In all biological processes molecules are involved. My motivation was always to understand the dynamics and interplay of these molecules which enables life in general. In my life as a biophysicist I had the chance to work on many different classes of biologically relevant molecules including deoxyribonucleic acids (DNA), peptides and other organic molecules. This required me to learn a lot of different techniques to study these molecules: Atomic force spectrosopy, ultrafast IR spectroscopy, just to name a few. Currently I am working as a Postdoc in the group of Dr. Markus Braun on ultrafast X-ray scattering of molecular crystals. This web-page is intended to give an overview over my scientific life so far.

X-ray scattering has been widely used to solve the structures of protiens in molecular crystals with Ångström spatial resolution. But knowing its structure does not mean that one can understand the function of a protein. This is only possible if one can follow the structural dynamics during its functional cycle in real time. Since these structural changes may take place on the time scale of molecular vibrations, time resolutions of 100 fs are required. My Postdoc project is a challenging one which combines the structural sensitivity of X-ray scattering with the supreme time resolution of pump probe spectroscopy (~100 fs). In the picture to the left a molecular crystal of diisopropylaminobenzonitrile is shown, which is a protype for molecular crystals. It shows the rotation of a functional group upon excitation with ultraviolet light (="function"). The problems involved in the attempt to measure this rotation by ultrafast X-ray scattering has been discussed in our recent publication (M. Braun et al., PRL 98 (2007) 248301).

Deseases like Alzheimer and Creutfeldt Jacob are believed to have a common origin in fibrillar peptide aggregates. In these cases the folding of the peptides has not led to the desired funtional structure but to some different form of peptide which causes the severe deseases mentioned above. This protein folding problem is among the most challenging ones in biophysics. To tackle this problem we investigate model peptides and their folding behaviour in order to understand more about secondary structure formation and early folding events in larger proteins. These model peptides (for an example see picture on the right) feature a molecular switch (in most cases azobenzene) which triggers the folding process upon its excitation with light. In doing so we can synchronize the folding dynamics of many model peptides with a precision of better than 10 ps. This enable us to follow the folding processes step by step in real time. As a structure sensitive detection tool I used time resolved broad band IR-spectroscopy in the range of the amide-I vibration of the peptide backbone. With this technique we recently succeeded in measuring the folding and unfolding speed of a light-switchable &beta-Hairpin peptide (Schrader et al., PNAS 104 (2007) 15734).

An experimental set-up which combines single molecule fluorescence spectroscopy with atomic force spectroscopy enables the study of the fluorescence propreties of a dye molecule with an applied force to it. As a model system for such an experimental set-up I investigated the mechanical property of a DNA-sample with the intercalating dye ethidiumbormide added. In the picture on the left you see a schematic on how the dye molecule (green) is placed in the middle of two DNA base pairs (blue). The mechanical influence of the intercalating dye molecule on the DNA-sample proved to be of scientific interest in itself. Later on the suitability of this model system as a molecular chain of lights was shown in a combined force and fluorescence spectoscopic experiment.