The biophysically oriented research group studies transport processes of electrons and ions in membrane-bound protein complexes, employing modern methods of paramagnetic electron spin resonance (EPR), electron-electron double resonance (ELDOR) and electron-nuclear double resonance (ENDOR). The spectroscopic data are analyzed by state-of-the-art quantum-chemical methods to determine the electronic and geometrical structures (distances and orientations) of the molecules involved in the biological process, including their conformational changes during the reaction.

These activities are fully integrated in the Special Research Project SFB 498 and the Priority Program SPP 1051 of the Deutsche Forschungsgemeinschaft (DFG) with numerous external collaborations with scientists in USA, Russia, Israel, Japan, The Netherlands, Italy, Poland and Germany.

The current research topics of interest are:

High-field/high-frequency EPR: High-field/high-frequency EPR: Development of new stationary and pulsed EPR, ENDOR, ESEEM and ELDOR methods at high magnetic fields and microwave frequencies, e.g., at 6 T/95 GHz and at 14 T/360 GHz.

Photosynthesis: Elucidation of the relationship between structure, dynamics and function of directed electron-transfer processes in reaction centers of photosynthesis and control of the electron pathway by site-specific mutagenesis of photosynthetic bacteria and plants. Moreover, the molecular switching mechanism of the light-driven vectorial proton-tranfer process in site-directed mutants of spin-labeled bacteriorhodopsin is studied.

Repair of UV-induced damages in DNA: Here the focus of interest is on the identification of intermediate irradiation products and the understanding of the mechanism of the light-driven repair of UV-induced damages of the DNA by the enzyme DNA-photolyase.

Formation of membrane-channels by cell toxins: Certain bacterial cell toxins, such as Colicins, can cause the formation of ion channels in the cell membrane by massive refolding of their protein structure. This leads to subsequent "bleeding to death" of the cell. We want to understand these toxin-induced protein refolding processes on a molecular level by employing site-directed spin-labeling and high-field EPR techniques.

Transporter proteins: Transmembrane sodium/substrate transporters, such as the Na(+)/Proline transporter PutP of E.coli, are essential for cell nutrition. They use the energy stored in the electrochemical sodium gradient to drive the substrate accumulation in the cell. We want to determine distances and orientations of selectively spin-labeled transmembrane protein domains involved and the dynamics of helix and loop regions during substrate transport.

Data analysis by Density Functional Theory (DFT) calculations: Characteristic shifts of g-, hyperfine- and quadrupole-tensor components are interpreted in terms of changes in the geometric and electronic molecular structure, explicitly including hydrogen-bond effects. Of particular interest are site-directed NO spin labels in their protein environment as well as cofactor ion radicals in mutant bacterial reaction centers. To extract such information, the experimental data are analyzed by state-of-the-art quantum chemical calculations. Specifically, modern DFT programs are used to interpret the experimental results.