Molekulare Biophysik Gemeinsames Kolloquium Referent Prof Dr Eike

Molekulare Biophysik Gemeinsames Kolloquium Referent: Prof. Dr. Eike Brunner TU Dresden Thema: Biomineralization in diatoms. An NMR spectroscopic study Diatom cell walls are outstanding examples of nanoscale structured materials in nature. The degree of complexity in these hierarchically organized biominerals has never been matched in artificial materials. Diatom cell walls consist of an amorphous composite material containing silica as well as certain biomolecules. These biomolecules could be made accessible to NMR spectroscopy by the development of efficient isotope-labelling strategies (13 C and 15 N) for diatom cells. This allowed us to perform extended solid-state NMR spectroscopic studies of the biomolecules incorporated into the cell walls. Furthermore, extraction, separation, and purification of the isotope-labelled biomolecules from the siliceous cell walls enabled us to perform detailed solution NMR spectroscopic studies. In combination with dynamic light scattering, and mass spectrometry, various post-translational modifications of the molecules found in the cell walls were identified. These studies also revealed the ability of multivalent anions (in particular phosphate) to initiate self-assembly processes of the biomolecules; an ability which is of crucial importance for the templating mechanisms taking place during cell wall patterning. Recently, we have developed a methodology to pulse label synchronized diatom cultures with 29 Si and to study these integer, shock frozen cells by solid-state 29 Si MAS NMR spectroscopic experiments. This method can be used to investigate the silicon uptake and metabolism of diatoms quantitatively. A great advantage of NMR compared to other techniques is that the 29 Si chemical shift sensitively reflects the chemical environment and polymerization state of the silicon. It is, furthermore, advantageous that the investigations are performed on integer, untreated cells. The cells can be studied at defined developmental stages as determined by fluorescence microscopy. Our NMR-based methodology allows for example to analyze the tentative silica precursor compounds formed during the cell division cycle. In summary, solid-state NMR spectroscopy in combination with liquid-state NMR, fluorescence microscopy, dynamic light scattering and other techniques turned out to be extremely useful for the study of biomineralization in diatoms as well as for the characterization of biomimetically synthesized silica materials. Ort: HS 18, Zoologie Johann-Joachim-Becher-Weg 9 Zeit: Montag, 16. 06. 2008, 17. 15 Uhr Info: http: //iabserv. biologie. uni-mainz. de/index. php Biologie