Gemeinsames Kolloquium

1
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 (13C and 15N) 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 29Si and to study these integer,
shock frozen cells by solid-state 29Si 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 29Si 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