The term "biomineralisation" denotes the formation of inorganic
material under the control of an organism. The main function of these
biominerals is the stabilisation and protection of the soft organic tissue.
Examples are the calcium phosphates of bones and teeth of vertebrate animals
as well as the shells of mussels or algae consisting of calcium carbonate
or silica. These biominerals exhibit remarkable material properties. Today,
the industrial production of these materials is hardly possible. Therefore,
it is important to analyse and understand the basic processes and principles
of biomineralisation in nature.
Diatoms are unicellular, photosynthetic eukaryotes, which can be found
in sea as well as in freshwater. They play a crucial role in the fixation
of CO2 and circulation of SiO2 in the oceans. However,
their most striking feature is their art-specific silicified cell wall
which exhibits beautiful, regularly structured patterns which and precisely
reproduced during each cell division. Diatom cell walls consist of inorganic
amorphous hydrated silica. In addition, certain organic components can
be found which are closely attached to the inorganic material. These organic
components are supposed to play a key role in the formation of highly
structured cell walls.
Within this project our group analyses the process of biosynthesis
of amorphous silica in diatoms in cooperation with the Biochemistry
(Prof. Dr. Karl-Heinz van Pée). Especially by using modern
solid-state NMR spectroscopic techniques, we investigate the silica
metabolism in diatoms as well as the contribution of biomolecules
in process of silica deposition. For example, we studied the self-assembly
of polyamines (PA) by P-31 NMR spectroscopy. PA are organic molecules
which can be found in cell walls of diatoms. Changes of the chemical
shift and linewidth indicate the binding of phosphate to PA and
the aggregation of PA molecules. It is tempting to speculate that
the formation of PA clusters is a prerequisite for the formation
and design of diatom cell walls.