Biosilica Nanofabrication in Diatoms: The Structures and Properties of Regulatory Silaffins

Diatoms are a large group of unicellular microalgae encased by silica cell walls that exhibit species-specific, mostly porous micro-and nanopatterns. Previously, from the diatomCylindrotheca fusiformisunique phosphoproteins (termed silaffins) and unusually long polyamine chains (termed LCPA) have been identified and implicated in silica formation. However, analysis of the general role of silaffins in species-specific silica morphogenesis has been hampered by lack of data about silaffins from other diatom species. Recently, we have isolated the five major silaffins from the diatomThalassiosira pseudonanaand aided by the genome data available from this organisms we were able structurally und functionally characterize these molecules. These data clearly support the hypothesis that silaffins play an important role in the nanofabrication of diatom biosilica. The basic insights into the mechanism of biomineral morphogenesis by silaffins and LCPA suggest future pathways for the fabrication of nanostructured minerals by synthetically available polymers.