Materials Science

Small and Strong

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Science  24 Nov 2006:
Vol. 314, Issue 5803, pp. 1218
DOI: 10.1126/science.314.5803.1218c

The intricate silica cell walls fabricated by the unicellular algae known as diatoms are highly porous and are produced with high fidelity. Diatoms have therefore been viewed as a possible platform for nanostructured materials synthesis. Hildebrand et al. have probed cell wall synthesis in the nanostructured form of Thalassiosira pseudonana, an organism whose genome has recently been sequenced. They studied a series of structural intermediates to unravel the chemical formation sequence and to ascertain when certain proteins come into play. At the earliest stages, they observed an outline of the valve with silica ribs radiating from the center. The rim structure then thickens, followed by a thickening of the rest of the valve structure. As the ribs form and fuse together, they give rise to a nanoporous structure with larger, more irregular pores than those formed earlier in the process. These observations confirm that the structure of T. pseudonana has been optimized to maximize strength with minimized material requirements, all the while allowing for the uptake and efflux of metabolites during this process. The authors hope in the long term to replicate and control many of these features through modification of the genome or through mixing of an appropriate array of polypeptides and polyamines to foster silica polymerization in vitro. — MSL

J. Mater. Res. 21, 2689 (2006).

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