Polycationic Peptides from Diatom Biosilica That Direct Silica Nanosphere Formation

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Science  05 Nov 1999:
Vol. 286, Issue 5442, pp. 1129-1132
DOI: 10.1126/science.286.5442.1129

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Diatom cell walls are regarded as a paradigm for controlled production of nanostructured silica, but the mechanisms allowing biosilicification to proceed at ambient temperature at high rates have remained enigmatic. A set of polycationic peptides (called silaffins) isolated from diatom cell walls were shown to generate networks of silica nanospheres within seconds when added to a solution of silicic acid. Silaffins contain covalently modified lysine-lysine elements. The first lysine bears a polyamine consisting of 6 to 11 repeats of the N-methyl-propylamine unit. The second lysine was identified as ɛ-N,N-dimethyl- lysine. These modifications drastically influence the silica-precipitating activity of silaffins.

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