= Silaffin
A <silaffin> is a modified <peptide> associated with the <silica>-containing <cell wall> of a <diatom>. <Silaffins> help explain how an <organism> can promote mineral formation under conditions compatible with a living <biological cell>.
In a 1999 experiment, purified <silaffins> extracted from <diatom> walls rapidly generated networks of <silica> nanospheres when added to a silicic-acid solution. Chemical analysis identified modified <lysine> residues, and the modifications affected silica-precipitating activity.<Polycationic peptides from diatom biosilica that direct silica nanosphere formation by N. Kröger and others>[Abstract, Science 286, pp. 1129–1132]{ref} The result demonstrates direct promotion of mineral deposition by an organic component. It does not alone explain the full patterned geometry of a <frustule>: producing mineral and organizing it into an elaborate wall are distinct experimental questions.
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