The role of phosphopeptides in the mineralisation of silica

We investigated the silicification activity of hyperphosphorylated peptides in combination with long-chain polyamines (LCPA). The bioinspired in vitro silicification experiments with peptides containing different amounts of phosphorylated serines showed structure-activity dependency by scaling of the amount and morphology of the silica precipitate. Our study provides an explanation for the considerable metabolic effort of diatoms in the synthesis of hyperphosphorylated poly-cationic peptides such as natSil-1A1. The efficient late-stage phosphorylation of peptides yielded a synthetic heptaphosphopeptide which resembles the silicification properties of natSil-1A1. Opposed to that, unphosphorylated poly-cationic peptides or LCPA require concentrations above 1 mM for silicification. Hyperphosphorylated peptides maintained a linear dependence between the amount of dissolved peptide and the amount of precipitated silica in the concentration range below 1 mM. Under mildly acidic conditions and short precipitation times the concentration of added LCPA determined the size of the silica spheres.