Morphology of artificial silica matrices formed via autosilification of a silaffin/protein polymer chimera.

Protein polymers (long-chain proteins in which a specific amino acid sequence "monomer" is repeated through the molecule) are found widely in nature, and these materials exhibit a diverse array of physical properties. One class of self-assembling proteins is hydrophobic-polar (HP) protein polymers capable of self-assembly under the appropriate solution conditions. We generated a chimeric protein consisting of an HP protein polymer monomer unit, EAK 1 (sequence n-AEAEAKAKAEAEAKAK-c), and a silaffin peptide, R5 (sequence: n-SSKKSGSYSGSKGSKRRIL-c). First identified in diatoms, silaffins represent a class of proteins and peptides capable of directing silica precipitation in vitro at neutral pH and ambient temperatures. The EAK 1-R5 chimera demonstrated self-assembly into hydrogels and the ability to direct silica precipitation in vitro. This chimera is capable of generating silica morphologies and feature sizes significantly different from those achievable with the R5 peptide alone, indicating that fusions of silaffins with self-assembling proteins may be a route to controlling the morphology of artificially produced silica matrices.