Silica biotemplating by self-assembling peptides via serine residues activated by the peptide amino terminal group

Self-assembling biological materials increasingly serve as templates for the binding of inorganic materials and fabrication of composite nanowires, tubes, etc. with important applications in nanobiotechnology. We have previously reported the use of a self-assembling octapeptide building block as scaffold for the systematic introduction of metal-binding residues, namely cysteines, at the first two amino acids within the sequence (Kasotakis et al., Biopolymers 2009, 92, 164-172). We have also reported unexpected behavior of serine within the octapeptide NH₂ − NSGAITIG − CONH₂( (Asparagine-Serine-Glycine-Alanine-Isoleucine-Threonine-Isoleucine-Glycine) in nucleating gold and platinum nanoparticles. Herein, we report that this serine residue is instrumental in nucleating silica nanoparticles on the surface of the self-assembled fibrils from TEOS (tetraethyl orthosilicate) precursors. We carried out a systematic investigation of the adjacent functionalities and we propose that this serine residue is rendered abnormally nucleophilic through proton abstraction by the N-terminal amino group of the peptide. Peptides with a threonine or a cysteine residue at position 2 are also able to nucleate silica nanoparticles. We propose that rationally designed self-assembling peptides bearing hydroxyl groups adjacent to free amine functionalities could be used for targeted templating of biogenic and even nonbiogenic oxides.