Specialized proteins can control the growth of biogenic mineralized tissue. Using specific recognition motifs, proteins bind and control the formation of mineral facets and can thereby grow the intricate mineral morphologies found in Nature. Particularly fascinating is the mineralization of high fidelity silica nanostructures in the frustules of diatoms. Within these unicellular algae, proteins called silaffins play a crucial role in the molecular biomineralization machinery. Material scientists are trying to harness the concepts used by diatoms and other species to more efficiently fabricate mineral nanostructures and aim to formulate design rules for material precipitation to understand the mechanisms of protein–silica interactions. We found that designed peptides containing lysine and leucine side chains (LK peptides) can mimic silaffin’s role in the formation of diverse biosilica nanomaterials. By choosing the periodicity of L and K sites, these peptides were designed to fold into helical or beta-sheet structures and represent simplified model systems to study the effect of protein folding on mineralization (1,2). Using surface sensitive sum frequency generation (SFG) vibrational spectroscopy we have studied the interactions of LK peptides with biosilica surfaces. We determined how LK peptides fold at the silica–water interface and found that interfacial folding and solution aggregation is crucial for the silica morphology: spheres, rods and wire-type structures were produced – depending on LK folding. Side chains also actively participate in the mineralization process. We probed the side chain structure of LKs in contact with silicic acid solution and observed increased ordering of charged lysine side chains during the formation of biosilica, indicating their involvement in silica nucleation. Combined with TEM measurements and MD simulations the SFG studies provide important new details of peptide-driven silica formation. (1) J. E. Baio, A. Zane, V. Jaeger, A. M. Roehrich, H. Lutz, J. Pfaendtner, G. P. Drobny, T. Weidner Diatom Mimics: Directing the Formation of Biosilica Nanoparticles by Controlled Folding of Lysine-Leucine Peptides Journal of the American Chemical Society, accepted. (2) A. Zane, C. Michelet, A. Roehrich, P.S. Emani, G.P.Drobny, Silica Morphogenesis by Lysine-Leucine Peptides with Hydrophobic Periodicity, Langmuir, 2014, 30 (24), pp 7152–7161.

Biomimetic silica formation probed at the molecular level using SFG spectroscopy and MD simulation

249th National Meeting (2015)

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