Design and Characterization of Peptide-Calcite Biomineralization Systems

Elizabeth A. Specht1, Sarah Schrier1, David L. Masica2, and Jeffrey J. Gray3. (1) Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, (2) Program in Molecular and Computational Biophysics, Johns Hopkins University, Baltimore, MD 21218, (3) Chemical and Biomolecular Engineering; Program in Molecular and Computational Biophysics, Johns Hopkins University, Baltimore, MD 21218

Naturally evolved proteins are capable of controlling the growth and morphology of hard tissues in living systems through specific interactions with solid surfaces. A better understanding of the interactions at the protein-solid interface could enable the design of proteins that can bind non-biological materials, allowing for materials fabrication with nanoscale precision. Our group uses a computational approach to design peptides that bind calcite. These peptides vary in charge and hydrophobicity, and their lengths range from 10 to 20 amino acids. Once designed, the peptides are synthesized using Fmoc solid-phase automated peptide synthesis, purified by HPLC, and verified for purity by ESI mass spectrometry. To test their interactions with calcite, we add these designer peptides to solutions of growing calcite crystals, varying the peptide concentration and the calcite crystal nucleation time prior to peptide addition. The effect of the peptides on crystal morphology is analyzed using light microscopy and scanning electron microscopy, and the secondary structure of the peptides is characterized by circular dichroism spectroscopy. The peptides alter crystal growth and morphology with varying degrees of specificity depending on their sequence. These experimental results are used in the design of subsequent rounds of peptides, in an effort to increase their specificity and achieve better control over crystal morphology.